imidazolium-modified clay-based abs nanocomposites: a comparison between melt-blending and...

POLYMERS FOR ADVANCED TECHNOLOGIES

Polym. Adv. Technol. 2008; 19: 1576–1583

ce.wiley.com) DOI: 10.1002/pat.1172
Published online 9 June 2008 in Wiley InterScience (www.interscien
Imidazolium-modified clay-based ABS nanocomposites:

a comparison between melt-blending and

solution-sonication processesy

M. Modesti1*, S. Besco1, A. Lorenzetti1, M. Zammarano2, V. Causin3, C. Marega3,

J. W. Gilman2, D. M. Fox4, P. C. Trulove5, H. C. De Long6 and P.H. Maupin7

1Department of Chemical Process Engineering, University of Padova, 35131 Padova, Italy2Building and Fire Research Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA3Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131 Padova, Italy4Department of Chemistry, American University, Washington DC 20016-8014, USA5Chemistry Department, US Naval Academy 572M Holloway Rd, Annapolis, MD 21402-5026, USA6Directorate of Chemistry and Life Sciences, Air Force Office of Scientific Research, Arlington, VA 22203-1768, USA7Office of Basic Energy Sciences, Office of Science, US Department of Energy, Washington, DC 20585, USA

Received 21 February 2008; Revised 25 March 2008; Accepted 25 March 2008

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Acrylonitrile--butadiene--styrene (ABS) nanocomposites containing imidazolium-modified mon-

tmorillonite have been prepared by melt-blending (MB) and solution-sonication in order to study

the effects of processing on the morphology and properties of the polymer/clay composites. The

structure-property relationships of the prepared composites have been studied by means of X-ray

diffraction (XRD), transmission electronmicroscopy (TEM),mechanical testing, dynamic-mechanical

analyses (DMA), thermal gravimetrical analyses (TGA), fluorescence probe confocal microscopy,

and fluorescence spectroscopy (FS). X-Ray and TEM show that both nanocomposites have a mixed

intercalated/exfoliated structure. Fluorescence probe confocal microscopy reveals that the sonicated

sample has a more homogeneous dispersion: this result is confirmed by the values of elongation at

break and flexural elastic modulus measured for the composites. Fluorescence spectroscopy has also

been used to investigate the distribution of clay in the composites and results indicate that clay layers

in ABS are preferentially located in the styrene-acrylonitrile (SAN) phase, independent of the

dispersion process used. Published in 2008 by John Wiley & Sons, Ltd.

KEYWORDS: ABS; imidazolium salts; solution processing; melt-blending; nanocomposites; Nile Blue A; fluorescence probe

INTRODUCTION

The production of polymer/organically modified layered

silicate (OMLS or clay) nanocomposites has been accom-

plished by several routes, including in situ polymerization of

monomer/clay intercalates, solution-intercalation, and melt-

compounding.1–4

ndence to: M. Modesti, Department of Chemical Processing, University of Padova, 35131 Padova, [email protected] is a U.S. Government work and is in the publicn the U.S.A.is work was carried out by the National Institute ofs and Technology (NIST), US Naval Academy, and USagencies of the US government, and by statute is notcopyright in the United States. Certain commercialt, instruments, materials, services, or companies arein this paper in order to specify adequately the

ntal procedure. This in no way implies endorsementendation by NIST, US Naval Academy, or the US Air

e policy of NIST is to use metric units of measurementublications, and to provide statements of uncertaintyginal measurements. In this document however, datanizations outside NIST are shown, which may includeents in non-metric units or measurements withoutty statements.

Melt-blending (MB) is by far the most common because it

involves the processing operations commonly adopted for

the parent polymers and does not require the use of organic

solvents; however, the high temperature, shear stress, and

local overheating induced by the shear itself can affect the

clay through thermal degradation of the organic modifier,

phase separation of the clay, and possible reduction in the

aspect ratio of the layered silicate.5,6

Low temperature processing techniques or OMLS with

enhanced thermal stabilities have been developed in order to

avoid thermal degradation of clay’s surfactant during the

preparation of the composite. The thermal degradation of

alkyl-ammonium-salts, commonly used as surfactant for

OMLS, becomes significant above 2008C,7 thus, the use of

clays in polymers requiring higher processing temperature is

challenging. Alternative clay surfactants, like imidazolium

or phosphonium salts, have been used in order to enhance

the thermal stability of OMLS.8,9 As a different approach, a

low temperature solution-intercalation process can be used

to avoid thermal degradation of OMLS. In the solution-

intercalation procedure, a solvent capable of dissolving

the polymer and swelling the clay is selected and a

well dispersed heterogeneous three-component mixture of

Published in 2008 by John Wiley & Sons, Ltd.

