Mechano-chemical Patterns in Collapsing Gels

Sasaki, Shinya; Maéda, Hiroshi

doi:10.1006/jcis.1998.5967

Cited by 8 publications

(12 citation statements)

References 13 publications

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“…The gel was immersed into the solution of given concentrations of DPC ( C DPC ) and NaCl ( C s ), pH of which was adjusted between 9 and 10 by adding a small amount of the 0.1 M NaOH solution. The diameter of the gel was measured using a computer-aided optical microscope system . For examining hysteresis, size measurements for one gel were made successively changing C DPC .…”

Section: Methodsmentioning

confidence: 99%

Salt Effects on the Volume Phase Transition of Ionic Gel Induced by the Hydrophobic Counterion Biding

et al. 2001

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The salt effects on the volume phase transition of ionic poly(acrylate) gel with a change in the concentration of hydrophobic counterion, dodecylpyridinium chloride (DPC) in outside solution of the gel is investigated. The transition concentrations increase with the NaCl concentration C s of the solution and the transition disappears at C s above 0.5 M. A hysteresis is observed for the transition concentration of DPC; that is, the deswelling transition concentration in the increasing process, C t i is significantly higher than the swelling transition concentration in the decreasing process C t d. The difference between C t i and C t d is found to increase with decrease in C s. The comparison of the gel and the polymer solution reveals the resemblance between the salt effects on their phase transitions.

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Section: Methodsmentioning

confidence: 99%

Salt Effects on the Volume Phase Transition of Ionic Gel Induced by the Hydrophobic Counterion Biding

et al. 2001

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“…The chemical structures of ionic poly(acrylate) gel and dodecylpyridinium(DP) counterion are shown in Figure . The poly(acrylate) gels were prepared by the radical copolymerization , in the aqueous solution of 1 M acrylic acid and 0.01 M N , N ‘-methylenebis(acrylamide) at 60 °C. The gels were synthesized in a glass tube (inner diameter = 0.3 mm) and in a space between two glasses separated by a 1 mm thick spacer of poly(tetrafluoroethylene) sheet.…”

Section: Methodsmentioning

confidence: 99%

Elastic Relaxations of Ionic Gel Associated with Hydrophobic Counterion

Sasaki

Koga

2002

J. Phys. Chem. B

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The tensile moduli of poly(acrylate) gel collapsed due to the hydrophobic dodecylpyridinium(DP) ion binding in the various salt concentrations were measured. It was found that the tensile force relaxed after the elongation and that the relaxation moduli strongly depended on the salt concentration, C S . The differences between the moduli at initial, Y i , and at equilibrium, Y e , were 4 × 10 5 Pa at C S ) 10 mM and 3 × 10 3 Pa at C S ) 100 mM. The substantially constant moduli, (Y i ∼ 5 × 10 5 Pa and Y e ∼ 4 × 10 4 Pa) at C S between 10 and 50 mM deeply drop at C S between 80 and 100 mM, and level off (Y i ∼ 11 × 10 3 Pa and Y e ∼ 8 × 10 3 Pa) at C S above 100 mM. However, the size of gel at C S ) 100 mM is essentially the same as that at C S ) 10 mM. This indicates that the C S -dependent attraction between the ionic network and the hydrophobic counterions seriously affects the elasticity of the collapsed gel system. The relaxation moduli, Y(t), of the gel is fitted to a function of Y(t) ) (Y i -Y e ){R 1 e -t/τ 1 + R 2 e -t/τ 2 + (1 -R 1 -R 2 )(1 + t/τ 0 ) -β } + Y e .

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“…Moreover, experiments on acrylate-acrylamide gels in a water-acetone mixture have demonstrated that a mechano-chemical coupling can drive the formation of different patterns. 6 Bubbles are observed if the gel is shrunk almost homogeneously, while rings (longitudinal wrinkles) appear if a mechanical compression (elongation) is imposed.…”

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“…Considering the competition between a bulk elastic energy density P z and the surface energy A, the variation problem reads dA + dP ¼ 0, which induces a change only in first of the two boundary conditions in eqn (6) Substituting eqn (7) into eqn(16), we find the correction of the boundary condition C J;g in eqn (12) due to the capillarity:…”

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