Chemical Reactions Involving Viscosity Changes

By Madhura Deval

Introduction

This report discusses reactions and processes during which a change in viscosity is observed.

These reactions have been classified into six categories : Redox Reactions, Photoisomerisation,

pH dependent viscosity (i.e. neutralization), Saponification, polymerization and gelation. The

experimental conditions required and the apparatus used to carry out these reactions have been

described in detail for most reactions. The viscosity of the reactant mixture initially and at the

end of the reaction is also provided wherever possible. The reason behind the change in viscosity

has been discussed for some reactions.

I) Redox reactions –

A new type of Electrorheological fluid called FTMA has been developed. FTMA is a cationic

switchable ferrocenyl surfactant. The degree of entanglement of worm like micelles formed by

FTMA in the presence of Sodium silicates can be manipulated using redox reactions. The degree

of entanglement largely affects the viscoelastic properties of the fluid, hence the viscoelasticity

of the fluid changes during redox reactions (K. Tsuchia et al. , 2004).

The FTMA/NaSal solution was prepared using distilled water (N2 had been bubbled through the

distilled water for 30 minutes to create a nitrogen environment). Stock solutions were

prepared for both FTMA and NaSol, these solutions were gently vortex mixed together to obtain

the aqueous FTMA/NaSal solution. The solution was equilibrated using a thermostatic bath at

25o C. (K. Tsuchia et al. , 2004).

The electrolysis was carried out at 25oC using a three electrode system. A saturated calomel

electrode was used as a reference electrode. A platinum plate and a platinum wire were used as

working and auxiliary electrodes respectively. Aqueous NaSal solution was used as the

supporting electrolyte. Electrolytic oxidation was performed on the reduced aqueous mixture

using a potentiometer to maintain a +0.5V vs. SCE for 24hrs (the solution was bubbled with N2

and stirred continuously). The reduction reaction taking place at the auxiliary electrode was the

reduction of water. (K. Tsuchia et al. , 2004).

2

Figure 1 Oxidized FTMA/NaSal (top) reduced FTMA/NaSal(bottom) (K. Tsuchia et al. , 2004).

The rheology of the reduced and oxidized FTMA/NaSal solution was characterized using a cone

and plate type geometry and a double concentric cylinder type rheometer respectively. The

oxidized sample showed Newtonian behavior while the reduced sample showed non-Newtonian

behavior. The reduced sample had a zero-shear viscosity of 15Pas and the oxidized sample had a

viscosity of 2.5x10-3Pas. The viscosity of the solution reduces by a factor of 6000 over the course

of the reaction. (K. Tsuchia et al. , 2004).

II) Photoisomerisation –

AZTMA is a photo-switchable surfactant which exhibits reversible cis-trans photoisomerization.

A reactants system consisting of Cetyltrimethylammonium bromide (CTAB), trans-AZTMA and

NaSal undergoes a viscosity decrease when irradiated with a UV light. When irradiated with UV

light, trans-AZTMA undergoes isomerisation and changes to cis-AZTMA. This change in

viscosity probably occurs because of the difference in structure and geometric properties of cis-

AZTMA and trans-AZTMA. As seen from the diagram cis-AZTMA is bulky while trans-

AZTMA is more or less linear. When NaSal is added to an aqueous solution of CTAB, the

CTAB forms worm like micelles. trans-AZTMA align itself in a manner which preserves the

worm-like aggregate formed but cis-AZTMA probably breaks the worm-like micelles into

smaller rod shaped aggregates which reduces the viscosity of the reactant system.

Figure 2 Structure of cis –AZTMA (bottom) and trans-AZTMA(top) (Sakai et al. , 2005)

3

This change in aggregation state is reversible; the cis-AZTMA can be converted back to trans-

AZTMA by irradiating the reactant mixture with light in the visible range. This causes the

viscosity of the solution to increase. (Sakai et al. , 2005).