Imidazolium-modified clay-based ABS nanocomposites 1577

appropriate composition is prepared with the help of

heating, mechanical stirring, and/or ultrasonication. The

solvent can then be removed by evaporation or by

precipitation of the polymer/clay composite in a co-solvent.

The acrylonitrile–butadiene–styrene (ABS) chosen in this

work is an interesting, widely used engineering thermo-

plastic owing to its desirable properties which include good

mechanical behavior and chemical resistance.10 There

are still only a few reports about the preparation of ABS/

clay nanocomposites with solution-intercalation techniques.

Pourabas et al. 10 developed a co-solvent method for

the preparation of ABS/clay nanocomposite: the polymer

nanocomposite was precipitated from an ABS-tetrahydro-

furan stirred solution containing organic-modified mon-

tmorillonite by addition of ethanol (precipitating solvent).

The final product exhibited an intercalated structure with a

uniform interlayer spacing of the silicate layers.

In the present work dimethyl-hexadecyl-imidazolium-

modifiedmontmorillonite (DMHDIM–MMT) has been chosen

for the preparation of polymer nanocomposites usingMB and

solution-intercalation techniques. The aim is to investigate the

effectiveness and influence of these two different processes on

dispersion, morphology, and properties of the ABS/clay

nanocomposites, in order to obtain a material that would

combine the excellent mechanical behavior provided by low

amounts of inorganic nanoparticles with the versatility and

easy processing characteristics of rubber-toughened thermo-

plastic.

In our previous work 11 we had studied the effect of the

clay surfactant on the properties of the nanocomposites

prepared by solution-intercalation. The results have con-

firmed the outstanding stability of DMHDIM–MMT as well

as its improved compatibility with ABS matrix with respect

to traditional ammonium salts-based surfactants.

In this work, the morphology, mechanical properties, and

thermal stability of the composites have been assessed by

X-ray diffraction (XRD), transmission electron microscopy

(TEM), dynamic-mechanical analyses (DMA), thermal gravi-

metric analyses (TGA), and by fluorescence spectroscopy

(FS) of optical probes. The last one is an innovative technique

for the rapid evaluation of intercalation and exfoliation in

polymer-clay nanocomposites.12 Preliminary findings are

reported on probe fluorescence in polymer nanocomposites

prepared fromOMLSwith polystyrene (PS) and polyamide 6

(PA6). In particular Nile Blue A has been found to be a

sensitive probe of the local nano-environment and hence a

useful fluorescence probe when co-exchanged into clay with

traditional quaternary ammonium treatments or, high

temperature stable trialkyl-imidazolium based surfac-

tants.13,14

1% (or wt%) is used throughout this manuscript for mass %.

EXPERIMENTAL

Raw materialsThe ABS grade chosen (Magnum 3904, Dow Chemicals) had

a melt-flow index of 4.7 g/10min (2208C/10 kg, UNI-ISO

1133). Dimethyl-hexadecyl-imidazolium/Nile Bluemodified

montmorillonite (DMHDIM–MMT) was prepared by a

standard cationic-exchange procedure.12,13 Sodium mon-

tmorillonite with an ion-exchange capacity of 92meq/100 g


was obtained from Southern Clay Products (Gonzales, Texas)

and exchanged in water/ethanol (1/1 volume ratio) with

1,2-dimethyl-3-hexadecylimidazolium (DMHDIM) bromide

and Nile Blue A Sulfate (Aldrich). The quantities of

DMHDIM and Nile Blue used were equal to 95 and 5% of

the exchange capacity of the layered silicate, respectively; a

20% excess of Nile Blue was used to compensate the presence

of impurities in Nile Blue (assay content about 80%).

