Phase transition in swollen gels. 6. Effect of aging on the extent of hydrolysis of aqueous polyacrylamide solutions and on the collapse of gels

Ilavský, M.; Hrouz, J.; Stejskal, Jaroslav; Bouchal, K.

doi:10.1021/ma00142a072

Cited by 68 publications

(37 citation statements)

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“…This requirement can be met by assuming that the effective degree of ionization is lower than the salt concentration, i.e., IX = 4>x s , where 4> is the correction factor (see footnote* 1). The 4> values thus calculated lie in the range 0.07-0.39 (Table I) and are much lower than those found for P(AAm/sodium methacrylate) hydrogels 1 7 (4) '" 0.96-0.99) and variously aged PAAm networks 33 On the other hand, the values of 4> are comparable with those found for ionic P(AAm/quaternary ammonium salts) hydrogels 34 with 4>",0.1-0.4. From this comparison it seems that it is mainly the low efficiency of ammonium salts, which leads to low 4> values (probably a large size of ammonium group which forms a weaker electrostatic field, due to which the hydration of the group is smaller).…”

Section: Comparison Of the Theory Of Swelling Equilibria Of Polyelectcontrasting

confidence: 53%

Phase Transition in Swollen Gels XXIII. Effect of the Positive Charge Concentration on the Collapse and Mechanical Behavior of Poly(1-vinyl-2-pyrrolidone) Gels

Mamytbekov

Bouchal

Ilavský

et al. 1998

Polym J

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ABSTRACT:The swelling and mechanical behavior of ionized networks of copolymers of 1-vinyl-2-pyrrolidone, ionic comonomer, N,N-dimethyl-N,N-diallylammonium chloride (molar fraction of salt Xs = 0--0.27) and crosslinker, 3,3'-ethylidenebis(l-vinyl-2-pyrrolidone) was investigated in water-acetone mixtures and aqueous NaCl solutions. The networks were prepared by a radiation copolymerization method. At xs2:0.038, the first-order phase transition (collapse) was observed. While the critical acetone concentration in the mixture at collapse, ac = 76 vol%, is independent of x, the extent of the collapse (jumpwise change in the gel volume), .1, increases with increasing salt concentration. The jumpwise change in the gel volume is accompanied by a similar change in equilibrium modulus. The swelling and mechanical behavior of ionized networks in aqueous NaCl solutions were also measured. The expected decrease in the swelling and the increase in the modulus with increasing electrolyte concentration CNaC1 was found. The theory of swelling equilibria of polyelectrolyte networks, in which the effect of electrostatic interactions of the charges on the chain and a limited chain extensibility were included, semiquantitatively describes the swelling data provided an effective concentration of the charges (lower than xs) was introduced. Mechanical behavior of networks is predominantly determined by their degree of swelling.KEY WORDS Vinylpyrrolidone Networks / Polyelectrolytes / Swelling Equilibria / Mechanical Behavior / First-Order Phase Transition / Collapse Phenomenon / Swollen polymer networks carrying low amounts of charges on the chain (1-10 mol %), when subjected to a change in the external parameters (temperature, composition of the mixed solvent, electric field and the like), undergo a first-order phase transition (collapse), at which the jumpwise change in volume of the gel can be from 10 to 1000 times. 1 -4 SANS experiments showed that in the expanded state, the chains have a coil shape, while in the collapsed state they are in globular form.5 It has been shown,2 both experimentally and theoretically, that the conditions of network formation (concentration of cross linker and diluent) and of the charge concentration have a great influence on the appearance and extent of the collapse. The jump in volume is accompanied by a jump in other physical properties, such as shear modulus, refractive index, dielectric permittivity, and the like. 2 Due to these changes, these systems are considered for use in various devices, sensors, mechanochemical actuators, 6, 7 etc. Most experimental results were obtained with charged poly(acrylamide) (PAAm), poly(N-isopropylacrylamide) (PIPAAm), and poly(N,N-diethylacrylamide) (PDEAAm) hydrogels. 1 -3 ,8 While in PAAm gels, the collapse can be brought about by the changes in the solvent composition, in PIPAAm and PDEAAm gels the transition can be induced in water, by a temperature change. With all these systems, the networks had to be prepared at high dilution (the volume fraction of polymer ...

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Section: Comparison Of the Theory Of Swelling Equilibria Of Polyelectcontrasting

confidence: 53%

Phase Transition in Swollen Gels XXIII. Effect of the Positive Charge Concentration on the Collapse and Mechanical Behavior of Poly(1-vinyl-2-pyrrolidone) Gels

Mamytbekov

Bouchal

Ilavský

et al. 1998

Polym J

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“…The effect of aging on PAM solutions was previously attributed to the weakness of the entanglements between the PAM chains. 23 These interactions, unlike the stronger covalent bonds, could change with time and modify the internal structure of the samples until some equilibrium is eventually reached.…”

Section: Resultsmentioning

confidence: 99%

Using Optical Tweezers for the Characterization of Polyelectrolyte Solutions with Very Low Viscoelasticity

et al. 2013

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Recently, optical tweezing has been used to provide a method for microrheology addressed to measure the rheological properties of small volumes of samples. In this work, we corroborate this emerging field of microrheology by using these optical methods for the characterization of polyelectrolyte solutions with very low viscoelasticity. The influence of polyelectrolyte (i.e., polyacrylamide, PAM) concentration, specifically its aging, of the salt concentration is shown. The close agreement of the technique with classical bulk rheological measurements is demonstrated, illustrating the advantages of the technique.

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“…Under alkaline conditions, PAAm was easily hydrolyzed at lower temperatures (40-70°C). The hydrolysis reaction comprised the nucleophilic addition of the hydroxyl ion (OH À ) to the carbonyl ion of acylamide and the elimination of the amine anion NH À 2 À Á [31]. The mechanism has been shown in Fig.…”

Section: Synthesis Of the Pnipa Hydrogelsmentioning

confidence: 99%

Study of the properties of hydrolyzed polyacrylamide hydrogels with various pore structures and rapid pH-sensitivities

Zhao

Sun

Lin

et al. 2010

Reactive and Functional Polymers

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Phase transition in swollen gels. 6. Effect of aging on the extent of hydrolysis of aqueous polyacrylamide solutions and on the collapse of gels

Cited by 68 publications

References 1 publication

Phase Transition in Swollen Gels XXIII. Effect of the Positive Charge Concentration on the Collapse and Mechanical Behavior of Poly(1-vinyl-2-pyrrolidone) Gels

Phase Transition in Swollen Gels XXIII. Effect of the Positive Charge Concentration on the Collapse and Mechanical Behavior of Poly(1-vinyl-2-pyrrolidone) Gels

Using Optical Tweezers for the Characterization of Polyelectrolyte Solutions with Very Low Viscoelasticity

Study of the properties of hydrolyzed polyacrylamide hydrogels with various pore structures and rapid pH-sensitivities

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