This process was carried out in a quartz cuvette. The source of radiation was a Hg-Xe lamp. The

reactant solution was prepared by mixing 10mM of trans-AZTMA with 50mM of aqueous

CTAB, 50mM of NaSal solution was added to this mixture. The sample must be irradiated for at

least 120 minutes in order for it to have achieved a photo-stationary state. The viscosity of the

solution decreased from 100Pas to 0.1Pas. The zero shear viscosity of the solution decreased by

four orders of magnitude over the timescale of the reaction. (Sakai et al. , 2005).

III) pH and viscosity –

The viscosity of aqueous solutions of certain polymers depends on the pH of those solutions and

can be increased or decreased by changing the pH. (Nagatsu et al. , 2007).

This fact has been used by Nagatsu et al. in studying miscible viscous fingering where the

displaced and displacing phases react with each other. The polymer used by them was

Polyacrylic Acid (PAA). The disassociation equilibrium equation of PAA in water is given by :

The viscosity of this solution is higher when the forward direction is favored i.e. the

concentration of Carboxylate ions is higher compared to the concentration of Carboxyl group.

The electrostatic repulsion between Carboxylate ions causes the polymer chain to expand which

increases the viscosity of the solution. Therefore an increase in pH would cause the reaction to

proceed in the forward direction and increase the viscosity of the solution, while decreasing the

pH would favor the reverse direction and the viscosity of the solution would decrease. The

viscosity of the solution can be manipulated by adding aqueous solutions of NaOH or HCl to it.

The viscosity of a 0.5wt% solution of PAA (Molecular weight = 1 million) increases with the

concentration of NaOH solution until the concentration reaches a value of 0.065mol -1 . Above

this value the NaOH is present in excess and the Na+ ions reduce the electrostatic repulsion

between the Carboxylate ions, this decreases the viscosity of the solution. Adding HCl to a

4

solution containing 0.5wt% PAA with NaOH (0.065mol-1) decreases the viscosity of the

solution. This increase and decrease in viscosity are observed at all values of shear rate. The

Ostwald De Waele power law model for viscosity can be used to describe the relationship

between viscosity () and Shear rate (γ¿

) :

= k n-1

Here the value n at different concentrations of NaOH and HCl in the solution (i.e. at different

pH) is almost the same,(approximately 0.59) therefore at a constant shear rate the value of

viscosity will be proportional to k . The elastic properties of this solution can be neglected below

a fixed value of the shear rate. (for the 0.5wt% PAA solution this value is 1000s-1). (Nagatsu et

al. , 2007).

Figure 3 The plot of K(which is proportional to viscosity) vs pH at constant shear rate. (Nagatsu et al. , 2009)

The Damkohler (Da) number is a dimensionless quantity used to compare the rate of fluid

motion to the rate of the reaction. It is defined as the ratio of Characteristic time of fluid motion

to the characteristic time of the reaction. A Da of zero indicates no reaction while a Da of infinity

indicates instantaneous reaction. For the neutralization reaction described above the value of Da

is infinity. (Nagatsu et al. , 2009).

Chemical reaction between a solution containing Polyethylene Oxide (PEO) and an aqueous

5

solution containing copper and ferrous ions is known to cause a viscosity decrease. This reaction

has a finite value of Da. (Nagatsu et al. , 2009).

The change in viscosity observed during this reaction was quantified by measuring the torque

required by an impeller to agitate the reaction mixture at a constant rate of 100rpm. The reaction

was carried out in a cylindrical acrylic vessel (inner diameter = 130mm). A six blade impeller

(diameter = 100mm;height = 60mm) was used to agitate the solution. The solution containing

Cu2+ and Fe2+ ions was added to the reaction vessel over a period of 40s using a roller pump. The

torque was measured using a torque meter. (Nagatsu et al. , 2009).

The reactant mixture shows a decrease in torque/viscosity over the course of the reaction. The

reaction can be considered to have reached completion when the torque/viscosity reaches a

constant value. The rate at which the torque reaches this constant value indicates the rate of the

reaction. Reactant solutions containing a higher concentration of ions tend to reach constant

torque faster than ones containing fewer ions. (Nagatsu et al. , 2009).