DMHDIM was prepared and purified as previously

reported.12,15,16

Preparation of compositesOMLS were dispersed in ABS by ultrasonic solution

blending (US) or MB. US samples were prepared by first

dissolving and stirring ABS in refluxing acetone in a three

neck reflux flask. A dispersion of OMLS in the same solvent

was added to the solution to obtain 5wt%1 concentration of

OMLS in the polymer/clay composite after solvent removal

(ABS/DMHDIM–MMT 5wt%—US). Ultrasonic mixing

(Bransons 1510, maximum power 70W at 72 kHz) was

applied for 6 hr to disperse the OMLS in acetone and the

polymer solution after addition of the OMLS dispersion.

The solvent was then evaporated under vacuum at 508C, andthe composite was dried under vacuum at 1008C for 4 hr to

remove the solvent residue from the solid.

MB composites (ABS/DMHDIM–MMT 5wt%—MB)were

produced by mixing the molten polymer with 5wt% of

OMLS in a 50 cm3 Brabender apparatus working at 1908Cand 4.8 rad/s with a residence time of 5min. The obtained

composites were then compression molded with a Collin

P200 press at 2008C and 30 bar during a 600 sec cycle (with a

cooling rate of 0.58C/sec) to obtain specimens for morpho-

logical and mechanical characterization.

Wide angle X-ray diffraction (WAXD)WAXD patterns were recorded in a 2u angular range of

1.5–408 on a Philips X’Pert PRO diffractometer, working in

reflection geometry and equipped with a graphite mono-

chromator on the diffracted beam (CuKa radiation). The

uncertainty in terms of d-spacings was � 0.05 nm (2s).

Transmission electron microscopy (TEM)TEMmicrographs were acquired with a Philips mod. EM 208

using an acceleration voltage of 100 kV. Specimens were

microtomed using a Leica Ultracut (UCT) after being

embedded in epoxy.

Fluorescence spectroscopy (FS)Fluorescence spectra were obtained using an Ocean Optics

USB2000 spectrometer adapted for fiber optic input with

a 200mm entrance slit width. The light source was a 30W

fluorescent blacklight at 365 nm placed at about 2 cm from

the sample. A bifurcated optical fiber containing seven fibers

of 200mm (core diameter about 1 cm) above and perpen-

dicular to the sample surface was used for collection of


DOI: 10.1002/pat

1578 M. Modesti et al.

fluorescent signal. Integration times were 800ms and 2000ms

for ABS nanocomposites and clay-solvent mixtures, respect-

ively. All measurements were made at room temperature.

Mechanical testingsFlexural modulus and deformation at break were measured

using a universal testingmachine (Galdabini, mod. Sun 2500)

operating with a crosshead speed of 2mm/min and with

specimen dimensions according to UNI ISO 178 (bend test).

Measurements were conducted at room temperature, with

uncertainties of 0.1N and 1mm.

Dynamic-mechanical analysis (DMA)Dynamic-mechanical properties of the samples were

measured using DMA 2980 (TA Instruments). Analyses

were performed using a single-cantilever configuration

between �1008C and þ1008C with a heating rate of 58C/min, frequency of 1Hz, and amplitude of 15mm. Glass

transition temperatures were evaluated from the peaks of

loss modulus function with an uncertainty of 1.58C (2s), as

determined by running a polystyrene standard sample five

times. The maximum standard deviation calculated on

experimental data (Fig. 7) is about �0.5% for loss modulus

peak temperature and �2.5% for storage modulus evaluated

at 258C.

Thermal gravimetric analysis (TGA)The thermal stability of the ABSmatrix and the polymer-clay

composites were studied on a TA Instruments Q5000

analyzer operating from ambient temperature to 8008Cat a heating rate of 208C/min under nitrogen and air

atmospheres. An uncertainty of 0.1wt% (2s) was determined

Figure 1. WAXD patterns for ABS/DMHDIM–M

blending (MB) and ultrasonic solution blending


by running five replicates of a standard calcium oxalate

sample.

