| Abstract
| - We have investigated the dynamics of the phase transition between swollen isotropic andshrunken nematic states for a nematic network swollen in nematic solvent. The kinetics of swelling andshrinking driven by temperature (T)-jumps across the nematic−isotropic (N−I) transition temperature(TNIG) strongly depends on the distance of destination temperature (Td) from TNIG (ΔT). When Td is farabove TNIG, the N → I transition completes fast within the T-jump, which yields the swelling process oftotally isotropic gel without coupling of N → I transition. If Td is moderately above TNIG, the N → Itransition slowly proceeds from surface toward center of gel with accompanying swelling. In this case,the total swelling process is composed of two different stages, i.e., during N → I transition and after N→ I transition: The former is a thermally activated process strongly coupled with N → I transition; thelatter is the T-independent swelling process of totally isotropic gel. When the T-quench from isotropicphase to nematic phase is sufficiently deep, the I → N transition and shrinking proceed uniformly whereasthe process is decelerated with increasing the degree of total volume change. In the case of Td slightlyabove (or below) TNIG, the onset of the N → I (or I → N transtion) is governed by heterogeneous nucleation,and the following growth of the nuclei yields considerably nonuniform swelling (or shrinking). The resultingdynamics becomes markedly slower than that observed after the T-jumps with sufficiently large ΔT.
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