Phase separation dynamics of polycarbonate/polymethyl methacrylate blends. II. Temperature jumps above an immiscibility loop

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Abstract
Blends of polycarbonate (PC) and moderately low molecular weight polymethyl methacrylate (PMMA) reveal an immiscibility loop in which an upper critical solution temperature (UCST) is located above a lower critical solution temperature (LCST). Temperature jump (T jump) experiments were conducted on a 40/60 PC/PMMA composition from a single phase (150 °C) to two-phase temperatures above the immiscibility loop (205–241 °C). Phase separation first occurs, then is accompanied by phase dissolution. The early stage of phase separation is explicable in terms of the linearized Cahn–Hilliard theory. The late stage of SD follows the power-law relationship with the exponents of −1/3 and 1 as predicted by the cluster theory of Binder and Stauffer. The universal curve was established with dimensionless variables of Qm and τ. The late stage data were analyzed in accordance with the recent scaling laws of Furukawa. Time evolution of structure function exhibits universality in the late stages of spinodal decomposition. The shape of the structure function can be scaled with slopes of 2 and −6 for qqm regions, respectively. At a later time, phase dissolution takes place and the system returns to a single phase.

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