Confocal microscopyA laser scanning confocal microscope (LSM510 Carl Zeiss

Inc.) was used to image the samples. The samples were

hot-pressed prior to analysis. A blue laser (l¼ 488 nm) was

used as the coherent light and images were taken with a

505 nm high-band-pass filter at 20� magnification (scan size

461� 461mm). For each sample, 60 single images were taken

bymoving the focal plane (200 nm thick) and were combined

by overlapping, to build up a two-dimensional intensity

projection.

RESULTS AND DISCUSSION

WAXD patterns of the composites and the imidazolium clay

are shown in Fig. 1. The OMLS has a d-spacing of 1.7 nm. By

WAXS the structure of the materials produced by solution-

sonication seems to be very similar to that of the analogous

materials produced by melt-compounding; an intense

reflection peak related to a d-spacing of 2.9 nm is present

in the composite’s spectra, suggesting the formation of

intercalated nanocomposites independent of the processing

conditions. Up to three orders of basal reflections can be

detected, indicating the presence of ordered systems of

stacked clay layers. However, X-ray diffraction is not a

reliable method for estimating the extent of exfoliation and

the presence of intercalated tactoids does not exclude

exfoliation.17

Representative TEM micrographs in Fig. 2 show that both

samples have a mixed intercalated/exfoliated morphology.

At low magnification (Fig. 2a and b), the sample ABS/

MT 5wt% composites obtained with melt-

(US). Solid line indicates pristine OMLS.


DOI: 10.1002/pat

Figure 2. TEM micrographs for ABS/DMHDIM–MMT 5wt% composites obtained

with melt-blending (a, c) and ultrasonic solution blending (b, d) at different mag-

nifications.

Figure 3. Fluorescence spectra for ABS/DMHDIM–NB–

MMT 5wt% composites obtained with melt-blending (MB)

and ultrasonic solution blending (US). Solid line indicates

pristine OMLS.


DMHDIM–MMT 5wt%–MB shows tactoids containing a

larger number of lamellae and, at high magnification

(Fig. 2c and d), clay layers with higher planar dimension.

This suggests that ultrasonication, as compared to MB,

promotes not only a higher extent of exfoliation but also a

more severe reduction in the size of clay platelets due to

fragile fracture.5,6 The previous considerations are deduced

from a limited number of TEM micrographs, where only a

minuscule volume is illuminated, and therefore, it is not

assured that this description represents the bulk of the

samples’ morphology.

Spectroscopy data (Fig. 3) reveal the presence of fluor-

escence (denoted by an intense peak at 610 nm and a weak

one at 480 nm) in the nanocomposites, but no fluorescence in

the OMLS itself due to quenching effects between the dye

molecules.18 Fluorescence has been used for monitoring the

intercalation/exfoliation of the clay.12 It has been shown that

for PA6/DMHDIM–MMT/Nile Blue nanocomposites, the

spectroscopic emission at about 560 nm can be related to

intercalation, while fluorescence effects at 610 nm are

indicative of mixed intercalation/exfoliation structures.

The nature of the emission around 495–500nm is less clear

and could be explained with the desorption of Nile Blue into

the polymer matrix or with the presence of unquenched

higher order aggregates on the clay.12 Emission wavelengths

depend on the nano-confinement of the optical probe and on

the polar character of local environment; thus, fluorescence

spectra can also be used to investigate the preferential

localization of clay in one of the phases composing the

polymer structure (i.e. styrene-acrylonitrile and butadiene).


Modified dyed clay has been dispersed in three different

solvents at a concentration of 5wt%. Each solvent is chosen to

mimic the polarity of a different ABS phase: heptane for

butadiene, acetonitrile for acrylonitrile, and toluene for

styrene. In Fig. 4 the fluorescence spectra for the composite

and the clay in the solvents are shown. The fluorescent

spectra for the ABS/OMLS composites reveal two peaks at


DOI: 10.1002/pat

Figure 4. Fluorescence spectra for ABS/DMHDIM–NB–

MMT 5wt% composite obtained with solution-intercalation

and for OMLS solutions using representative solvents.


about 600 and 480 nm (Fig. 3) which appear to be the

combination of the peaks obtained with toluene and

acetonitrile: this observation suggests that clay resides in

the styrene-acrylonitrile (SAN) rigid phase, as previously

observed by Stretz et al. 19

Images collected by confocal microscope (Fig. 5) show

dark areas due to quenching generated by micrometer

aggregates of clay tactoids. The clay will not fluoresce until

the effective distance between fluorophores is at least 3–5 nm.12 The dyed molecules in the intercalated tactoids are most

likely quenched because, as shown by the XRD, the

d-spacing is about 2.9 nm; thus, we assume that the

fluorescence in the sample is mostly generated by dyed

molecules on the external surface of well dispersed clay

tactoids, or on exfoliated layers.

