Morphology of phase separated blends of poly(cyclohexyl methacrylate) with poly(vinyl acetate)

Blends of poly(vinyl acetate) (PVAc) and poly(cyclohexyl methacrylate) (PCHMA) labeled by copolymerization with 4-methacryloylamine-4'-nitrostilbene (Sb), with (1-pyrenylmethyl)methacrylate (Py) or with 3-(methacryloylamine)propyl-N-carbazole (Cbz), were prepared by casting dilute solutions in tetrahydrofurane (THF) or chloroform onto silanized glass plates. The resulting films were studied by epifluorescence microscopy, microfluorescence spectroscopy, DSC and optical microscopy. Epifluorescence micrography probes the chemical composition of the different regions in phase separated blends, with black areas corresponding to PVAc rich regions and colored areas corresponding to labeled PCHMA rich regions. The technique also visualizes primary and secondary morphologies, which depend on the composition of the polymer blend and on the casting solvent. Mixtures containing 80 wt % PCHMA show, in general, a bicontinuous primary morphology suggesting a spinodal demixing mechanism. Solvent effects are particularly relevant for 50% and 20% PCHMA samples showing morphologies composed of PCHMA rich domains, in a matrix of solvent-dependent compositions. Samples cast from chloroform are more homogeneous and the matrix is always highly fluorescent. In contrast, the domains of samples cast from THF are heterogeneous in size and shape and the matrix is non-fluorescent, being thus formed by nearly pure PVAc. Small voids are formed in the polymer-air interface. They are submicrometric for THF cast films and disappear with annealing at 122degreesC. For chloroform cast samples they are much less frequent and appear well ordered, forming a mostly hexatic two dimensional network. (C) 2003 Wiley Periodicals.