Roseworthy South Australia September 1991

SPONSORS

ABERFOYLE RESOURCES LIMITED, D.S. T. 0., F. H. FAULDING & CO. LTD., SOLA OPTICAL, TECHSEARCH INCORPORATED, TIOXJDE AUSTRALIA PlY. LTD.

CONTENTS

PREFACE

ACKNOWLEDGEMENTS

PARTICIPANTS NOT PRESENTING PAPERS

PROGRAMME

SEMINAR PROGRAMME

ABSTRACTS (in order of presentation)

PAGE

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3

4

5

6

11

PREFACE

This is the sixteenth of a s~ries of infonnal meetings originally initiated by the daunting duo of Bob Hunter and Tom Healy some twenty years ago. From these early times when only a handful of people were involved, the meetings have grown to accommodate one hundred or more participants.

The foundation philosophy of these meetings is that postgraduate students and the occasional new "Post-Doc" should be able to present their work 10 an audience of their peers, academic supervisors and a few CSIRO and industry scientists.

Informality is the key and students are expected to withstand considerable constructive criticism of their work both during their presentation and afterwards over drinks. Another feature of these meetings is that the organisers invite one or more distinguished scientists to talk about their work and, perhaps more importantly, the philosophy behind it

At the 16th Meeting it is a pleasure to welcome Dr. Ian Pitman, Research Director of Fauldings, as well as Professor Abraham ("Avi") Marmur from Technion in Israel. This balance of industrial and academic research views is of importance to all colloid and interface scientists.

Meetings have been hosted by research groups in Melbourne, Sydney, the A.N.U., Bendigo an.d S.A.I.T. The Sixteenth Meeting is being held at Roseworthy, as was the Twelfth, but on this occasion S.A.I.T. has metamorphosed into the University of South Australia.

I should like to extend my thanks to all part1c1pants at the Meeting and, particularly, to Belinda Braggs and Marianne Montalti for their sterling efforts in organising the affair.

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ACKNOWLEDGEMENTS

The following organisations have provided substantial financial support for this Conference and their contributions are wannly acknowledged:

Aberfoyle Resources Limited

D.S.T.O.

F.H. Faulding & Co. Ltd.

Sola Optical

Techsearch Incorporated

Tioxide Aust. Pty. Ltd.

Paree Vergis, Graphic Designer (design on shirts and cover)

Obviously the individual attendees have also contributed financially to the running of the Conference as have their host Institutions. This support is invaluable.

Guests of Honour

Professor Abraham Marmur, Technion, Israel

Dr. Ian Pitman, Research Director, F.H. Faulding & Co.

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PARTICIPANTS NOT PRESENTING PAPERS From ANSTO

Dr. Rose Amal

From Comalco: Dr. Janine Godfrey

From C.S.I.R.O.: Dr. Neil Furlong Dr. Nonnan Geddes Dr. Barry Matthews Dr. Len Warren Mr. George Georgaklis Ms. Elke Paschinger Mr. Darrell Wells

From ICI : Mr. Steven Marangos Ms. Jennie Saunders

From Kodak Aust. Pty. Ltd.: Dr. Mauhew Lay

From Sola Optical: Mr. David Diggins

From Tecbnion Israel: Prof. Avi Marmur

From Curtin University: Mr. Patrick Fernandez

From Australian National University:

Dr. Calum Drummond Dr. Stephen Hyde Dr. Richard Pashley Mr. David Atkins Ms. Marilyn Karaman

From Flinders Unh·ersity: Dr. Bruce Baker

From Monash University: Prof. Barry Hart Dr. Ian McKinnon \1.r. Herman Hvang

From RMIT: Mr. John Taylor

From University of Melbourne:

Prof. Thomas Healy Prof. Lee White Dr. Steve Camie Dr. Derek Chan Dr. Jilska Gregory Dr. Franz Grieser Dr. Peter Scales Dr. Yee-Kwong Leong Mr. Rod Binnington Ms. Enda Kelly Ms. Meredith Patterson Mr. Dean Turner

From University of New South Wales:

Prof. Russell Howe

From University of South Australia:

Prof. John Ralston Prof. Roger Smart Dr. Daniel Fornasiero Dr. Robert Hayes Dr. Clive Prestidge Dr. Pawittar Arora Mr. Minghua Mao Mr. Angus Neuing Mr. Michael Pietrobon Mr. Andrew Robinson

From University of Sydney: Prof. Robert J. Hunter Dr.GregWa.rr

From University of

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Queensland: Dr. Geoff Barnes Dr. Gwen Lawrie !v1s. Bronwyn Elliott

~

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PROGRAMME H>R 16TH AUSTRALIAN COLLOID AND SURFACE CHEMISTRY STUDENT CONFERENCE ROSEWORTHY AGRICULTURAL COLLEGE CAMPUS

Mondav Tuesday Wednesday 2:lrd Srpll'n1brr 241h September 25th September

Tlrnr & Vrnur Timr Activity Venur Timr Activity A,· t1\·i1J·

Kc~i:\ua11u11 DR 7.45-8.45 8rcalcfa.s1 DR 7.45-8.45 Breakfa..1 7-10 pm (Bus SUJ)plicd HI 9.()(J-9.30 Welcome by L 9.00-10.30 Seminars ~rm!( people Prof. from aiapon) . RalstonOl 10.30-10.45 Morning tea

Nihblc s and 9.30-10.30 Seminars L 10-45-12.30 Seminars dnn.l..s 1•ovitlnJ.

10.30-10.50 Mornin g tea L 12.30-1.30 Lwich(BBQ)

I0.50-12.30 Scmman. L 1.30-6.00 •social Af1cmoo11

12.30-1.J0 Lunch DR 4.00-4 .30 Af1cmoon tea

1.30-3 .15 Scmmars L (Roscwonhy)

3.15-~.45 Af1crnoon tea L 7.30 Fonnal Dinner onwards Speaker:

3.45-5.50 Seminars L Dr. Pitmar.<2>

6.30-8.00 Dinner DR

8.()()-11.00 Social T Evcmng

L • L« turc ·n ,rairc ; DR = Dmin!( Room: BA = 11110 ,\rca: T = Campus Tavern

• So,:1.11 Aftt·m1. ... m E11hcr (I )

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llarossa Valley Tow Sport > Crickcl. tf..•nms or swimming on Campus .

C I) llof John Ralsion, University of South Austral ia i!.J Dr. Ian P11man. Research D11cc1or , Faulding n i Prof t\v1 ~tumw. Techrnon, Israel ~

Thursday Friday 26th September 27th Seplember

Vrnur Tim, Activity Vrnur Tlmr Activity

DR 7.45-8.45 Breakfast DR 7.45-8.45 Brcalcfast

L 9.00-10.35 Seminars L 9.00-10.30 Seminar,

L 10.35-11.00 Morning tea L I 0.30-10.50 Morning Tea

L I 1.00-12.55 Seminars L I 0.50-12.35 Seminars

BA 12.55-2.00 Lunch DR 12.35- Lunch (BBQ)

2.00-3.25 Seminars L (Bus supplied for transpon

3.25-3.45 Afternoon u:a L 10 airpon) BA

3.45-5.30 Seminars L

DR 6.00-7.30 Dinner DR

8.00-9.00 Lecture: Prof. L Marmur())

9.15-11.30 Social evening T (Nibbles provided)

Vrnur

DR

L

L

L

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16TH AUSTRALIAN COLLOID & SURFACE STUDENT CONFERENCE

TUESDAY 24TH

9.00 - 9.30

DISPERSIONS

ROSEWORTHY, S.A.

SEPT. 24 - 27, 1991

SEMINAR PROGRAM

Welcoming Address - Prof. John Ralston

Chair: Assoc. Prof. Bob Hunter

9.30 - 9.45 Bronwyn Battersby (Uni. of Queensland) "Nuclear Overhauser effect studies on phospholipid vesicle suspensions"

9.45 - 10.00 Belinda Braggs (Uni. of South Australia) "The electrical double layer properties of lcaolinite"

10.00 - 10.15 Ross deKretser (Uni. of Melbourne) "Rheological properties of slurried coal mine lailings"

10.15 - 10.30 Tina Hines (Monash Uni.) "Investigation of the behaviour of copper added to the Tambo River by Wilga Spring: possible adsorption onto iron hydroxyoxides"

10.30 - 10.50 MORNING TEA

10.50 - 11.15 John Cleaver (Uni. of Sydney) "Aggregation behaviour of Alumina: a non-DLVO phenomenon"

11.15 - 11.40 Laurence Meagher (AN.U.) "The rheology of concentraled quartz suspensions containing calcium ions"

11.40 - 12.05 Mirjana Prica (Uni. of Melbourne) "lnlerfacial properties of Zirconia in aqueous electrolyte solutions"

12.05 - 12.30 Tony Roberts (A.N.U.) "Fractal growth models"

12.30 - 1.30 LUNCH

I .30 - 1 .45 Peua Liddell (Uni. of Melbourne) "The influence of processing on lhe rheology of Ti02 pigment ~ suspensions"

l .45 - 2.00 Jennifer McCulloch (Uni. of Melbourne) -im.crfacial phenomena in solvent cxuaction"

6

2.00 - 2.15 Robert Mun (Uni. of Melbourne) "1be fonnulation of coal-water-fuels"

2. I 5 - 2.30 Mark Zimsak (Uni. of Melbourne) "Flow of semidilute glass fibre suspensions in tubular entry flows"

2.30 - 2.45 Sean Le Count (Uni. of South Australia) "Compositional and structural alteration of pynhotite surfaces in solution : XPS and XRD studies"