In the composite images (Fig. 5) (generated by super-

imposing 20 individual confocal images) aggregates of

intercalated tactoids with a maximum dimension of about

50mm are observed for the MB sample, these aggregates are

Figure 5. Composite images from the con

NB–MMT 5wt% composites produced by

solution blending. This figure is available

wiley.com/journal/pat


much smaller in the US composites. This result further

supports a more homogeneous dispersion for US sample as

observed on the mesoscale and is consistent with the

indications discussed above from the TEM data (on the

nanoscale). Thus, the combination of the confocal micro-

scopy, XRD, and TEM data indicate that OMLS has a mixed

intercalated/exfoliated structure and a non-homogeneous

dispersion with the MB samples exhibiting greater hetero-

geneity.

The dispersion differences between the composites

obtained with the two processing conditions are confirmed

by mechanical testings results (Fig. 6). An increase of about

30% in flexural modulus, from about 1.5GPa (pristine

polymer) to about 2.0GPa, has been measured for ABS/

DMHDIM–US composite. This is an indication of the

reinforcing effect exerted by the filler particles, limiting

the mobility of the macromolecules. The smaller increase in

flexural modulus for the MB composite (1850GPa, 17%

increase) suggests a superior dispersion in the US sample as

compared to the MB sample because, as is well known, the

elastic modulus is strongly influenced by the actual degree of

dispersion achieved in the nanocomposite.19

A strong reduction of deformation at break (about 75%)

has been measured for all the composites, which might

suggest that the clay aggregates are acting as micro-sized

defects in the composites that initiate the crack propagation.

The materials were also compared using DMA (Fig. 7). The

storage modulus (E’) increases in all nanocomposites as

compared to the neat polymer, over the entire temperature

range. Again, as already evidenced by mechanical testings,

the reinforcing effect is influenced by the filler dispersion: a

34% and 17% increase in E’ at 258C as compared to the

neat polymer (E’¼ 1690MPa) is observed for ABS/

DMHDIM–US (E’¼ 2280MPa) and ABS/DMHDIM–MB

(E’¼ 1990MPa), respectively. The peaks in the loss modulus

plot identify two glass transition temperatures (Fig. 7): a

lower one, typical of the butadiene rubbery phase

(Tg1��908C) and the higher (Tg2� 1108C), typical of the

rigid SAN phase. These parameters are not affected by the

presence of OMLS, as observed also in previous studies.11,19

focal microscope of: ABS/DMHDIM–

(a) melt-blending and (b) ultrasonic

in colour online at www.interscience.


DOI: 10.1002/pat

Figure 6. Results of flexural strength testing for ABS/

DMHDIM–MMT 5wt% composites obtained with melt-

blending (MB) and ultrasonic solution blending (US). Para-

meters have been normalized with respect to the properties

measured for pure ABS (matrix). Reported uncertainty is

�2s. Uncertainties, calculated for the normalized values,

are obtained combining individual standard uncertainty

according to the law of propagation of uncertainty.


