Phase segregation in SAN/PMMA blends probed by rheology, microscopy, and inverse gas chromatography techniques

Phase segregation in the poly(styrene-co-acrylonitrile)/poly(methyl methaerylate) (SAN/PMMA) blend with lower critical solution temperature (LCST) was assessed by linear viscoelastic rheology, optical microscopy, and inverse gas chromatography (IGC) techniques for various blend compositions. At low temperatures, the blends showed a classical behavior of homogeneous polymer melts, whereas in the vicinity of phase segregation, a shoulder in the storage modulus and in the linear relaxation modulus G(t) was observed. The width of such a low-frequency/longer-time plateau and the terminal relaxation time were found to increase with temperature. Such a behavior was attributed to variable morphologies appearing at different temperatures. The development of the morphology was found to take place within a given interval of temperature rather than at a single critical temperature. Optical microscopy and IGC analyses supported the observed peculiar behavior of such a blend. Time-temperature superposition, origin of elasticity, and the Fredrickson and Larson theory were discussed in light of the obtained results.