Reversibility of thermodynamic lower critical solution temperature phenomenon in miscible poly(ε-caprolactone)/poly(benzyl methacrylate)

Abstract

Differential scanning calorimetry and optical microscopy were performed to examine the reversibility of phase separation at above the lower critical solution temperatures in a miscible poly(ε-caprolactone) (PCL)/poly(benzyl methacrylate) (PBzMA) blend system. Upon heating, phase separation occurred via a binodal nucleation and growth (NG) mechanism at above 240 °C, which is a lower critical solution temperature (LCST). The pattern of phase domains suggests that the phase separation was meta-stable. Interestingly, the LCST phase separation was found to be readily reversible to original homogeneity upon cooling at regularly accessible rates. A major factor may be that the temperature window between the LCST curve and blend T_g curve is wide, resulting in a convenient temperature range for the polymer chains to kinetically reorganize to a state favored by the thermodynamic conditions.