SURFACTANTS IN SOLUTION

Chair: Dr Greg Warr

2.45 - 3.00 Simon Godkin (C.S.I.R.0.) "Novel sucrose-based surfactants"

3.00 - 3.15 Kathryn McGrath (A.N.U.) "Polymerisable surfactants"

3.15 - 3.45 AFTERNOON TEA

SURFACTANT ADSORPTION

Chair: Dr Greg Warr

3.45 - 4.00 Frances Keary (Uni. of Melbourne) "Polymers at interfaces"

4.00 - 4.25 John Morgan (Uni. of Sydney) "Selectivity and kinetics in ion flotation systems"

4.25 - 4.40 Marianne Montalti (Uni. of South Australia) "Interaction of Dixanthogen with pyrite"

4.40 - 5.05 Lisa Evans (Uni. of Sydney) "Principles governing the collectivity of surfactants in ion flotation"

5.05 - 5.20 Peter Weissenborn (Curtin Uni.) "Wheat starch as a selective flocculant for ultrafine iron ore"

5.20 - 5.35 Stephen Grano (Uni. of South Australia) "Measurement of rest potentials in the presence of adsorbing molecules"

5.35 - 5.50 Irene Baker (C.S.I.R.0.) "Viscosity Behaviour of Silica/Surfactant Dispersions"

WEDNESDAY 25TH

THIN FILMS Chair: Dr Neil Furlong

9 .00 - 9.25 Nicholas Bolonkin (A.N.U.) "Improved Langmuir-Blodgett films using novel techniques and surfactants"

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9.25 - 9.50 Frank Caruso (Uni. of Melbourne) "Spectroscopic analysis of thin organic films"

9.50 - 10.15 Jonathon Ennis (A.N.U.) "Local and global: undulations of charged bilayers"

10. I 5 · 10.30 David Hewitt (Uni. of South Australia) "Thin film drainage at the solid-water-air interface"

10.30 - 10.45 MORNING TEA

10.45 - 11.10 Robert Hall (Uni. of Melbourne) "Monolayers of thermotropic liquid crystals"

11.10 - 11.35 Annette Murphy (Uni. of Melbourne) "The effect of the deposition conditions on the structure of Langmuir Blodgett films in an aqueous environment"

11.35 - 12.00 Matt Trau (Uni. of Melbourne) "Evanescence vs. Effervescence"

12.00 - 12.15 Thomas Horr (Uni. of South Australia) "Determination of coating thickness by contact angle measurements"

12.15 - 12.30 David Scoberg (C.S.I.R.O., Uni. of Melbourne) "Semiconductor particles in L-B films"

12.30 - 1.30 LUNCH

THURSDAY 26TH

PARTICLE & SURFACE INTERACTIONS

Chair: Prof. Tom Healy

9.00 - 9.25 Tim Senden (A.N.U.) "Direct measurement of forces on collodial particles with the Atomic Force Microscope"

9.25 - 9.50 Erica Wanless (A.N.U.) "Surface force measurements in nonpolar liquids between hydrocarbon surfaces"

9.50 - 10.05 Paul Rider (Uni. of Sydney) "The dynamic mobility of interacting colloidal panicles"

10.05 - 10.20 Mark Rutland (A.N.U.) "pH-Dependent interactions of mica surfaces in aqueous dodccylammonium / dodecylamine solutions"

10.20 - 10.35 Aris Theocharides (Uni. of Melbourne) "\1ean field theory of ballistic aggregation"

10.35 - I 1.00 MORNING TEA

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SURFACE CHARACTERIZATION & MODIFICATION

Chair: Prof. Roger Smart

11.00 - 11.15 Michael Logan (Uni. ofN.S.W.) "Carbonyl complexes in pillared clays"

11.15 - 11.30 Peter Murphy (Flinders Uni.) "Characterization of acid sites on solid catalysts by DRIFT spectroscopy"

11.30 - 11.45 Yongbai Yin (Uni. of Sydney) "Chemadsorption of remnant oxygen on active carbon in ultra-high vacuum"

11.45 - 12.10 David Kehoe (Uni. of South Australia) "Siloxane modification of glass fibre surfaces"

12.10 - 12.35 Ewen Silvester (Uni. of Sydney) "Kinetics of chalcopyrite (CuFeS:i) oxidation"

12.35 - 12.50 Ken Jackson (Uni. of N.S.W.) "Characterisation of oxide films on titanium"

12.50 - 12.55 Ken Jackson (Uni. of N.S.W.) "FTIR microscopy of zeolites"

12.55 - 2.00 LUNCH

INSTRUMENTATION & METHODS

Chair: Dr Geoff Barnes

2.00 - 2.15 Wendy Barron (Uni. of Melbourne) "Mechanisms of action of the streaming current detector"

2.15 - 2.30 Yasuhito Ebara (Tokyo Inst. of Tech.) "Detecting protein adsorption using quartz crystal microbalance"

2.30 - 2.45 Peter Garside (Uni. of Sydney) "Eleccroacoustic measurements on model colloids and electrolytes"

2.45 - 3.00 Deidre Hotchin (Monash Uni.) "FFF-ICP-MS : A new hyphenated analytical method"

3.00 - 3.25 Alice Lamb (Uni. of Sydney) "High frequency electroacoustic measurements for model colloids"

3.25 - 3.45 AFTERNOON TEA

3.45 - 4.00 Byung-Sub Kim (Uni. of South Australia) "Scanning Tunneling Microscope (STM) imaging of organic compounds on the surface of highly oriented pyrolytic graphite (HOPG)"

4.00 - 4.25 Linda Maidme.nt (Uni. of Sydney) "Fluorescence depolarisation in microemulsions"

-US - 4.50 Chih-Ming Chen (Uni. of Sydney) "Rheology of three-componem microemulsions"

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4.50 - 5.00 Brendan Sinnamon (Uni. of Queensland) "Applications of piezoelectric crystals in adsorption studies"

5.00 - 5.15 Myhuong Nguyen (Monash Uni.) "Characterization of polydisperse polymers using Thennal Field-Flow Fractionation"

5.15 - 5.30 Reshmi Shanna (Monash Uni.) "Characteriz.ation of bacteria by sedimentation field-flow fractionation"

FRIDAY 27TH

MICELLES I MICROEMULSIONS & POLYMERS IN SOLUTION

Chair: Dr Franz Grieser

9.00 - 9.15 James Gunning (Uni. of Melbourne) "Dynamics of disordered chains: effect of damping and various types of discxdering"

9.15 - 9.30 Rachel Hobson (Uni. of Melbourne) "Electrostatic surface potential measurements of mixed surfactant micelles in urea solutions.

9.30 - 9.45 Andrea O'Connor (Uni. of Melbourne) "Free flow electrophoresis of proteins"

9.45 - 10.00 Peter Pieruschka (A.N.U.) "Physical aspects of the localised random wave model of bicontinuous microem ulsions"

10.00 - l0.15 Dr Ingrid Soderberg (A.N.U.) "Phase properties and structure of a monoglyceride-sucrose-water system"

10.15 - 10.30 Eric Weisser (Uni. of Melbourne) "Polymer flooding in enhanced oil recovery"

10.30 - 10.50 MORNING TEA

10.50 - 11.15 Philip Ashburner (Uni. of Sydney) "Raman studies of aqueous micellar solutions"

11.15 - 11.30 Jane Wright (Uni. of Melbourne) "Diffusion in dilute polymeric liquids"

11.30 - 11.45 Xiaodong Zhang (A.N.U.) "The stability of bicontinuous cubic phases"

11.45 - 12.10 Scott Buckingham (Uni. of Sydney) "Auractive ionic micelles"

12.10 - 12.35 ChristopherGarvey(Uni.ofSydney)

12.35

"Counterion adsorption: An imponant determinant of micellar interfacial Structllre"

LUNCH

10

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NUCLEAR OVERHAUSER EFFECT STUDIES ON PHOSPHOLIPID VESICLE SUSPENSIONS

B.J. Battersby and G.T. Barnes (Department of Chemistry, University of Queensland)

The ability of phospholipids to organize spontaneously into bilayer structures when dispersed in water accounts for their important structural role in biological me~branes and their usefulness as model membrane systems.

Phospholipids in vesicles produce single, high-resolution 3 l P nuclear magnetic resonances, which, by irradiation at the proton resonance frequencies, exhibit an increase in the integrated intensity due to proton decoupling. This is known as the nuclear Overhauser effect (NOE). Studies on the NOE provide information about the structure, environment, and dynamic properties of the headgroup in phospholipid vesicles.

The present work relates to a series of studies by N.L. Gershfeld [Biochimica et Biophysica Acta, 988 (1989) 335] on the spontaneous formation of a single bilayer state at a critical temperature, T*. At T* this unilamellar structure appears simultaneously in both the surface film and the dispersion. In both the film and the dispersion there are large differences between the properties above and below this temperature.

Observation and measurement of the NOE in 3 l P NMR spectra of phospholipid dispersions at temperatures in the region of T* is used for understanding the changes in conformation and molecular motion in the headgroup region of the phospholipid.

This data is supported by observations made by other techniques such as electron and optical microscopy, contact angle, and surface film measurements.

**NOTES**

C,\c.\ ~½~ 'e:.'t-\ ~

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THE ELECTRICAL DOUBLE LAYER PROPERTIES OF KAOUNITE

Belinda Braggs (School of Chemical Technology, University of South Australia)

The electrical double layer properties of Kaolinite have been studied using microelectrophoresis and surface charge titration. It was found that the zeta potential did not change with ionic strength and the isoeleclric point occurred at pH = 3. A model is proposed to account for these observations.