The of PEO (molecular weight = 5million) solution used for this study shows shear thinning

behavior, its elastic properties can be neglected as long as the shear strain stays under 100s -1 (for

1wt% solution). The final viscosity of the solution i.e. the viscosity after the addition of the

aqueous ionic solution is equal to the viscosity of water. (Nagatsu et al. , 2009).

The viscosity of an aqueous solution of modified Acryl Amide (AM) and Acrylic Acid (AA)

terpolymers can be altered by changing the pH of the solution. Research related to this has been

carried out by Yan Li and Jan C. T. Kwak (2002). The copolymer has been prepared using a free

radical polymerization method described by J. Effing. The pH of the solution was controlled by

titration with aqueous NaOH solution. Different terpolymers were prepared by varying the

amounts of AA, AM and the type of hydrophobic monomer used (n-dodecylacrylamide or n-

tetradecylacrylamide) .

Viscosity of the solutions was measured using a coaxial cylinder system at a temperature of 23oC

at a constant shear rate of 9.36 s-1. An increase in viscosity was observed at intermediate pH

levels (3.5 - 4.8) for all polymers. The degree of change in viscosity was found to depend on the

amount of AA group in the polymer and the hydrophobic component of the polymer. The largest

changes were observed for polymers with 40% AA and n-tetradecylacrylamide hydrophobic

monomer. For pH values between 3.5- 4 (which corresponds to 25% neutralization), Acrylic Acid

groups get partially ionized. These partially ionized groups repel each other and cause the

6

entangled polymer chains to expand. This expansion facilitates interpolymer Hydrogen bonding

and hydrophobic interactions which are responsible for the large viscosity increase. The viscosity

reaches a maximum value at pH≈4.8. Beyond pH≈4.8 the repulsion between the partially

ionized groups exceeds the attractive hydrophobic interactions causing the viscosity of the

solution to decrease. At pH≈7 the viscosity reaches a constant value which is slightly higher than

the initial viscosity. If the length of the Hydrophobic group used in producing the polymer is

large enough a gel-like system can be obtained at a pH of 7. (Yan Li & Jan C. T. Kwak , 2002)

The pH of dispersions of Titanium dioxide nanoparticles with certain acids are sensitive to pH.

The viscosities of dispersion are determined by the strength of the intermolecular interactions.

The intermolecular interactions that should be considered here are the van der waals forces

(attractive), electric double layer interactions(repulsive) and bridging (attractive) . These

interactions are affected by adsorption of molecules on to the surface of TiO2 particles. These

dispersions were prepared using aqueous grinding. TiO2 and monocarboxylic acids (benzoic ,

salicylic)/dicarboxylic acids( isophthalic , terephthalic and pyridine-2,5-dicarboxylic acid ) were

added to a ceramic jar along with water and different amounts of 1M HCl or NaOH (varying

quantity of these corresponds to changing the pH). Twenty ceramic beads were added to the jar;

it was sealed and rotated at 85rpm for 18 hours. (Johnson et al. , 2007).

The viscosity of the dispersions was higher for dispersions in dicarboxylic acids than

monocarboxylic acids under acidic conditions (pH ≈ 3). Viscosity appears to reach a constant

value at pH ≈ 5 for all acids. In this experiment HCl was used to decrease the pH and NaOH was

used to increase it. Adding HCl caused a larger change in pH than adding NaOH . Dicarboxylic

acid dispersions have a higher average viscosity than mono carboxylic acids this is due to the

bifunctional nature of the molecules of the acid. These acids contain two COOH groups , both of

which can adsorb onto the surface of the TiO2 particles and act as a bridge. This increases the

strength of the attractive intermolecular interactions between the two particles and in turn

increases the viscosity of the fluid. Therefore dicarboxylic acids have a higher initial viscosity

than monocarboxylic acids but the final viscosities of both acids are around the same value

