COMPRESSIBILITY OF 2 POLYMER BLEND MIXTURES

Small-angle neutron scattering measurements have been performed on two polymer blend systems under pressure. Deuterated polystyrene (PSD)/poly(vinyl methyl ether) (PVME) and PSD/poly(butyl methacrylate) (PBMA) blends have been investigated over a range of temperatures and pressures. For the PSD/PVME blend, three compositions were investigated, whereas for the PSD/PBMA. system, only one composition was measured. It was found that pressure has the effect of enhancing miscibility for both blends. Our PSD/PVME measurements have shown strong pressure effects on the scattered intensity but no weakening of the composition dependence of the Flory-Huggins chi parameter under applied pressure; this eliminates compressibility as a possible cause for the origin of the composition dependence of chi in this blend system. Moreover, both the entropic part, C, and the enthalpic part, D, of the chi parameter (chi = C + D/T, where T is absolute temperature) were found to depend on pressure.