Structure-property relations in reaction-induced, phase-separated poly(2-phenoxyethyl acrylate)/polystyrene blends

Structure-property relations were studied in reaction-induced, phase-separa ted polymer blends. An amorphous-amorphous system consisted of polystyrene (PS) dissolved in the monomer 2-phenoxyethyl acrylate (POA). When the POA w as polymerized to poly(2-phenoxyethyl acrylate) (PPOA), phase separation an d phase inversion were induced, and a polymer blend was formed. The reactio n kinetics were measured by monitoring the reduction in the intensity of th e C=C stretching vibration band in the Raman spectrum of POA. The phase sep aration kinetics were determined using light transmission experiments and w ere combined with the reaction kinetics so that a ternary phase diagram cou ld be defined for the reactive system. Structure development was monitored using small-angle laser light scattering (SALLS) and optical microscopy, wh ich showed that spinodal decomposition was the mechanism of liquid-liquid p hase separation. Plots of the relative invariant with time showed an increa se in the degree of phase separation. The Fourier transforms of the microsc opy images had peaks in the radial intensity distributions, again implying that spinodal decomposition was the phase separation mechanism. Tensile tes ting showed that PPOA was soft and rubbery at 20 degreesC. Both PS and PPOA had comparable toughness when tested to failure; however, the blend contai ning 17 wt% PS had a toughness more than 10 times that of either PS or PPOA in isolation. Both modulus and tensile strength increased with PS content, while the ultimate strain decreased. The Nielsen model best described the tensile modulus data, providing further evidence for co-continuous phase st ructure.