(4.5x103cP approx. ). The largest change observed was for in Salicylic acid the viscosity

increased by a factor of 300. (Johnson et al. , 2007)

Acid Catalyzed autocatalytic reactions of polyelectrolytes have been carried out in Hele Shaw

cells in order to study density fingering. This viscosity and density of the reaction mixture

7

changes over the course of the reaction . The reactant solution consisted of K 2S4O6, NaClO2,

NaOH, Bromophenol blue (indicator), Polyacrylamide, Polyelectrolyte and hence [COO-] in

different concentrations. Once the reactant solution was placed in the Hele Shaw cell the reaction

was initiated by applying a potential difference of 2.8 V across a Platinum wire electrode and a

copper wire electrode for 9-20s. As the reaction proceeded the color of the indicator underwent

a color change from blue to bright yellow indicating a decrease in pH. (Rica et. al. 2008)

The viscosity of the solution (relative to viscosity of water) became almost 1/5 th of its initial

viscosity over the course of the reaction. This decrease has been attributed to the drop in pH

which in turn was caused by the increasing ionic strength of the solution. The density of the

reactant mixture also changes. The change in density depends on the concentration of reactants

and can be around 3x10-4g/cm3. (Rica et. al. 2008)

IV) Saponification –

Saponification reaction is the hydrolysis of fatty acids/oils (esters) by a base. The general

reaction is as follows :

Fat + Metal Hydroxide Glycerol + organic acid salt

(organic acid/oil) (Sodium Hydroxide (Soap)

is used most often)

This reaction is used in the soap manufacture.

The viscosity change accompanying this type of reaction has been studied by Morgunov and

Perchenko (1976). The reaction examined by them was between oxidised paraffin and NaOH

solution. The liquid oxidised paraffin used was obtained through liquid phase catalytic oxidation

of petroleum paraffin by oxygen. The reaction was carried out in a 500ml stainless steel reactor

with a high speed propeller stirrer and a water cooled reflux condenser. The aqueous NaOH

solution has a concentration of about 28% by weight. The temperature of the reactor was kept

constant within ±0.2oC. A sharp increase in viscosity was observed at about 60% saponification

and which continued until about 89% saponification. The viscosity increases by a factor of 15.

Gelation can occur if the concentrations of fatty acids is in the range of (1.1-1.2)mol/L and the

water concentration is below (6-8) mol/L.

Another study based on the viscosity changes during a saponification reaction involves the

8

saponification of Poly Vinyl Pivalate (PVPi) by NaOH solution to produce Poly Vinyl Alcohol

(PVA). The PVPi used for this process must have high stereoregularity and can be synthesised by

the bulk polymerisation (initiated using UV rays) of Vinyl Pivalate. An NaOH solution was

added drop by drop to a solution of PVPi in tetrahydrofuran. The solution was stirred using a H –

shaped anchor type stirrer at 20000rpm. The reaction was carried out at 60oC. (Lyoo et. al., 2001)

Shear viscosity measurements were made over the course of the reaction the shear rate was kept

at a constant value of 50s-1. Initially the viscosity of the reaction mixture decreased from a value

of 5x103Pas to approximately 3.5x103Pas. This was due to the mixing of all the reactants

together. After the initial decrease the viscosity, it increased to a maximum value of 5.5x103Pas.

Rod climbing was observed at this value. As the reaction proceeded the viscosity of the gel

continued to decrease, at 99.9% saponification the viscosity of the reaction reached a value of

6x102Pas. The decrease in viscosity is caused by fibril formation. The reaction takes about 16.67

minutes to reach completion. (Lyoo et. al. 2001)

A saponification reaction has been carried out in a Hele Shaw cell by Fernandez & Homsy

(2003). An aqueous solution of NaOH was injected in a Hele Shaw cell already filled with

Linoleic acid dissolved in mineral oil. Saponification takes place at the oil/water interface and a

soap is formed. The purpose of this study was to study the effects of insitu surfactant production

(which alters surface tension at the interface) on viscous fingering hence data related to viscosity

was not reported.

