Viscoelasticity near the sol-gel transition

Martin, James E.; Adolf, Douglas Brian; Wilcoxon, J. P.

doi:10.1103/physreva.39.1325

Cited by 199 publications

(181 citation statements)

References 29 publications

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“…Indeed, the gel time is the time needed for the material to behave as one single macromolecule under some shear rate. At this point, moduli are predicted [53][54][55] and experimentally observed to scale with the frequency (f) according to the scaling exponent theory, where G′(ω)=G″(ω)=ω ∆ , ω=2πf and ∆ is the scaling exponent [53 ; 56-57]. In addition, tan δ shows at the gel time a universal constant value (δ=∆(π/2)) [56].…”

Section: Rheological Behaviourmentioning

confidence: 99%

Silica reinforced triblock copolymer gels

Theunissen

Overbergh

Reynaers

et al. 2004

Polymer

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The effect of silica and polymer coated silica particles as reinforcing agents on the structural and mechanical properties of polystyrene-poly(ethylene/butylene)-polystyrene (PS-PEB-PS) triblock gel has been investigated. Different types of chemically modified silica have been compared in order to evaluate the influence of the compatibility between gel and filler.Time-resolved SANS and small-angle X-ray scattering (SAXS) shows that the presence of silica particles affects the ordering of the polystyrene domains during gelsetting. The scattering pattern of silica-reinforced gels reveals strong scattering at very low q, but no structure and formfactor information. However, on heating above the viscoelastic to plastic transition, the 'typical' scattering pattern of the copolymer gel builds-up. All reinforced gels are strengthened by the addition of the reinforcing agent. The transitions from a viscoelastic rubber to a plastic fluid and from a plastic fluid to a viscoelastic liquid are shifted to more elevated temperatures when silica is added to the triblock copolymer gel.

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Section: Rheological Behaviourmentioning

confidence: 99%

Silica reinforced triblock copolymer gels

Theunissen

Overbergh

Reynaers

et al. 2004

Polymer

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“…Close to the gel point, under some circumstances, the rheological properties also obey scaling forms [9,10,11,12,13,14,15]. The shear relaxation modulus G(t) is a power law in time (t) and the complex viscosity η * (ω) is a power law in frequency (ω):…”

Section: Introductionmentioning

confidence: 99%

Dynamic scaling in entangled mean-field gelation polymers

et al. 2006

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We present a simple reaction kinetics model to describe the polymer synthesis used by Lusignan et al.[1] to produce randomly branched polymers in the vulcanization class. Numerical solution of the rate equations gives probabilities for different connections in the final product, which we use to generate a numerical ensemble of representative molecules. All structural quantities probed in ref. [1] are in quantitative agreement with our results for the entire range of molecular weights considered. However, with detailed topological information available in our calculations, our estimate of the 'rheologically relevant' linear segment length is smaller than that estimated in ref [1]. We use a numerical method [2] based on tube model of polymer melts to calculate the rheological properties of such molecules. Results are in good agreement with experiment, except that in the case of the largest molecular weight samples our estimate of the zero-shear viscosity is significantly lower than the experimental findings. Using acid concentration as an indicator for closeness to the gelation transition, we show that the high-molecular-weight polymers considered are at the limit of meanfield behavior -which possibly is the reason for this disagreement. For a truly mean-field gelation class of model polymers, we numerically calculate the rheological properties for a range of segment lengths. Our calculations show that the tube theory with dynamical dilation predicts that, very close to the gelation limit, contribution to viscosity for this class of polymers is dominated by the contribution from constraint-release Rouse motion and the final viscosity exponent approaches Rouse-like value.

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“…where D has been termed the critical relaxation exponent, relaxation exponent, or viscoelastic exponent [9,18,19]. Near the sol-gel transition, many viscoelastic quantities diverge as powers of the distance of the bond probability p from the gel a)…”

Section: Introductionmentioning

confidence: 99%

Universal aspects of hydrogel gelation kinetics, percolation and viscoelasticity from PA-hydrogel rheology

Adibnia

Hill

2016

Journal of Rheology

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Polyacrylamide (PA) hydrogels have been studied extensively, but fundamental aspects of their gelation kinetics, percolation dynamics, and viscoelasticity are still not well understood. This paper focuses on the rheology of PA hydrogels having unusually low monomer concentrations. These furnish loss tangents that span four orders of magnitude when varying the crosslinker concentration [...] Close correspondence of the exponents with those of Adam et al. for the radical copolymerization of a di↵erent material supports the long-standing hypothesis that dynamics at the gel point are universal for a prescribed gelation mechanism

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Viscoelasticity near the sol-gel transition

Cited by 199 publications

References 29 publications

Silica reinforced triblock copolymer gels

Silica reinforced triblock copolymer gels

Dynamic scaling in entangled mean-field gelation polymers

Universal aspects of hydrogel gelation kinetics, percolation and viscoelasticity from PA-hydrogel rheology

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