Effect of the morphology of two phase polymer blends on glass transition temperature

Blends of poly(cyclohexylmethacrylate), PChMA, with poly(vinylacetate), PVAc, were prepared by casting THF and chloroform solutions. A calorimetric and morphologic study was performed. Differential scanning calorimetry investigations of the blends show two glass transition temperature that give evidence of inmiscibility. For polymer less flexible (PChMA) was observed an enhancement of Tg by 20 °C approximately in blends of PVAc-rich composition. Epifluorescence microscopy, using PChMA labelled by copolymerization pirenyl-methylmethacrylate, Py, shows also phase separation providing imaging of the distribution of PChMA in the different domains and in the matrix. Blends containing 80% w/w PChMA show a bicontinuous primary morphology suggesting a spinodal phase separation mechanism. The 50 and 20% PChMA samples show morphologies composed of PChMA-rich domains in a matrix composed by PVAc mainly. Blends with domain–matrix morphology present a higher Tg than pure homopolymer more rigid (PChMA) due to packing in microphases in matrix of more flexible polymer (PVAc).