V) Polymerization –

Monomer conversion during polymerization reactions is often accompanied with a large increase

in viscosity. The increase in viscosity is larger during homogeneous polymerization processes

like bulk and solution polymerization than the increase during non-homogeneous processes like

emulsion and suspension polymerization. The viscosity () of a polymer melt can be given by :

¿ K M wα

Where K depends on the polymer/polymer solution and M is the Molar mass of the polymer. The

value of depends on the Molar mass of the polymer. This is the starting equation used to build

models relating viscosity to reaction kinetics. (Moritz ,1989)

9

Figure 4 viscosity changes for different types of polymerization (Moritz ,1989)

A large change in viscosity occurs during the isothermal network polymerization of

polyurethane. The reactant system consists of Є -caprolactone containing 99% primary Hydroxyl

group and 4-4’, diphenyl methane diisocyanate containing 98.9% active isocyanate groups. The

system is catalysed using (0.0111±2.5%) moles/m3 dibutyl tin dilaurate. These reactants most be

metered and then mixed together in an impingement mixer. After the mixing process is complete

the mixture should be injected into an insulated cup and then transferred to a cone and plate

rhemometric mechanical spectrometer. This entire procedure must be carried out within 20

seconds. (Richter & Macosko ,1980).

The viscosity measurements were made over a temperature range of 323K-363K. The reactant

mixture does not show shear thinning behaviour. The viscosity measurements show that a

gelation occurs at about 0.707 minutes. The viscosity of the reactant mixture increases by five

orders of magnitude in 8.5 minutes - 41 minutes approximately depending on the temperature of

the reactant mixture .The results obtained from these measurements show that the network

formation is idea and free of any side reactions. The change in viscosity for different

temperatures is shown in figure 5 (Richter & Macosko ,1980).

An example of a condensation reaction in which the viscosity of the reactant mixture increases is

the reaction between Urea and Formaldehyde. This reaction can be catalyzed using an acid This

reaction was carried out by combining formalin (39.37% concentration, 3.12% methanol,

180ppm acidity and a pH of 5.1 which was maintained using 0.1M NaOH) with Urea in the

10

ratio 1.94. The reactant solution was stirred for 4 minutes , the pH of the solution was changed to

8.5. The reaction was initiated about 35 minutes after stirring. The temperature is kept constant

85oC ± 1oC. The viscosity of the reaction mixture at depends on the pH at which the reaction is

carried out. (Mehdiabadi et. al., 1998)

The kinematic viscosity was measured over the course of the reaction. The viscosity

measurements are made at a temperature of 25oC. The Kinematic viscosity of the reactant

mixture followed the following model :

� ln(ν /9.43)=(0.001586 /1337.938∗10−pH)∗t

This model works only for the specific experimental conditions described here. (Mehdiabadi et.

al., 1998)

Figure 5 Increase in viscosity during polymerization of polyurethane at different temperatures (Richter & Macosko ,1980).

11

VI) Gelation –

Gelation is the process by which a three dimensional network is formed. This process of network

formation leads to the production of a substance with a high viscosity.

The hydrolysis of Gelatin solutions by enzymes or acids causes a decrease in viscosity of the

solution (20%-30% decrease from initial value). A possible reason for this decrease in viscosity

is the presence of insoluble micelles like particles in the gelatine solution. In a gelatin solution

where the overall concentration of gelatine is less than 10% , the concentration of soluble

components of gelatine is higher inside the micelles rather than outside. Addition of an acid or

alkali causes the micelles to swell (due to the existence Donnan equilibrium). When the acid or

enzyme hydrolyses the swollen micelle network or the soluble components of the solution, it

causes the swollen micelles to rupture, this decreases the volume of the solution and hence its

viscosity is also reduced. (Northrop ,1929)

The gelatin solution used in this study was prepared by the method described by Northrop, J. H.

and Kunitz M.. The decrease in viscosity at different pH values and as a function of increase

formol titration was examined. The decrease in viscosity of both 8% and 1% gelatin solutions

has been examined The largest decrease was observed for the 8% solution of gelatin. The

viscosity of the reactant mixture decreased from 13 to 4.5 , therefore reduced by a factor of 2.89.