The TGA plots for ABS and polymer/clay composites,

acquired in air and nitrogen at a rate of 208C/min, are shown

in Figs. 8 and 9, respectively. In Fig. 8, two main steps in the

degradation pathway of ABS and its clay composites are

observed. The major mass loss occurs in the first step

between 350 and 4508C: it is attributed to the evolution of

volatiles produced by the decomposition of butadiene

immediately followed by the aromatics of the styrenic

fraction.20 The second step occurs above 4508C, and it is

assigned to the degradation of the carbonaceous products

formed during the first step. No significant increase in

thermal and thermo-oxidative stability is observed for the

nanocomposites as compared to the neat ABS for either

production process. At temperatures higher than 6008C the

experimental residue is equal to the calculated inorganic

Figure 7. Dynamic-mechanical behavior of

obtained with melt-blending (MB) and ultrason


content of the OMLS. In oxidative environments, the onset of

thermal degradation occurs at a slightly lower temperature

in the presence of OMLS. It might be argued that the decrease

in the onset is due to the partial degradation of the clay

surfactant. This phenomenon has been extensively discussed

in a previouswork 11 and it has been shown that themass loss

does not increase proportionally with the OMLS loading

level and, thus, it cannot be due only to the decomposition of

the organic surfactant. Instead, it is believed that OMLS

exerts a catalytic effect on the polymer degradation. Similar

results have been previously reported when the onset of

thermal degradation for the polymer is higher than the onset

of decomposition for the ammonium-based OMLS.11,21

CONCLUSIONS

ABS/clay nanocomposites containing an imidazolium-

salt-modified montmorillonite were prepared by two

different processing methods: the classic melt-intercalation

and a low-temperature solution process. WAXD and TEM

show that with both MB and solution processes, a mixed

intercalated/exfoliated structures is obtained; however,

confocal microscopy, which provides a bulk micrometer

scale characterization, shows that the clay is not homo-

geneously dispersed and that micrometer aggregates of clay

tactoids are present. The sonication process reduces the size

of these aggregates as compared to MB and improves the

degree of dispersion. As expected, the reinforcing action of

the nanofiller in terms of elastic modulus measured by

DMA increases with the extent of dispersion. A strong

reduction in deformation at break has been measured and it

is attributed to the presence of clay aggregates that act as

micro defects in the composites, which may initiate the crack

propagation. Fluorescence spectroscopy suggests the pre-

ferential localization of clay in the rigid SAN phase. No

significant variation in thermal and thermo-oxidative

degradation was observed between the nanocomposites

ABS/DMHDIM–MMT 5wt% composites

ic solution blending (US).


DOI: 10.1002/pat

Figure 8. Thermal stability measurements for pure polymer and ABS/DMHDIM–MMT

5wt% composites obtained with melt-blending (MB) and ultrasonic solution blending

(US) (air—208C/min).

Figure 9. Thermal stability measurements for pure polymer and ABS/DMHDIM–MMT

5wt% composites obtained with melt-blending (MB) and ultrasonic solution blending

(US) (nitrogen—208C/min).


prepared by sonication and MB or between the nanocompo-

sites and the neat polymer. All these data clearly show that,

for the system studied in this work, solution-intercalation is

more effective at dispersing and improving mechanical

properties than MB, and that fluorescence spectroscopy and

confocal microscopy using fluorescence-probe modified clay

are complimentary characterization techniques when used

with WAXS and TEM.

AcknowledgmentsThe authors thank Marcus T. Cicerone, Polymers Division,

NIST, for allowing use of their confocal microscope.


REFERENCES

1. Giannelis EP, Krishnamoorti R, Manias E. Polymer-silicatenanocomposites: model systems for confined polymers andpolymer brushes. Adv. Polym. Sci. 1999; 138: 107–147.

2. Alexandre M, Dubois P. Polymer-layered silicate nanocom-posites: preparation, properties and uses of a new class ofmaterials. Mater. Sci. Eng. 2000; 28: 1–63.

3. Sinha Ray S, Okamoto M. Polymer/layered silicate nano-composites: a review from preparation to processing. Prog.Polym. Sci. 2003; 28: 1539–1641.

4. Ahmadi SJ, Huang YD, Li W. Synthetic routes, propertiesand future applications of polymer-layered silicate nano-composites. J. Mater. Sci. 2004; 39: 1919–1925.

5. Dennis HR, Hunter DL, Chang D, Kim S, White S, White JL,Cho JW, Paul DR. Effect of melt processing conditions on the


DOI: 10.1002/pat


extent of exfoliation in organoclay-based nanocomposites.Polymer 2001; 42: 9513–9522.

