Miscibility windows of poly(vinyl methyl ether) with modified phenoxy resin

Blends of poly(vinyl methyl ether) with partially methylated and benzoylated poly(hydroxy ether of bisphenol A) (phenoxy resin, PH) have been studied. The optical appearance of the mixtures and their glass transition temperatures as measured by differential scanning calorimeter has been used as macroscopic criteria for miscibility. All miscible blends showed phase separation (LCST) when increasing temperature as determined by optical microscopy. The PH degree of modification reduced the intrinsic miscibility of the blends as well as the values of the cloud point temperatures. This behaviour has been qualitatively discussed in terms of the reduction of the intermolecular strong interaction sites and its influence on the association equilibria, which stabilise the blends.