The temperature was kept constant at 37oC. (Northrop ,1929)

The formation of a gel in the context of viscous fingering has been examined by Nagatsu et al.

The reaction examined was between an aqueous solution of Sodium polyacrylate (SPA) and Fe3+

ions. The reaction was initiated by adding aqueous Fe(NO3)3 to a beaker containing 30ml of

0.625wt% SPA solution. The Fe(NO3)3 was added at a rate of 1ml/s for a period of 10 seconds.

The two solutions were stirred at a constant rate by a magnetic stirrer. Three different

concentration of Fe3+ ions were tested 0.01M, 0.1M and 1.2M. The reaction vessel . For the first

two cases the yellow gel like mass can be seen inside the beaker. For the last case i.e.

concentration of Fe3+ ions at 1.2M a clear separation can be observed. The sol containing Fe3+

ions stays on top while the SPA solution remains at the bottom. This happens because at this

concentration of Fe3+ ions a gel like substance forms a film at the interface between the two

liquids. This substance is hard enough to support the solution containing Fe3+ ions. The gel

formed could not be removed from the beaker because of its soft and delicate texture, hence

12

rheological measurements could not be made. (Nagatsu et al. , 2008).

Figure 6 Reaction with: (a) 0.01M Fe3+ ions, (b) 0.1M Fe3+ ions and (c) 1.2M Fe3+ ions (Nagatsu et al. , 2008)

The addition of salt to a Polycarboxylate induces physical gelation. The polycarboxylate used in

this study was a polyactone (reduced PLAC) . This polymer is hydrophilic. Different samples

were prepared by varying the compositions of Allyl alcohol, hemiacetal component and COOH

group in the polymer. These were prepared using either of the two methods described below :

1. A solution of red-PLAC in DMSO or DMF/MeOH was slowly added to Methanol

dissolved in NaBH4, the reaction mixture was stirred for 5hrs and the temperature was

maintained at 0oC. This procedure produces a polymer rich in hemiacetal component.

2. The second method involves further processing the red-PLAC produced by the first

method. The red-PLAC is stirred for an additional 5hrs at a temperature of 25 oC. This

procedure converts some of the existing hemiacetal groups to Allyl group while keeping

the Carboxyl group component constant. (Kabuto,2008)

The viscosity of red-PLAC solution is said to increase or decrease when metal salts (e.g. NaCl,

LiCl etc) are added to it. This salt induced thinning or thickening is followed by gelation. The

viscosity of solutions containing up to 40% Carboxyl group was measured at various

concentration of NaCl. These measurements were made at 6oC using a vibration type viscometer.

The viscosity of the samples decreased upon the initial addition of NaCl but started to increase

when the concentration was in the range of (0.025-0.05) mol NaCl/kg. This occurred for all the

samples except for the one with a relatively high Allyl alcohol content (43%) and a relatively low

hemiacetal content (20%). The largest increase in viscosity was observed for the polymer

containing 34% COOH group, 49% hemiacetal component and 12% allyl alcohol. It was

prepared using procedure 1. The viscosity of the solution increases from 40mPas to 60mPas

when the concentration of NaCl is increased. The solution reaches the gel point at a critical value

of concentration, i.e. above this value the solution attains a gel like texture. (Kabuto,2008)

The viscosity of the polymer at concentrations of 0.08M NaCl was measured at different

temperatures. A steady decrease in viscosity is observed until 25oC. If the temperature is then

13

decreased from 25oC to 23oC, gelation is observed. The gel formation is hypothesised to be a

result of exothermic interactions between the polymer molecules. (Kabuto,2008)

The reason for the viscosity increase of the polymer solution on the addition of salt is the

formation of Hydrogen bonds between polymer molecules due to the presence of hemiacetal OH

group. The Hydrogen bond formed between COOH groups and the hemiacetal OH group does

not play a significant role in this type of gelation. (Kabuto,2008)

Table 1 Summary of Properties of reactants and products in Various reactions *

Reaction Brief Description of Reaction and Properties of

reactants/products

Viscosity

Change

Redox Reduced FTMA/NaSal solution (zero-shear viscosity =

15Pas) is oxidized, the viscosity of the oxidized sample =

2.5x10-3Pas.

