Multidisciplinary characterization of novel emulsion polymers

Abstract

A series of novel emulsion styrene-butadiene copolymer blends were characterized using a multidisciplinary approach involving both analytical and rheological measurements. The blends were composed of 50/50 w/w high molecular weight (ca. 800,000 Da) ESBR and low molecular weight (ca. 200,000 Da) ESBR, each component having a different bound styrene level. When the difference in bound styrene between the two components was greater than 18%, a two phase co-continuous morphology was observed by scanning probe microscopy, consistent with two glass transitions measured by temperature modulated DSC. Molecular weight and molecular weight distributions were characterized by both size exclusion chromatography and thermal field flow fractionation with multiangle light scattering detection. ThFFF was unique in its ability to detect ultra-high molecular weight (> 107 Da) fractions suggesting that traditional SEC often under-estimates polymer molecular weight. Blending polymers of different molecular weights and styrene levels resulted in reduced molecular weight between entanglements which, based on rheological measurements, would be expected to improve processability.