Organosilanes (trimethylchlorosilane and chlorodimethyloctyldecylsilane) were used to modify the surface of Kaolinite and the resulting electrical double layer properties

• were also studied. It was found that the organosilanes altered the electrical double layer properties of the Kaolinite surface.

**NOTES**

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RHEOLOGICAL PROPERTIES OF SLURRIED COAL MINE TAIUNGS

Ross de Kretser (Department of Chemical Engineering, University of Melbourne)

The rheological properties of slurried coal mine tailings have been investigated using a concentric cylinder viscometer and a capillary rheometer. Yield stress measurements have also been undertaken using the vane technique. The slurried tailings have been shown to exhibit yield stress and shear thinning (pseudoplastic) behaviour. The yield stress and shear stresses under steady shear have been observed to vary by over an order of magnitude for solids contents ranging from 30 to 50% and the slurry viscosities have exhibited drops of an order of magnitude with a similar magnitude of increase in shear rate. Work is at present focusing on the effect of surface chemistry properties on the rheology of these slurries, i.e. Electrophoretic mobility, Zeta potential and pH., and how they can be altered to aid in the dewatering and subsequent disposal of these wastes.

**NOTES**

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INVESTIGATION OF THE BEHAVIOUR OF COPPER ADDED TO THE TAMBO RIVER BY WILGA SPRING : POSSIBLE ADSORPTION ONTO IRON HYDROXYOXIDES

Tina Hines (Water Studies Centre, Monash University)

The behaviour of copper and zinc added to the Tambo River, situated in the Victorian Highlands, by an acidic, metal rich spring (Wilga Spring) was studied under very low flow conditions. The source of the metals is microbial oxidation of a copper-zinc orebody known to exist adjacent to the river. The studies identified that the major inputs from the Spring entered the Tambo River through the river bed over a distance of approximately 150 m.

The mechanism generally thought to be responsible for heavy metals from acidic mine drainage is the oxidation of Fe (II) to form amorphous iron hydroxyoxide (FeOOH), followed by rapid adsorption of Cu onto this FeOOH with subsequent loss of FeOOH and its associated Cu from the water column to the sediments. The direct adsorption of Cu onto the sediments is also possible, particularly if the sediment particles are coated with FeOOH.

Analysis of the water samples taken during the low flow conditions (5 Feb. to 10 May, 1991) showed a considerable proportion of copper (50-70%) was associated with the particulate fraction. The particulate copper concentration in this region is largely controlled by adsorption onto iron hydroxyoxide surfaces associated with the particulate matter (ratio of particulate iron to particulate copper is around 50-90% ). The sediments in the 150 m downstream of Wilga Spring have a high ratio of Cu/Fe (5-40%, wl/wt) compared with ratio of 0.5-0.7% in sediments taken upstream of Wilga Spring. A heavy orange-brown floe has been observed adhering to rocks in the river bed just below the Spring over a distance of around 150 m. Analysis of the floe samples, which has an organic Cu/Fe (50-70%) compared with the corresponding value found for sediments. This suggests that precipitation and/or adsorption onto iron hydroxyoxide particles or sediments and possibly adsorption onto organic surfaces are probably processes controlling the behaviour of c.;ppcr in this region.

**NOTES**

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AGGREGATION BEHAVIOUR OF ALUMINA - A NON-DLVO PHENOMENON

John Cleaver (School of Chemistry, University of Sydney)

The aggregation behaviour of aluminium oxide particles in electrolyte solutions has been studied using dynamic and static light scattering. The rate of increase in hydrodynamic diameter over time varies for different salt concentrations as expected in an electrostatically stabilised colloidal system. There is no critical coagulation concentration evident for the monovalent or divalent salts tested. For the monovalent salts, high concentrations (ranging from 100 mM to 900 mM) were required for slow to rapid aggregation. Much lower concentrations (3000-fold less) of divalent salts are required for comparable rates of aggregation. c;_,,"'\f>"----\c.. - -'""'°"'-

The structure of the aggregates was investigated through static light scattering studies, which indicate the aggregates are fractal objects. Scanering exponents, or fractal dimensions, are obtained from the static light scattering experiments, and these can be used to elucidate the nature of packing of the aggregate. It has been found that the scattering exponent of the aggregate is dependent upon the anion effecting the aggregation. With the chloride anion scattering exponents of the order of 2.2 ± 0.04 were observed; with the sulphate anion, scattering exponents of the order of 1.8 ± 0.04 were found. This suggests a more compact packing has occurred when the chloride anion has affected the aggregation than when the sulphate anion is responsible.

** N01ES **

1 ~8'A-f '\' "'-j'f~0 \ : ,,..,.,

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1 v1YoS~ .\.f 71

THE RHEOLOGY OF CONCENTRATED QUARTZ SUSPENSIONS CONTAJNING CALCIUM IONS

Laurence Me.agher (Department of Chemistry, The Australian National University)

The rheology of 46.8 volume percent ground quartz suspensions has been investigated using a concentric cylinder viscometer, modified so as to keep the suspension continually stirred.

When calcium ions are present in such a suspension, the rheological behaviour is modified from that of a dispersed, slightly shear-thickening suspension to that of an aggregated, shear-thinning suspension. This effect becomes more marked as the pH of the suspension is increased.

The results of this study will be discussed in terms of the interactions between the particles comprising the suspension.

**NOTES**

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THE INTERFACIAL PROPERTIES OF ZIRCON/A IN AQUEOUS ELECTROLYTE SOLUTIONS

Mirjana Prica (School of Chemistry, University of Melbourne)

There has been a resurgence of scientific interest in zirconia CZr02) as an advanced ceramic because of the improved physical performance of the green bodies from which it is made. This project aims to understand the properties of the Zt02 -aqueous electrolyte interface with the view to improve the processes leading to the production of the ceramic material.

Fundamental electrokinetic, electroacoustic and charge titration experiments showed that the pH(iso-electric point)=pH(zero point of charge)=7.4 ± 1.0 in KN03 and

KCI04 solutions at 25°C. No salt dependence of the zeta potential (') was observed. This was attributed to the 'dehydrated' nature of the surface caused by the high calcination temperature of the Zr02 sample. An attempt was made to regenerate the surface hydroxyl groups by soaking the Zr02 in water over prolonged periods of time, as well as by plasma etching. The pH(iso-electric point) shifted erratically and no change in , with salt concentration was noted.

Currently, tritium-exchange experiments are being developed in order to obtain NH (the number of hydroxyl groups on the surface). These results will provide insight into the nature of the Zr0:2 surface and help to elucidate its anomalous properties.

** NOIBS **

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FRACTAL GROWTH MODELS

A.P. Roberts (Department of Applied Mathematics, The Australian National University)

A broad introduction to the physics of pattern fonnation will be presented. The models fall into two classes, stochastic and detenninistic, which model a wide range of physical processes from the formation of physical aggregates to the growth of snowflakes. Results from ongoing computer investigations into the models of diffusion limited aggregation and dielectric breakdown will be briefly presented.

••NOTES••

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THE INFLUENCE OF PROCESSING ON THE RHEOLOGY OF Ti02 PIGMENT SUSPENSIONS

Petra Liddell (Department of Chemical Engineering, University of Melbourne)

Titanium Dioxide pigment particles are coated with white inorganic oxides. The suspensions are prepared by adding purified water to the pigment sample, and dispersing with concentrated nitric acid. The suspensions are then sonicated until they are smooth and homogeneous.

The rheology of three coated pigments at two different stages of production was investigated. Shear stress was measured as a function of shear rate on the Bohlin rheometer. The main objective was to observe the effect of pH, solids concentration and process history on the flow characteristics of the suspensions. A range of pH from 4 to 10 was studied, whereby aqueous KOH was used to increase the pH. In this pH range measurements were made on both the flocculated and dispersed state. Three different solids concentration were studied for each pigment ranging from 10% to 30% volume solids. Pigment samples supplied by Tioxide were from the filter discharge and from the final packed product Two types of filter discharge were studied - the Hoesch plate and frame filter, and the Eimco press belt filter.

••NOTES••

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JNTERFACIAL PHENOMENA JN SOLVENT EXTRACTION

Jennifer McCulloch (Department of Chemical Engineering, University of Melbourne)

Commercial chelating reagents are commonly used for the extraction of metal ions from aqueous solutions. These extractants react with the metal ions in aqueous solution and form uncharged complexes which are soluble in the organic phase. The mechanism of this extraction was at fust assumed to be reaction of the ion and reagent in the aqueous phase, and subsequent movement of the neutral complex into the organic phase. Another mechanism more recently postulated is that the reaction is an interfacial one, with the reagent molecules at the interface reacting with the ions in solution. A way of measuring an interfacial reaction is using attenuated total reflectance (ATR) spectroscopy. In this work, ATR is used to measure interfacial concentration changes in the copper/Kelex 100 extraction system. These measurements are used to determine rate constants for this reaction.

**NOTES**

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THE FORMULATION OF COAL-WATER-FUELS

Robert Mun (Advanced Mineral Products Centre, University of Melbourne)

The concept of using coal as a substitute for oil is a well studied idea, though there is no hard and fast rules upon how to create a coal based fuel. The options are: liquify, coal-oil, coal-water, coal-methanol, or any combination of the aforementioned. The cheapest option, and thus the most likely to be economic is coal-water. Thus, a brief excursion into how coal-water-fuels are prepared, and the problems that arise in their preparation and use will be made. The problems, presented for a rheological point of view, originate from the nature of the surf ace of the coal, and the use of additives is required to overcome them. Additive selection however, causes its own dilemas, due to the wide variety available, and the lack of knowledge about the mechanisms by which they act.