Decreases by

a factor of

6000

Photoisomerization trans- AZTMA in NaSal and CTAB (zero-shear viscosity =

100Pas) changes to cis- AZTMA in NaSal and CTAB (zero-

shear viscosity = 0.1Pas)

Decreases by

four orders of

magnitude

pH and viscosity PAA(0.5wt%) (viscosity = 1.5x103mPas) reacts with NaOH

(0.065mol/L) to produce SPA (viscosity = 6.3x103mPas)

Increases by a

factor of 4.2

approximately

Terpolymer made from 40% AA and n-

tetradecylacrylamide with NaOH solution.

Maximum viscosity = 30Pas at pH = 4.75

Shear rate = 9.36s-1

Refer to

Figure 7

Dispersions of Titanium dioxide nanoparticles in Salicylic

acid with either HCl or NaOH .

Minimum viscosity = 14cP at pH = 3; Maximum viscosity =

4.5x103cP at pH= 9

Increases by a

factor of 300

K2S4O6, NaClO2, NaOH, Bromophenol blue (indicator),

Polyacrylamide, Polyelectrolyte and hence [COO-] viscosity

relative to water = 40 at ionic strength = 0Mol/dm3;viscosity

Decreases by

a factor of 5.

Density:

* All measurements are at 25oC with a few exceptions

14

relative to water = 7.5 at ionic strength = 0.1Mol/dm3 decreases by

3x10-4g/cm3

Saponification Oxidised Paraffin Wax reacting with NaOH (at temp

=100oC)

Kinematic Viscosity = 10-5cSt at Degree of Saponification

(DS) = 0%; Kinematic viscosity = 1.5x10-4cSt at DS= 90%

Increases by a

factor of 15

Poly Vinyl Pivalate (PVPi) reacted with NaOH solution(at

temp.=60oC) to produce Poly Vinyl Alcohol (PVA)

Maximum Viscosity = 5.5x103Pas ;Minimum Viscosity =

0.75x103Pas at DS= 99.9%

Shear rate = 50s-1

Decreases by

a factor of

7.33

Polymerization Є-caprolactone reacted with 4-4’ diphenyl methane

diisocyanate in the presence of dibutyl tin dilaurate. (at temp

= 70oC) Initial Viscosity = 10-1Pas; Final Viscosity =

8.2x104Pas

Increases 5

orders of

magnitude

Gelation Formol titration of gelatine with NaOH (at temp = 37oC) at

constant pH of = 4.7, Initial viscosity relative to water = 13,

Final viscosity relative to water = 4.5.

Viscosity of water taken to be 1.

Decreases by

a factor of

2.89

red-PLAC solution with NaCl solution

Initial viscosity = 40mPas, Final viscosity = 60mPas

Increases by a

factor of 1.5

Figure 7 The variation of viscosity with pH for AA Terpolymer, largest increase was observed for 40% AA and n-tetradecylacrylamide (Yan Li & Jan C. T. Kwak , 2002)

15

Conclusions

Reactions that give the largest viscosity changes appear to have the most complicates

experimental setups. The redox reaction described here gives the largest increase in viscosity,

but a three electrode system is required to initiate it. One of the cause behind changes in viscosity

during chemical reactions is the difference in geometries of the products and the reactants.

Another reason for a change could be changes in the charge on the reactants over the course of

the reaction. These changes affect the way molecules interact with each other and can cause a

change in viscosity.

