PHASE-TRANSITIONS IN THIN-FILMS OF BLENDS OF POLY(METHYLMETHACRYLATE)AND CRYSTALLIZABLE POLY(ETHYLENE OXIDE)

Phase separation in thin films of blends of amorphous PMMA and crystal line PEO was studied. Films of various thicknesses were prepared by ca sting 3% solutions in chloroform onto a silicate glass plate and a hyd rophobic glass substrate. Phase diagrams were constructed by means of differential thermal analysis (by determining T-m of PEO in the blends ) and light transmission. Phase separation occurs differently in diffe rent composition ranges of the system, depending on the molecular mass es of the constituent polymers: either the second amorphous (the bound ary curves are binodals with the upper critical point) or a crystallin e phase (with liquidus curves) is formed. The crystallization temperat ure of PEO in the blend, as determined by small-angle anisotropic ligh t scattering, is dependent on the film thickness, the molecular masses of the components, the composition of the blend, and the nature of th e substrate. The results were discussed in terms of present-day views on the structure of surface adsorption layers in polymers.