**NOTES**

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FLOW OF SEMIDILUTE GLASS FIBRE SUSPENSIONS IN TUBULAR ENTRY FLOWS

Mark Zimsak (Department of Chemical Engineering, University of Melbourne)

The flow behaviour of 'short' glass fibre suspensions in entry flow is of importance in polymer processes, for example, in injection moulding. Consideration will be given to the results of semidilute fibre suspensions in inelastic Newtonian fluids in laminar entry flow. Streakline photographic techniques have been used to observe the recirculating vortex present. Effects of fibre concentration and fibre aspect ratio have been investigated. The experimental work yet to be carried out will consider semidilute fibre suspensions in ideal elastic 'Boger' fluids in laminar entry flow.

** NOIBS **

22

COMPOSITIONAL AND STRUCTURAL ALTERATION OF PYRRHOTITE SURFACES IN SOLUTION : - XPS AND XRD STUDIES

Sean Le Count (School of Chemical Technology, University of South Australia)

Ground pyrrhotite (Fe1-xS) surfaces oxidised by exposure to air, water and deoxygenated perchloric acid solution were analysed using X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). In air or water, XPS examination reveals amorphous layers containing carbonate and sulphate species, iron (Ill) oxide/hydroxides, and an underlying iron-depleted surface with a S (2p) doublet shifted 1.0 - 1.8 e V higher than the sulphide peak. XRD results from acid treated surfaces show that the surface partly rearranges to a crystalline, defective tetragonal pyrite-like structure in which linear chains of Sn atoms have an S-S distance similar to elemental sulphur (Sg) but the XPS S(2p) BE is still 0.2 - 0.6 eV less than Sg. The chemical forms of Fe and S in the surface layers and the possible implications of these for flotation response will be discussed.

**NOTES**

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NOVEL SUCROSE-BASED SURFACTANTS

Simon Gookin (CSIRO, Division of Chemicals & Polymers, Melbourne)

Currently the surfactant industry relies heavily on petrochemical feedstocks. With ihe forecast shortages of petroleum-based products and their inevitable escalation in cost, the need for surfactants derived solely from renewable raw materials is obvious. Sucrose-based surfactants offer a possible alternative. They are already being used in the cosmetic and food industries because of their non-toxicity and ~on-allergenicity. However, the present cost of synthesising these products limits their viability in applications that require large volumes of surfactant, but have a low profit margin.

The results of a systematic investigation of the surface activity. self-assembly, wetting and detergency of some current commercial and novel sucrose-based surfactants will be presented.

**NOTES**

24

1

POLYMER/SABLE SURFACTANTS

Kathryn M. McGrath (Department of Applied Mathematics, The Australian National University)

I have been looking at a series of polymerisable surfactants with the aim of being able to polymerise the phases which they form, in the hope of forming a bicontinuous structure which could be used as a template. The surfactants which I have looked at in particular are Allyldimethyldcxlecylammonium Bromide (ADAB) and Dodecyldimethylammoniumethylmethacrylate Bromide (DDAM).

**NOTES**

25

POLYMERS AT INTERFACES

Frances Keary (Department of Mathematics, University of Melbourne)

The statistical mechanics of a non-interacting polymer adsorbed on an impenetrable wall can be investigated using standard mathematical techniques. We consider the polymer as a chain of non-interacting beads. The aim of this talk is to outline some of the techniques used, particularly those used to derive the density of beads off the wall for the cases of one polymer and many polymers adsorbed on the wall. We hope to extend this model to incorporate a mean field interaction.

**NOTES**

-, .... -,

26

SELECTNJTY AND KINETICS JN JON FLOTATION SYSTEMS

John Morgan (School of Chemistry, University of Sydney)

Ion flotation is an absorptive bubble technique for solutions, analogous to conventional flotation, which is capable of cheaply extracting a desired ionic species from very dilute solutions. This talk discusses recent results in the understanding of the kinetics of the process and the nature of the selectivity between different anions using cetyltrimethylammonium as the collector.

**NOTES**

rcJ...e o\ 1 c<..cro~ t c...) ,i

27

INTERACTION OF DIXANTHOGEN WITH PYRITE

Marianne Montalti (School of Chemical Technology, University of South Australia)

Pyrite, FeS2, is a common constituent of base-metal ore deposits, and the flotation and depression of this mineral is important for the extraction of valuable components.

One of the most commonly used collector for the flotation of pyrite is xanthate. The pyrite-xanthate· system has been investigated for over 50 years and yet there is still much controversy to the mechanism and processes involved.

Xanthate is known to be unstable in aqueous solutions and the decomposition products of xanthate and their rates of formation are dependent on the environmental pH. However, UV-visible spectroscopy studies has shown that when xanthate is in contact with pyrite, derivatives of xanthate are formed in solution and their relative concentrations are also pH dependent.

Pyrite behaves as a catalyst for the formation of these xanthate derivatives, which include dixanthogen, monothiocarbonate and perxanthate. Fourier Transform Infrared studies have clearly detected dixanthogen on the pyrite surface. Pyrite is capable of floating readily in the presence of xanthate because the dixanthogen generated on the mineral's surface is hydrophobic.

In order to investigate the pyrite-xanthate mechanism intensively, the behaviour of each xanthate derivative in the presence of the mineral needs to be investigated. Only dixanthogen and its behaviour with pyrite will be discussed by presenting flotation, UV-visible spectroscopy and electrophoretic mobility results.

0 NOTES**

28

PRINCIPLES OF GOVERNING COLLECTIVITY OF SURFACTANTS IN ION FLOTATION

Lisa Evans (School of Chemistry, University of Sydney)

Ion flotation is currently being used as a technique for removing anionic metal complexes from solution using an ionic surfactant. The process involves passing air bubbles through the solution and forming a froth which is concentrated in both metal ions and surfactant molecules. The concept of using a surfactant with more than one charged head group per molecule in order to collect more metal ions per mole of surfactant will be discussed. The relationship between collection/flotation behaviour and surface properties will be examined.

,, **NOTES**

29

WHEAT STARCH AS A SELECTIVE FLOCCULANT FOR ULTRAFINE IRON ORE

Peter Weissenborn (School of Applied Chemistry, Curtin University)

As reserves of high grade lump iron ore in the Pilbara District of W estem Australia become low there will be an increasing need to treat lower grade fine iron ore. Currently iron ore as fine as 20 µm can be upgraded using conventional processing

techniques. However, iron ore less than 20 µm and usually containing up to 45-50% iron is discarded as tailings. A potential method for upgrading this ultrafine iron ore involves selective flocculation of the valuable iron minerals. Such a process has been in commercial operation at the Tilden Iron Ore Mine, USA, since 1974. This presentation will focus on, (i), the development of a laboratory scale selective flocculation process applied to the ultrafine Pilbara iron ore and, (ii), the overall mechanism of selective flocculation.

The ultrafine iron ore contained primarily hematite, goethite, kaolinite and quartz. A flocculant was required to selectively flocculate only the hematite and goethite particles from a dispersion of all mineral particles. Wheat starch was chosen as the best flocculant, after testing a large range of commercially available flocculants. Optimisation of the selective flocculation regime involved studying parameters such as pH, wheat starch concentration, dispersant concentration, stirring rate and pulp density. All parameters were optimised to obtain maximum grades and recoveries. Under optimum conditions concentrate grades ranged between 56 and 58% iron (feed grade of 46.6% iron) with iron recoveries between 70 and 80%.

Investigation of the mechanisms of adsorption of wheat starch to hematite and flocculation of the iron oxides has recently commenced. The study has revolved around the chemistry of the amylose and amylopectin components of starch and their individual behaviour in adsorption and flocculation. Amylopectin appears to be significantly more active during adsorption and flocculal.ion than amylose.

**NOTES**

30

MEASUREMENT OF REST POTENTIALS IN PRESENCE OF ADSORBING MOLECULES

Stephen Grano (School of Chemical Technology, University of South Australia)

The rest potential (steady state galvani potential) of various mineral sulphide electrodes have been investigated as a function of pH, anionic surfactant (collector) concentration, and metabisulphite (MBS) concentration and oxygen concentration. The effect of surface preparation of the electrode surface on potential was also investigated.

It was found that a galena (PbS) electrode potential was more dependent on collector concentration than either a pyrite (FeS2) or pyrrhotite electrode (Fe1-xS). By contrast the pyrite and pyrrhotite electrode potentials were more dependent on the MBS concentration than the galena electrode. Mechanisms of the observed effects are discusred

**NOTES**

3 t

VISCOSITY BEHAVIOR OF SIUCA!SURFACTANT DISPERSIONS

Irene Baker (C.S.I.R.O., Division of Chemicals and Polymers, Melbourne)

Suspensions of silica in refractive index matched glycerol/water mixtures were studied. Addition of various surfactants was found to have a strong effect on the viscosity of these systems.

With increasing concentration of nonionic (Cl2E8) or cationic (DTAC) surfactant the viscosity increased sharply to a maximum and fell sharply to nearly the initial value. Subsequent increasing concentration of anionic surfactants to the negative silica surface is not favorable, the comparatively minor effect of the anionic surfactant on viscosity is consistent with this explanation.

Surface tension measurements were used to determine the cmc's of these surfactants in the glyceroVwater mixture used. Contact angle measurements on hydrophilic and hydrophobic quartz enabled some confirmation of the proposed adsorption behavior.