16

References

Juan Fernandez and G. M. Homsy (2003). Viscous fingering with chemical reaction:effect of in-

situ production of surfactants. J. Fluid Mech. 480, 267–281.

Abby M. Johnson, Sofia Trakhtenberg, Amy S. Cannon, and John C. Warner (2007). Effect of

pH on the Viscosity of Titanium Dioxide Aqueous Dispersions with Carboxylic Acids. J.

Phys. Chem. A, 111, 8139-8146.

Akio Kabuto , Yuko Sakai , Toru Yahata, Eisuke Okazaki & Mitsuru Satoh (2008). Salt-induced

thickening and gelation of a poly(carboxylate) having three kinds of hydroxyl groups.

Colloid Polym Sci.,286,535–543.

Yan Li and Jan C. T. Kwak (2002). pH-Dependent Viscosity Enhancement in Aqueous Systems

of Hydrophobically Modified Acrylamide and Acrylic Acid Copolymers. Langmuir, 18,

10049-10051.

Won Seok Lyoo, Joon Ho Kim, Jin Hyun Choi, Byoung Chul Kim, John Blackwell (2001). Role

of Degree of Saponification in the Shear-Induced Molecular Orientation of

Syndiotacticity-Rich Ultrahigh Molecular Weight Poly(vinyl alcohol). Macromolecules,

34, 3982-3987.

S. Mehdiabadi, M. S. Nehzat, R. Bagheri (1998). Correlating Viscosity in Urea–Formaldehyde

Polymerization. Journal of Applied Polymer Science, 69, 631–636.

A. N. Morguaov and A. A. Perchenko (1976). Change In Viscosity Of Oxidised Wax Upon

Saponification With Aqueous Sodium Hydroxide Solution. All-Union Scientific-Research

Institute of Surfactants (VNIIPAV)., 1, 20-23.

Hans Ulrich Moritz (1989). Increase in Viscosity and its Influence on Polymerization Processes.

Chem. Eng. Technol., 12, 71 -87.

Yuichiro Nagatsu, Kenji Matsuda,Yoshihito Kato And Yutaka Tada (2007). Experimental study

on miscible viscous fingering involving viscosity changes induced by variations in

chemical species concentrations due to chemical reactions. J. Fluid Mech., 571, 475–493.

Yuichiro Nagatsu, Yusuke Kondo,Yoshihito Kato And Yutaka Tada (2009). Effects of moderate

Damkohler number on miscible viscous fingering involving viscosity decrease due to a

chemical reaction. J. Fluid Mech., 625, 97-124.

17

Yuichiro Nagatsu, Atsushi Hayashi, Mitsumasa Ban, Yoshihito Kato, and Yutaka Tada (2008).

Spiral pattern in a radial displacement involving a reaction-producing gel. Physical

Review E ,78, 026307,1-6

John H. Northrop (1929). Chemical And Physical Changes In Gelatin Solutions During

Hydrolysis. The Journal of General Physiology,529-535

Tama´s Rica, Horvath, and Agota Toth (2008). Dezsö Viscosity-Change-Induced Density

Fingering in Polyelectrolytes. J. Phys. Chem, 112, 14593–14596.

E. B. Richter & C. W. Macosko (1980). Viscosity Changes During Isothermal and Adiabatic

Urethane Network Polymerization. Polymer Engineering And Science, 20(14), 921-924.

Hideki Sakai, Yoichi Orihara, Hideki Kodashima, Atsutoshi Matsumura, Takahiro Ohkubo,

Koji Tsuchiya, and Masahiko Abe (2005). Photoinduced Reversible Change of Fluid

Viscosity. J. AM. CHEM. SOC., 127(39), 13454-13455.

Koji Tsuchiya, Yoichi Orihara, Yukishige Kondo, Norio Yoshino, Takahiro Ohkubo,

Hideki Sakai, and Masahiko Abe (2004). Control of Viscoelasticity Using Redox

Reaction. J. AM. CHEM. SOC., 126(39), 12282-12283.

18