On Some New Problems in Gels near the Volume Phase Transition

Ōnuki, Akira

doi:10.1007/978-3-642-83948-1_11

Cited by 3 publications

(1 citation statement)

References 21 publications

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“…For the ideal gel, which is homogeneously crosslinked, the nonzero elastic modulus due to crosslinks is expected to suppress the thermal concentration fluctuations and therefore small-angle scattering. 28 So far, there is no experimental observation of such suppression of small-angle scattering in the real gel. As FIG.…”

Section: Discussionmentioning

confidence: 99%

Concentration fluctuations in polymer gel investigated by neutron scattering: Static inhomogeneity in swollen gel

Koizumi

Monkenbusch²,

Richter³

et al. 2004

The Journal of Chemical Physics

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By using small-angle neutron scattering ͑SANS͒ and neutron spin echo ͑NSE͒, we have quantitatively investigated the static inhomogeneity in poly ͑N-isopropyl acrylamide͒ gel ͑PNIPA͒ in microscopic length scales of 0.015ϽqϽ0.16 A Ϫ1 , where q is a wave number of scattered neutrons. NSE revealed that at lower q(Х0.015 A Ϫ1 ), the concentration fluctuations in the PNIPA gel decays more slowly as compared to the PNIPA solution without crosslinks. According to our scenario that the slower decay found for the PNIPA gel is due to the static inhomogeneity coexisting in the swollen gel, small-angle scattering S(q) obtained by SANS has been quantitatively decomposed into thermal and static scattering components, respectively, S th (q) and S st (q). It was further revealed that ͑i͒ the q-region where S st (q) becomes dominant is closely related to that for the abnormal butterfly scattering under stretching, and ͑ii͒ as the temperature increases toward the temperature for volume phase transition, S st (q) of a squared Lorentzian shape increases more drastically than S th (q) of a Lorentzian shape. These findings were quantitatively understood in the theoretical framework by Panyukov and Rabin ͓Macromolecules 29, 7960 ͑1996͔͒ or by Onuki ͓J. Phys. II. France 2, 45 ͑1992͔͒, taking into account stress-fluctuation coupling under coexistence of the inherent structural heterogeneity in the real gel. We further found that the static inhomogeneity showing S st (q) seems to relate to the necklacelike microstructure, appearing after a shallow quench into the collapsed phase.

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Section: Discussionmentioning

confidence: 99%

Concentration fluctuations in polymer gel investigated by neutron scattering: Static inhomogeneity in swollen gel

Koizumi

Monkenbusch²,

Richter³

et al. 2004

The Journal of Chemical Physics

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Enhancement of inhomogeneities in gels upon swelling and stretching

Bastide

Mendes

Boué³

et al. 1990

Makromolekulare Chemie. Macromolecular Symposia

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In this paper, it is shown how a percolation process can be used to describe the inhomogeneities of polymer concentration, appearing in gels prepared by random crosslinking of a semi‐dilute solution, and how they are modified by swelling or stretching of the network. Neutron scattering experimental data are compared to the predictions of this model in the isotropic and anisotropic cases. A good agreement is found. In particular, “abnormal” butterfly patterns in the iso‐intensity curves have been detected, as expected from the model.

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