**NOTES**

32

IMPROVED LANGMU/R-BLODGEIT FILMS USING NOVEL TECH AND SURFACTANTS

Nicholas Bolonkin (Department of Applied Mathematics, T University)

New surfactant molecules have been designed for the purpose of engineering Langmuir-Blodgett (LB) films with a high degree of order in their structure. These molecules were polymerizable so th the novel technique of polymerizing the surfactant monolayers before co · ng them onto substrates could be employed, instead of the usual techniq e which leads to films with a high degree of imperfection. The mol ules contained a rnacrocyclic ligand, not only for structural reasons, but also so at spectroscopic and electrochemical studies of monolayers and multilayers uld be carried out, with a view to creating ion-selective electrodes andmemb

**NOTES••

33

..

SPECTROSCOPIC ANALYSIS OF THIN ORGANIC FILMS

Frank Caruso (Depanmem of Physical Chemistry, University of Melbourne)

Two-dimensional diffusion has been investigated in polymerizable air-water monolayer films by studying the fluorescence quenching of a lipoidal pyrene derivative [N-( 1-pyrenesulphonyl)dipalmitoy 1-L-a-phosphatidylethanolamine] by two amphiphilic quenchers [N,N-octadecyld.imethylamine and 4-(N,N-dimethyl-N­hexadecyl)ammonium-2,2,6,6-tetramethylpiperidine-1-oxyl, iodide]. The results have been analyzed using the continuum model for two-dimensional diffusion. The lateral diffusion coefficients were found to decrease wilh increasing surface pressure.

**NOTES**

34

LOCAL AND GLOBAL: UNDULATIONS OF CHARGED BILAYERS

J. Ennis and A. Fogden (Department of Applied Mathematics, The Australian National University)

In analysing 'undulation forces' in multilamellar systems and the globally preferred structures in cubic phases, it is often necessary to include both long-ranged electrostatic forces and short-ranged steric ones. We solve a perturbation problem for a rippled bilayer composed of short-chain surfactants with charged head-groups. Variations of electro! yte concentration and charge density, and the steric contributions from the head-groups and the chains are all considered, and their effects on the membrane rigidity are analysed. At low electrolyte concentrations, we then demonstrate the difference between local and global approaches to minimising the free energy.

**NOTES**

+

,.

35

THIN FILM DRAINAGE AT THE SOLID-WATER-AIR INTERFACE

David Hewitt (School of Chemical Technology, University of South Australia)

The rate by which a thin aqueous film drains between a bubble and a mineral particle is a central problem in the froth flotation process. For example, it is not known what the influence of contact angle on the drainage rate might be, nor at what distanee the hydrophobic force influences the drainage rate.

We have studied the evolution of an aqueous film between a bubble and both hydrophilic and hydrophobic quartz surfaces. An interferometer was used to measure the thin film drainage rate of aqueous films constrained between an air bubble and a quartz surface.

An increase in either salt concentration or hydrophobicity had the same effect; an increase in the rate of drainage at the boundary ring of the draining film, accompanied by a decrease in the rate of drainage at the centre of the film. Attempts have been made to explain the behaviour observed in terms of the existing models developed to describe the profile of the draining film.

~ ~-~~' \,'---o-L<... ~\o~.J

••NOTES••

til~ (..--\.a~ .r e,,~ ........ t\<­

-.,)'""""" '\' '°"''~~\<~~.

36

('\.(o.~,J

MONOLAYERS OF THERMOTROP/C UQUID CRYSTALS

Robert Hall (School of Chemistry, University of Melbourne)

Liquid crystalline phases of surfactant molecules are generally associated with lyotropic behaviour, however some thennotropic liquid crystals are surface active. Surface pressure studies of air-water monolayers of the thennotropic LC 4'-dodecyl-4-cyanobiphenyl (12CB) in arachidic acid (AA) and oleic acid (OA) were undertaken. Analysis of the surface pressure data using Crisp's phase rule reveals 12CB is miscible in OA and immiscible in AA, over a wide range of mole fractions of 12CB. Fluorescence emission spectroscopy supports this result, with observed excimer fonnation at low mole fractions of 12CB in OA modelled by a statistically random distribution of 12CB in the monolayer plane.

**NOTES**

37

STRUCTURE OF L.-\.VGMUIR BLODGETT FILMS IN AN AQUEOUS ENVIRONMENT

Annette Murphy (School of Chemistry, University of Melbourne)

Langmuir Blodgett films consisting of one layer of cadmium arachidate (CdAa) covered by a layer containing 10% of the polarity sensitive probe, dansyl dihexadecylamine (DDHA) and CdAa, were investigated in an aqueous environment. By monitoring the emission spectra of the DDHA over a period of time, it was found that the angle of the substrate to the advancing barrier during the deposition process, greatly influenced the structure of the film. When the substrate was parallel to the advancing barrier, the wavelength maximum of the DOHA emission spectrum bi ue shifted from 485 nm to 4 70 nm over several weeks. This suggested that the dansyl group had slowly migrated from a fairly polar environment to an hydrophobic one. When the substrate was perpendicular to the advancing barrier, the wavelength maximum of the DDHA emission spectrum blue shifted from 500 nm to 470 nm over a few days, indicating a comparatively rapid migration of the dansyl group to an hydrophobic environment

**NOTES**

38

~

EVANESCENCE VS. EFFERVESCENCE

Man Trau (School of Chemistry, University of Melbourne)

Structural detennination of adsorbed layers (e.g. polymers or Langmuir-Blogett films) at the solid/liquid or solid/air interface is an area which has long attracted much attention and remains at the core of colloid and surface science research. Experimentally, detailed information about the structure of the adsorbed layer is still extremely difficult to obtain and is often only partially accessible via a handful of existing teehniques: e.g., small angle neutron scattering, neutron reflectivety, ellipsometry and nuclear magnetic resonance. This talk will describe a new spectroscopic technique which has the capacity to obtain detailed structural infonnation from very thin adsorbed layers. The technique utilizes evanescent waves, generated by total internal reflection at the solid/liquid or solid/air interface, to interact with absorbing chromophores in the adsorbed layer. Structural infonnation is obtained by varying the depth of penetration of the evanescent wave into the surrounding medium, which is controlled by the angle of incidence of reflection and by the refractive index mismatch between the solid phase and that of the surrounding medium. Results obtained for the adsorption of model polyelectrolytes onto silica will be presented.

**NOTES**

39

~

DETERMINATION OF COATING THICKNESS BY CONTACT ANGLE MEASUREMENTS

Thomas Horr (School of Chemical Technology, University of South Australia)

The Cassie equation is discussed in relation to the use of contact angle measurements to quantify the adsorption density, chain length or orientation of organic molecules on surfaces. It is known that the Cassie equation can describe the measured contact angle of water on a silica surface coated with up to a monolayer of TMS. Application of the Cassie equation to contact angle measurements on surfaces with different coatings is discussed in relation to literature results. The Cassie equation is found to offer an explanation to describe the measured contact angle values obtained by organic modifiers on surfaces.

**NOTES**

40

SEMICONDUCTOR PARTICLES IN L-B FILMS

David Seaberg (CSIRO, University of Melbourne)

Small particles of lhe semiconductor chalcogenides (CdX; X= S, Se, Te) were incorporated into multilayer surfactant films by exposing lhe transferred film to lhe appropriate chalcogenide gas. The resultant particles were small enough to show size-quantization effects. The size of the particles could be reduced by using a mixed surfactant monolayer in conjunction with an inert ion diluent in the subphase. Mixed chalcogenide semiconductor particles could be formed by exposing a lighter cadmium chalcogenide to a gas of a heavier chalcogenide, but heavier chalcogenides could not be displaced by lighter ones. Such "Q-state" semiconductor particles possess optical non-linear third-order properties lhat are of interest in many areas of optics and opto-electronics.

** N01ES **

41

DIRECT MEASUREMENT OF FORCES ON COLLOIDAL PARTICLES WITH THE ATOMIC FORCE MICROSCOPE

Tim Senden (Department of Applied Mathematics, The Australian National University)

The Atomic Force Microscope (AFM), a close cousin of the Scanning Tunneling Microscope (STM), has already demonstrated its usefulness as a tool for surface scientists. Unlike the STM, the AFM does not require a conducting sample and is easily used in aqueous environments. Operated as a surface imaging tool the AFM can resolve surface features less than a nanometre apart, with similar vertical resolution giving . true 3D surface information. The instrument is designed to resolve forces as small as picoNewtons and so is ideally suited to the measurement of interfacial forces. Force detection is via the deflection of a weak cantilever to which a wide variety of surfaces may be attached, for example, colloidal particles. Presented is a description of the instrument together with the new technique enabling surface force measurement on almost any solid material.

**NOTES**

42

SURFACE FORCE MEASUREMENTS IN NONPOLAR LIQUIDS BEIWEEN HYDROCARBON SURF ACES

Erica Wanless (Department of Applied Mathematics, The Australian National University)

The Surfaces Forces Apparatus is being used to investigate systems consisting of two LB deposited hydrocarbon monolayers interacting across a nonpolar liquid. At this stage two important questions are under consideration. Firstly, the effect of the deposition pressure, and secondly the effect of the presence of water, on the interaction measured between the two monolayers.