6. Yalcin B, CakmakM. The role of plasticizer on the exfoliationand dispersion and fracture behavior of clay particles in PVCmatrix: a comprehensivemorphological study. Polymer 2004;45: 6623–6638.

7. Xie W, Gao Z, Pan WP, Hunter D, Singh A, Vaia S. Thermaldegradation chemistry of alkyl quaternary ammoniummon-tmorillonite. Chem. Mater. 2001; 13: 2979–2990.

8. Hartwig A, Putz D, Schartel B, Bartholmai M, Wendschuh-Josties M. Combustion behaviour of epoxide based nano-composites with ammonium and phosphonium bentonites.Macrom. Chem. Phys. 2003; 204: 2247–2257.

9. Awad WH, Gilman JW, Nyden M, Harris RH Jr, Sutto TE,Callahan J, Trulove PC, DeLong HC, Fox DM. Thermaldegradation studies of alkyl-imidazolium salts and theirapplication in nanocomposites. Thermochim. Acta 2004;409: 3–11.

10. Pourabas B, Raeesi V. Preparation of ABS/montmorillonitenanocomposite using a solvent/non-solvent method. Poly-mer 2005; 46: 5533–5540.

11. Modesti M, Besco S, Lorenzetti A, Causin V, Marega C,Gilman JW, Fox DM, Trulove PC, DeLong HC, ZammaranoM. ABS/clay nanocomposites obtained by solution tech-nique: influence of clays’ organic modifiers. Pol. Deg. Stab.2007; 92: 2206–2213.

12. Maupin PH, Gilman JW, Harris RH Jr, Bellayer S, Bur AJ,Roth SC, Murariu M, Morgan AB, Harris JD. Optical probesfor monitoring intercalation and exfoliation in melt-processed polymer nanocomposites. Macromol. RapidCommun. 2004; 25: 788–792.

13. Gilman JW, Awad WH, Davis RD, Shields J, Kashiwagi T,VanderHart DL, Harris RH Jr, Davis C, Morgan AB, Sutto


TE, Callahan J, Truelove PC, Delong HC. Polymer/layeredsilicate nanocomposites from thermally stable trialkylimi-dazolium-treated montmorillonite. Chem. Mater. 2002; 14:3776–3785.

14. Bottino FA, Fabbri E, Fragala LI, Malandrino G, Orestano A,Pilati F, Pollicino A. Polystyrene-clay nanocomposites pre-pared with polymerizable imidazolium surfactants. Macro-mol. Rapid Commun. 2003; 24: 1079–1084.

15. Vaia RA, Teukolsky RK, Giannelis EP. Interlayer structureand molecular environment of alkylammonium layeredsilicates. Chem. Mater. 1994; 6: 1017–1022.

16. Zhong-Zhen Y, Mingshu Y, Qingxin Z, Chungui Z,Yiu-Wing M. Dispersion and distribution of organicallymodified montmorillonite in nylon-66 matrix. J. Polym.Sci. Part B, Polym Phys. 2003; 41: 1234–1243.

17. Vaia RA, Liu W. X-ray powder diffraction of polymer/layered silicate nanocomposites: model and practice.J. Polym. Sci. Part B, Polym Phys. 2002; 40: 1590–1600.

18. Baumann R, Ferrante C, Deeg FW, Brauchle C. Solvationdynamics of nile blue in ethanol confined in porous sol–gelglasses. J. Chem. Phys. 2001; 114: 5781–5791.

19. Stretz HA, Paul DR, Cassidy PE. poly(styrene-co-acryloni-trile)/montmorillonite organoclay mixtures: amodelsystem for ABS nanocomposites. Polymer 2005; 46: 3818–3830.

20. Shaofeng W, Yuan H, Lei S, Zhengzhou W, Zuyao C,Weicheng F. Preparation and thermal properties of ABS/montmorillonite nanocomposite. Pol. Deg. Stab. 2002; 77:423–426.

21. Zammarano M. Thermoset fire retardant nanocomposites.In Morgan A, Wilkie CA (eds), Flame Retardant PolymerNanocomposites, Morgan A, Wilkie CA (eds). John Wiley &Sons, Inc.: Hoboken, New Jersey, 2007; 235–284.


DOI: 10.1002/pat

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