Abstract
We have investigated the order-disorder transition (ODT) of a lamellae-forming PEO-b-P4VP exhibiting LCOT behavior and examined the solubilization behavior of P4VP homopolymer in its blends with the PEO-b-P4VP. PEO-b-P4VP exhibited ODT upon cooling. The temperature-dependent SAXS measurement revealed that as the TODT was approached on cooling, the long-range order of the lamellar structure was still well preserved, indicating that the thermal noise effect, which is prevalent in the conventional UCOT system, did not play a major role, such that the phase transition process may approach the mean-field behavior. When its blends with H4VP, which can be solubilized into the P4VP microdomains, also displayed LCOT behavior, where they showed a order-to-disorder transition (ODT) upon cooling. In the microphase-separated state, the interdomain distance D of the lamellae structure was found to increase with increasing molecular weight of H4VP (MH4VP) and the H4VP formed wet or dry brush solubilization. In contrast to the classical system of PS-b-PI / homopolymer blends, the critical value of r (MH4VP/MB4VP) below which the system shows completely wet brush behavior was found to lie significantly lower than 1.0. This phenomenon was attributed to the enhanced roles of both repulsive interaction energy and conformational entropy at high temperature, so as to hinder the uniform solubilization of H4VP. Even when the H4VP was uniformly solubilized in the P4VP microdomain, the lamellae morphology remained stable even when the overall P4VP composition was highly unsymmetric.