**NOTES**

43

THE DYNAMIC MOBILITY OF INTERACTING COUOIDAL PARTICLES

Paul Rider (School of Chemistry, University of Sydney)

Due to recent advances in the field of electroacoustic measurements, it is now possible to measure the electrophoretic mobility of colloidal particles in suspensions of arbitrary concentration using alternating electric fields in the megahertz range. This mobility is referred to as the dynamic mobility to distinguish it from the mobility measured in static electric fields. This dynamic mobility depends on the size and charge (zeta potential) of the particle. The

~ conversion of dynamic mobility measurements in concentrated suspensions into particle size and charge infonnation requires a theory that talces particle interactions into account. The first step in developing a theory for concentrated suspensions is a study of the interaction of two particles. In this paper I will discuss the interaction of two identical spheres, the dynamic mobility of the spheres, and the implications of these results for concentrated suspensions.

**NOTES••

44

PH-DEPENDENT INTERACTIONS OF MICA SURFACES JN AQUEOUS DODECYLAMMONIUM I DODECYLAMINE SOLUTIONS

Mark Rutland , Asa Waltermo and Per Claesson (Department of Applied Mathematics, The Australian National University)

The adsorption of a hydrolyzable surfactant, dodecylammonium chloride, and interactions between layers thereof, has been studied as a function of pH using the surface force apparatus. At low pH the surfaces undergo charge reversal as dodecylammonium ions adsorb to form a sparse monolayer. At pH 8-9, adsorption of neutral dodecylamine molecules becomes important, rendering the monolayer more compact with a thickness close to the length of an extended molecule. A hydrophobic attraction is observed between the surfactant monolayers. At pH 9.5 -10.3 a bilayer forms on each surface. The double-layer force decreases gradually with increasing pH and disappears at pH 10.3. At this and slightly higher pH­values a multilayer gradually builds up on the surface. At pH-values around 12 the multilayer build-up is prevented by a recharging of the adsorbed layer. Both the adsorption behaviour and the interactions between the layers are reversible with respect to changes in the pH.

**NOTES**

-45

MEAN F/EW THEORY OF BALUSTIC AGGREGATION

Aris Theocharides (Department of Mathematics, University of Melbourne)

Numerical simulation is conducted of unidirectional ballistic aggregation. The evolution of the growing interface is investigated. A model based on the theory of evolution of planar curves is presented.

** NOlES **

46

CARBONYL COMPLEXES IN PILLARED CLAYS

M.B. Logan+, R.P. Cooney* and R.F. Howe+ (*Chemistry Department, University of Auckland and +Department of Physical Chemistry, University of New South Wales)

The adsorption and decomposition of transition metal carbonyl complexes is an established route for introducing transition metals into zeolites and other microporous materials. In this paper, we describe the use of the carbonyl methods to load metals into aluminium pillared montmorillonite clays (Al-PILC). Our objectives were to study the chemistry of the complexes in the clays, and to characterise the metal species produced on decomposition.

The Al-PILC were synthesised and characterised using conventional literature methods. Adsorption of transition metal carbonyl complexes (e.g. Mo(CO)6, Fe(CO)5) from the vapour phase was followed by gravimetric adsorption measurements and infrared spectroscopy. The complexes are adsorbed intact between the layers of the AI-PILC at room temperature. Decomposition occurs on heating; the initial loss of carbonyl ligands is partially reversible, but the final stages of decomposition involve irreversible oxidation of the transition metal by hydroxyl groups, as determined by XPS and EPR spectroscopy.

The chemistry of the metal complex: clay systems will be compared with that of the analogous zeolite materials, and the catalytic potential of these systems discussed.

**NOTES**

47

CHARACTERIZATION OF ACID SITES ON SOLID CATALYSTS BY DRIFT SPECTROSCOPY

Peter Murphy (School of Physical Sciences, Flinders University of South Australia)

The characterization of acid sites on solid catalysts has been investigaled by diffuse reflectance infrared fourier transform spectroscopy (DRIFI} The catalysts are exposed to pyridine in an environmental chamber in order to detect acid sites. Results so far show the ability to distinguish between Lewis and Bronsted acid sites. Conversion of Lewis to Bronsted sites has been observed in the presence of water-· vapour. The catalysts under investigation include : W03/Al203 , W03/Silica Gel, Mo03/A1203, Mo03'Silica Gel and silica alumina.

** N01ES **

48

CHEMADSORPTION OF REMNANT OXYGEN ON ACTIVE CARBON IN ULTRA-HIGH VACUUM

Yongbai Yin (Department of Applied Physics, University of Sydney)

Remnant gas adsorption over a long period on an active carbon surface in ultra-high vacuum (better than lx 10-8 torr) can be observed by using the quartz crystal microbalance (QCM) technique. This remnant gas adsorption can cause "hysteresis" in the adsorption and desorption isotherms. It is found that the unknown gas is adsorbed on high energy sites of the surface. The time dependence of the remnant gas adsorption shows a number of Elovich linear ranges.

Isothermal adsorption of water on this material indicates that the unknown gas is oxygen. The oxygen chemadsorption on this surface results in an increase of water adsorption sites in the range of low relative pressures. No sharp increase in adsorption occurs at high relative pressures due to small external surface area of this material.

---------------.. NOTES••

49

..

SILOXANE MODIFICATION OF GLASS FIBRE SURFACES

David Kehoe (School of Chemical Technology, University of South Australia)

The interactions between silanes and glass fibres have been well studied over the past twenty years. Their importance as 'Coupling Agents' between various polymer matrices and glass fibres is well documented. Siloxanes, in principal, should also be capable of functioning as 'Coupling Agents'. However, their use in this application, has not been generally accepted. The reasons behind this are not so well documemed.

This study compares the 'binding' to E-glass fibre of siloxanes with 'analogous' silanes. Atomic concentrations before and after a 50 nm 'etch' were analysed by XPS (X-ray Photoelectron Spectroscopy), and these results used as the basis of this comparison.

**NOTES**

50

THE KINETICS OF CHALCOPYRITE OXIDATION

Ewen Silvester (School of Chemistry, University of Melbourne)

The oxidation kinetics of "ultra-small" particle size chalcopyrite sols have been investigated using spectroscopic teehniques. The results give new insight into the stoichiometry of the oxidation process, and indicate a distinct change in the kinetics beyond the first monolayer of reaction. For the first monolayer, the rate of oxidation is shown to be dependent on the redox overpotential applied by the oxidant For strong oxidants, the oxidation reaction is of the fonn;

CuFeS2 + 5 H20 ~ Cu(OH)2 + Fe(OH)3 + 2S0 + 5 H+ + 5 e·,

while for weak oxidants a copper sulphide phase is an initial product.

Beyond the first monolayer, the rate of reaction is controlled by the de-sorption of sulphur-oxy anions from the particle surface, which is attributed to the charge balance requirements of the reaction.

**NOTES**

51

CHARACTERISATION OF OXIDE FILMS ON TITANIUM

K.T. Jackson 1 and J.B. Metson2 (lDepartment of Physical Chemistry, University of New South Wales, 2Department of Chemistry, University of Auckland)

The use of titanium and its alloys as bioimplant materials is now a relatively mature technology. It is clear that the biocompatibility of these materials is particularly good relative to other metal based systems, and this has resulted in increasing use of titanium based implants, particularly in oral surgery. There is however, no general agreement on the reasons for the success of titanium based

, materials in this role and the mechanism of osseointegration of such material. Thus we have sought to investigate the specific nature of oxide surfaces on commercially pure (CP) and Ti 6%Al 4% V (Ti64), the most commonly used materials in implant and aerospace applications, as a function of the mode of preparation and post-treatment of the oxide film. Such knowledge is important, both in improving implant reliability, and ultimately in materials selection of implants.

Oxide films were grown anodically under a range of conditions, from a UHV environment to anodisation in H2SO4 and H3PO4 and the resulting surfaces investigated by X-ray photoelectron spectroscopy, Auger Electron spectroscopy, Secondary Ion Mass Spectroscopy, Laser Raman spectroscopy and FfIR spectroscopy. Of particular interest was how the anodically grown oxide films differ from native oxide layers and ultimately, how this affects the binding of biomolecules to the implant surface.

••NOTES••

52

FTIR MICROSCOPY OF ZEOUTES

K.T. Jackson and R.F. Howe (Department of Physical Chemistry. University of New South Wales)

lnfrared spectroscopy has been extensively used to characterise zeolite catalysts and to identify adsorbed species. The addition of an FTIR microscope onto a spectrometer allows good quality FfIR spectra from zeolite single crystals as small as 20 microns. This allows the study of hydroxyl groups in acid zeolites. the Al-0 and the Si-0 stretching modes of the zeolite lattice. and the structures of organic polymers generated within the zeolite pores from adsorbed alkenes as well as polarisation studies giving orientation information about species observed.

••NOTES••

53

MECHANISMS OF ACTION OF THE STREAMING CURRENT DETECTOR

Wendy Barron (School of Chemistry, University of Melbourne)

Successful use of streaming current detectors, or SCD's by hundreds of industrial users, mostly in the USA, provides clear empirical evidence that the device successfully measures particle charge characteristics in aquatic suspensions. Yet a fundamental understanding of the device's operation has lagged behind its 3.pplication.

The method of operation of the SCD and its use in industrial applications will be discussed briefly. The two surfaces involved in the streaming current measurement are Teflon and polypropylene. Streaming potential measurements have been made using a flat-plate streaming potential apparatus from which the zeta potential show that the surfaces are negatively charged over the pH range 3-10. The SCD response when using selected particles with well established electrokinetic behaviour will be shown to compare favourably with their expected behaviour. Zeta potentials and SCD response for selected particles will be compared and the results with some instrument modifications will be discussed.

•• N01ES ••

54

~

DETECTING PROTEIN ADSORPTION USING QUARTZ CRYSTAL MICROBALANCE

Y asuhilO Ebara (Dept. of Biomedical Engineering, Tokyo Institute of Technology)

A Q.C.M. (Quartz Crystal Microbalance) consists of a quartz crystal sandwiched between gold or silver electrodes. When materials adsorb onto the electrodes, the Q.C.M.'s frequency decreases in proportion to its mass. The Q.C.M. offers a fast and simple alternative to the traditional method of optical or radio-labelling. Using this device, the adsorption of behaviour of various compounds (odorants, surfactants, drugs, proteins, liposomes, virus', etc.) to lipid multilayers insitu, have been observed. In this talk the behaviour of protein adsorption onto lipid monolayer and lipid multilayer surfaces will be outlined.

The Q.C.M. electrode was brought into contact with the monolayer surface horizontally, and the change of Q.C.M. frequency and surface pressure after the injection of the proteins under the subphase were measured simultaneously. This information gives the adsorption state of the proteins. At low surface pressure, both the mass of the Q.C.M. and the surface pressure increased after protein injection. This indicates that the proteins penetrated the alkyl chain of the lipid monolayer. At high surface pressure, no change to the surface pressure was observed upon injection of the protein. In such cases, it seems that the protein and the lipid monolayer do not interact with each other. However, by using the Q.C.M. system, it was clear that the protein interacted with the hydrophilic group of the lipid at this high surface pressure. It was observed that the hydrophobicity of the protein was an important factor in the adsorption behaviour. The protein adsorbed monolayer was also transferred onto the Q.C.M. using the Langmuir­Bloggett method, and immobilized quantitatively.

**NOTES**

2 (_(,,, ~ E.. ~e---, -)"<.d' .

SS

'

ELECTROACOUSTIC MEASUREMENTS ON MODEL COLLOIDS AND ELECTROLYTES

Peter Garside (School of Chemistry, University of Sydney)

When an alternating electric field is applied to a solution of charged species, sound waves are generated. Conversely, when sound waves pass through such a solution, alternating electric fields are set up. In this talk I will present measurements of this effect for some electrolytes. Unlike the colloidal measurements, these results do not agree with the existing theory. Possible reasons for this discrepancy will be discussed.

**NOTES**

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1<."'

'C,.\.~~'""-'t\~ ~ ..... \at\~\.7

.. c.:>A- .J.. rp A. r u...

56

1l • ~le• c.~\..J:~l)'

~' "-~'- ~~111.,

'-'c\ ~s ..,.l • J. ~

FFF-ICP-MS: A NEW HYPHENATED ANALYTICAL METHOD

Deidre Ho1ehin (Water Studies Centre, Monash University)

Sedimentation field-flow fractionation (SdFFF) has been successfully used in the separation and characterization of colloids and particles. It is a nondestructive technique which serves to fractionate the particles on the basis of their effective mass to give a particle size distribution. Further infonnation about the sample can be gained if the eluent from the FFF is analyzed by sensitive analytical techniques. EDAX can give an indication of the elements present and electric microscopy can ascertain particle shape and topography. Elemental infonnation can be obtained by partnering SdFFF with inductively coupled plasma-mass spectrometry (ICP-MS). Direct on-line analysis by ICP-MS gives the quantities of elements present in discreet particle sizes. The information obtained by this procedure can be interpreted in tenns of the geochemistry of the particle. The method is also useful for surface adsorption studies where metals are adsorbed onto colloidal subsirates. Samples studied by this method include illite and kaolinite clays, and the suspended particulate mauer from the Darling and Yarra Rivers.

**NOTES**

57

HIGH FREQUENCY ELECTROACOUSTIC MEASUREMENTS FOR MODEL COLLOIDS

Alice Lamb (School of Chemistry, University of Sydney)

The behaviour of colloidal particles in suspension is strongly influenced by their electrokinetic properties at the solid-aqueous interface. A new technique for measwing the electrokinetic properties, such as the particle mobility and the related zeta-potential (~). for colloidal suspensions have recently been reported in the literature [l ,21. It is based on the generation of alternating sound waves in colloidal particles by the application of an alternating electric field at about 1 MHz, and this electroacoustic effect is defined as the Electrokinetic Sonic Amplitude (ESA). The underlying theory for this electroacoustic technique have been based on spherical colloids which are uniformly sized with smooth surfaces and thin double layers.

This study concentrates on the experimental verification of the O'Brien theoretical analysis of electroacoustic effects in colloidal suspensions. This involved comparing high frequency zeta-potential (i.e. electroacoustic) measurements on stable, monodisperse colloidal dispersions with zeta-potential measurements using

. microelectrophoresis (the conventional electrokinetic technique). Dispersions such as Co.bait Phosphate, Yttrium basic Carbonate and various commercial Titanium Dioxide samples were examined [21. Some of the problems associated with the measurements will also be presented.

References: Ll] O'Brien, R.W., J. Fluid Mech., 190, 71-86 (1988). L2] O'Brien, R.W., Lamb, A., Hunter, RJ., Midmore, B.R., Faraday Discuss

Chem. Soc., 1990, 90 (in press).

**NOTES**

58

1

SCANNING TUNNEL/NG MICROSCOPE (STM) IMAGING OF ORGANIC COMPOUNDS ON THE SURFACE OF HIGHLY ORIENTED PYROLITIC GRAPHITE (HOPG)

Byung-Sub Kim (School of Chemical Technology, University of South Australia)

STM has been claimed to enable real-space topographic imaging of surface atomic structure at high resolution. This technique can be applied to investigation of surface impurity and defect states of molecules or biological structures deposited on solid substrates. The application of STM to the solution of problems in the area of colloid and surface chemistry is however in its infancy. Graphite is being used as a substrate in our work as it provides a good unit cell image and a fresh surface readily after cleaving. The images of the graphite reveal a number of unusual

properties, for example it images only ~ carbon atoms on the surface and yields anomalous corrugation heights. In this presentation, the potential of STM to obtain information about the location and orientation of adsorbed molecules on solid surf aces will be discussed.

**NOTES**

59

FLUORESCENCE DEPOLARISATION IN MICROEMVLSIONS

Linda Maidment (School of Chemistry, University of Sydney)

The three component system water/DDAB/dodecane does not require any other additive to form stable microemulsions. We have taken a variable, the co-surfactant pentanol, and are studying its effects on the fluidity of the microemulsion interface using the innovative technique of fluorescence anisotropy. The probe pyrene is used to indicate the extent to which pentanol is present at the interface. The probe TMA-DPH is used to take anisotropy values which measure the amount of movement at the interface. Experimental evidence has shown that they are positioned within the microemulsion interface and that their fluorescence lifetimes are appropriate to the study. A study of this kind is able to tell us more about the structure and dynamics of microemulsion interfaces.

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60

RHEOLOGY OF THREE-COMPONENT MICROEMULSIONS

Chih-Ming Chen (School of Chemistry, University of Sydney)

The rheology of three component water/dodecane/didodecyldimethylammonium bromide (DDAB) microemulsions has been studied. Viscosities have been measured throughout the single phase microemulsion region have been determined in the low shear range. The relationship of this shear behaviour to the equilibrium structure of the liquid will be discussed, together with some interesting non­Newtonian behaviour observed at higher shear rates.

**NOTES**

61

APPLICATIONS OF PIEZOELECTRIC CRYSTALS IN ADSORPTION STUDIES

Brendan Sinnamon (Department of Chemistry, University of Queensland)

The project I am undertaking involves an investigation of the formation and properties of organic thin films on solid surfaces. Initially calcium stearate films were deposited onto a quanz slide via the Langmuir-Blodgett technique in order to gain an understanding of some of the difficulties involved and the mechanism by which deposition occurred. Once the experiment had been successfully completed and a greater knowledge of the preparation and mechanisms by which Langmuir­Blodgett films are deposited, deposition onto a piezoelectric quartz crystal (or more accurately a silver electrode attached to the quartz crystal surface} of a calcium stearate monolayer was attempted. A plot of change in frequency (kHz) versus number of layers of calcium stearate deposited could then be made where the resonance frequency of a quartz crystal is affected by the deposition an amphiphilic substance. An investigation of the deposition of other amphiphiles belonging to the lipophilic macrocyclic species onto the silver electrode via the Langmuir­Blodgett technique could now be investigated. Characterization of LB films is studied by the departure of the recorded frequency of the crystal from the resonance frequency which allows us to identify positively that deposition has occurred. The project has applications to the development of metal ion sensors.

**NOTES**

62

CHARACTERIZATION OF POLYDISPERSE POLYMERS USING THERMAL FIELD-FLOW FRACTIONATION

Myhuong T. Nguyen (Department of Chemistry, Monash University)

Thermal field-flow fractionation (ThFFF) is a subtechnique of the field-flow fractionation (FFF) family of elution methods recently developed for separation and characterization of macromolecules and particles. In ThFFF, thermal diffusion is utilized to effect retention of samples as they migrate down the channel under the influence of the solvent flow. The technique has been used to characterize a number of commonly used synthetic polymers such as polystyrene and polymethylmethacrylic (PMMA). One of the advantages of ThFFF is its ability to handle ultrahigh molecular weight (MW) polymers due to its open, unpacked channel and the purely physical field-flow interaction mechanism. However at present, the use of ThFFF to determine absolute MW data is confined to polymers which have narrow MWD standards available. Since, in ThFFF narrow molecular weight distribution (MWD) standards are needed to establish the relationship between the retention parameter A and the MW for the polymer-solvent combination before the molecular weight can be determined.

This work is an attempt to expand the usefulness of ThFFF to include polymers that do not have narrow MWD standards available. In this paper, the background theory of an approach that utilizes polydisperse polymer samples for calibration purposes will be outlined, some preliminary results will also be discussed as well as its extension to include the determination of parameters other than the MW of the polymer.

**NOTES**

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63

CHARACTER/'ZATION OF BACTERIA BY SEDIMENTATION FIELD-FLOW FRACTIONATION

Reshmi Shanna (Water Studies Centre, Monash University)

Sedimentation field-flow fractionation (Sd.FFF) is a method for purifying and providing mass or size distribution information on colloidal samples in the range 0.05 - 5 µm. SdFFF has several advantages over other particle characterization techniques, perhaps the most important being the fact that it is both a sizing and separation method. Thus it yields fractions for further characterization by other methods such as Electron Microscopy, Quasi-elastic Light Scattering, Epifluorescence Microscopy, etc .. Combining information from different methods in this way provides a means of obtaining detailed information about very heterogeneous samples. SdFFF is a gentle technique which should be suitable for fractionating delicate materials such as bacterial cells, viruses, viral DNA's and liposomes. Experiments are being conducted in our laboratory to demonstrate the applicability of SdFFF in the characterization and enumeration of bacteria Several cultured bacteria strains were selected for testing on the basis that they are easy to obtain and relatively uniform in size. Suitable experimental run conditions have been established for these bacteria and the use of both UV absorbance and fluorescence detectors have been assessed. Fluorescence detection has the advantage of being more sensitive, thus reducing the detection limit; and being specific for the stained bacteria which allows the bacterial mass to be recorded even if other inert particles are present in the eluting fractions.

The SdFFF methodology has many possible uses in aquatic microbial ecology. Not only should the technique provide a convenient method for the routine processing of samples to determine microbial biomass currently done by tedious optical microscopic methods, but also for the detailed characterization of both size and density.

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**NOTES**

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64

DYNAMJCS OF DJSORDERED CHAJNS EFFECT OF DAMPJNG AND VARJOUS TYPES OF DISORDING

James Gunning (Department of Mathematics, University of Melbourne)

The vibrational spectra of disordered damped systems is of interest to colloid researchers, since experimental spectra may reveal aspects of the structure of colloidal systems, as well as information about particle properties. This paper investigates the perturbative effects of various fonns of damping (Stokes, Rayleigh) and types of disorder on the vibrational spectrum of a linear chain of particles coupled by Hookean springs.

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65

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r

THE EFFECT OF THE DEPOSITION CONDITIONS ON THE ELECTROSTATIC SURFACE POTENTIAL MEASUREMENTS OF MIXED SURFACTANT MICEUES JN UREA SOLUTIONS

Rachel Hobson (School of Chemistry, University of Melbourne)

Surface tension measurements on 1-hexadecanol and 1-dodecanol in SM urea solution have been used to establish the formation of micelle / aggregate structures in this solvent. A description of how spectroscopic pH indicators, such as 4-hcptadecyl-7-hydroxycoumarin and the solvatochromic probe l-hexadecyl-5-hydroxyquinoline, can be utilized to determine the electrostatic surface potential in

" mixed sodium dodecyl sulphate/ 1-hexadecanol and sodium dodecyl sulphate/ 1-dodecanol micelles will be given. The long term plan is to compare these potential values with theorectical potentials calculated using the cell model.

**NOTES**

66

FREE FLOW ELECTROPHORESIS OF PROTEINS

Andrea O'Connor (Deparunent of Chemical Engineering, University of Melbourne)

Eleclrophoresis is a technique extensively used and understood in analytical-scale purifications and separations. Free flow electrophoresis has significant potential to be scaled up for economical industrial separations, but the understanding of this process is limited. There is no existing method to predict the efficiency of separations, largely because of a lack of quantitative information about the effects of the system conditions and of the interactions between the proteins themselves. The effects of the system conditions on the electrophoretic mobility of single proteins in solution and the investigation of multicomponent interactions in free flow electrophoresis will be discussed.

**NOTES••

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67

PHYSICAL ASPECTS OF THE WCALISED RANDOM WAV . BICONT/NUOUS MJCROEMULSJONS

P. Pieruschka and S. Marcelja (Department Ausualian National University)

The localised random wave descrip · of bicontinuous microemulsions introduces a wave envelope of characteris · rrelation length into a group of models based on the Berk model. We sho t the model predictions for bulk and film neutron­

. greemenl with experimental data. Further mathematical analysis yields astic energy and the entropy of the random wave system thus opening the ponunity to base model parameters on thermodynamic principles. The m · r shortcoming of the phenomenological Berk models is hence con · cingly moderated.

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68

PHASE PROPERTIES AND STRUCTURE OF A MONOGLYCERIDE -SUCROSE - WATER SYSTEM

Ingrid S&lerberg and Helena Ljusberg-Wahren (Department of Applied Mathematics, The Australian National University)

The phase behaviour of a sunflower oil, monoglyceride-sucrose-water system was studied at 300C. The different phases were identified by low-angle X-ray diffraction and polarization microscopy. The main feature of the phase diagram is the transition from a cubic phase to a reversed hexagonal phase (Hn) when sucrose is added to the monoglyceride-water mixture. A similar phase behaviour was also shown to occur for rnonoolein-sucrose-water, as well as in the corresponding systems when sucrose was replaced by trehalose, fructose and glucose, respectively.

The phase transition from a cubic phase to a Hu phase, when sugar is introduced to a monoglyceride-water system, corresponds to an increased average wedge shape of the lipid molecule. One explanation for this phenomenon is a structural change of the lipid caused by interaction between the sugar and the hydrated polar head group, thus reducing the interfacial area of the polar region at the contact zone with water.

**NOTES••

69

POLYMER FLOODING IN ENHANCED OIL RECOVERY

F.ric We~r {Deparunent of Chemical Engineering, Univemty of Melbourne)

Polymer flooding of oil fields is an economical method of enhancing oil recovery. Dilute polymer solutions are used to modify the interfacial properties of the chasing water flood to minimise fingering of the water through the oil bank. This process is prone to interfacial instabilities at the oil-polymer and polymer-water interfaces, resulting in viscous fingering effects. A review of studies that have been performed in packed and unpacked radial cells will be presented with particular emphasis on the relationship between viscous fingering and rheological properties of the polymer solutions.

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70

*RAMAN STUDIES OF AQUEOUS MICEUAR SOLUTIONS

Philip H. Ashburner (School of Chemistry, University of Sydney)

Spectroscopic analysis of the O-H stretching region of aqueous micellar solutions is undertaken. The aim is to monitor changes in the water network around the CMC for ionic and non-ionic surfactant systems with a view to the elucidation of some aspects of the thermodynamics of micellization. Further work will include attempts to correlate the effects of additives on the water structure with changes in the CMC.

**NOTES**

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71

• I)

DIFFUSION IN DILUTE POLYMERIC UQUIDS

Jane Wright (Depanment of Chemical Engineering, University of Melbourne)

Diffusion in dilute polymer solutions is of interest to many areas including biological systems, physiological processes, polymerisation and waste treatment. A number of experimental investigations of diffusion through dilute polymeric solutions have been published. Dilute polymer solutions are generally shear thinning and often elastic and significant confusion exists in regard to non­Newtonian viscosity and elasticity effects on the diffusion coefficient. The influence of the rheology of the solvent system on the diffusion process will be presented. Particular emphasis will be placed on discussion of those rare diffusion measurements where both the kinematic and rheological properties have been carefully controlled. A framework in which to conduct such controlled measurements will be proposed.

" **NOTES**

72

STABILITY OF BICONTJNUOUS CUBIC PHASES

Xiaodong Zhang and Stephen Hyde (Department of Applied Mathematics, The Australian National University)

A diversity of phases are observed to form in surfactant/water mixtures. In the theoretical prediction of the stability of phases, geometrical considerations, based on the bending energy of the interfacial film of surfactant molecules, are a crucial factor. For bicontinuous phases (including cubic phases) the interface may be modelled by a minimal surface, i.e. a surface of zero mean curvature. Here the bending energy of such an interface is calculated for a variety of known infinite periodic minimal surfaces of different topology and symmetry. Comparison of these bending energies then determines the most favourable aggregate geometry.

**NOTES**

73

AITRACTIVE IONIC MICELLES

Scott Buckingham (School of Chemistry, University of Sydney)

The phase separation of alkyltributylarnmonium halides with increasing temperature will be discussed. Particular attention shall be payed to the investigation and assignment of the intermicellar attractive potential necessary for phase separation. Tetradecyltributylammonium bromide, its chloride analogue and tetradecyltripentylammonium bromide solutions form the experimental basis of the discussion. Data from a broad spectrum of surfactant concentrations will be presented.

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74

COUNTER/ON ADSORPTION : AN IMPORTANT DETERMINANT OF MICELLAR INTERFACIAL STRUCTURE

Christopher Garvey (School of Chemistry, University of Sydney) - -

The sire, charge, and relative hydration of the coumerion of micellized surfactants has been found to play a role in detennining the shape, size and surface charge density of the micelle. Through the use of several complementary techniques it is hoped to gain a greater understanding of the mjcellar interface, where the influence of the counterion is the greatest. The techniques to be used aim at characterising the interface in tenns of the charge distribution, both the net charge at the interface (or surface charge density) and the charge density of the headgroups. The foundations of this work is the measurement of surface potential using an interfacially sited acid/base system. This work will be complemented by the measurement of aggregation numbers.

------------** NOlES **

75

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