Optimization of immiscible polymer blends compatibilized with multiblock copolymers

This dissertation presents work to help understand the compatibilization of polymer blends with multiblock copolymers. Due to their blockiness and possible multiple interface crossings, multiblock copolymers have been hypothesized to be effective compatibilizers. The first part of this project involved synthesizing multiblock copolymers with alternating blocks of styrene and methyl methacrylate. Triblock, pentablock, and heptablock multiblock copolymers were synthesized by atom transfer radical polymerization techniques. This method is novel in that the resultant copolymers were very blocky in nature, and yet can be synthesized regardless of the direction of cross-propagation.; Next, these styrene/methyl methacrylate multiblock copolymers and other copolymer structures were analyzed as compatibilizers for polystyrene and poly(methyl methacrylate). This study provided a model system for the compatibilization of PS/PMMA interfaces by copolymers with varying architectures or structures. Compatibilization was determined by analysis with the asymmetric double cantilever beam test. Optimum strengthening for this system was observed with maximum number of blocks that are longer than a critical block length. Dependence of the interfacial fracture toughness on copolymer composition was not observed for the multiblock copolymers studied. In addition, block length of multiblock copolymers influences interfacial modification. Increasing block lengths in multiblock copolymers of a given architecture increased interfacial adhesion and block lengths greater than 21,000 are required for adequate anchoring in a PS/PMMA system.; Finally, a multiblock compatibilizer used in commercial applications was studied. Multiblock or blocky chlorinated polyethylenes (bCPE's) were evaluated as compatibilizers of poly(vinyl chloride) and polyolefin elastomers. Compatibilization was determined by ADCB and peel test experiments. A series of bCPE's with varying composition (% chlorine) and molecular weights was compared to one randomly distributed chlorinated polyethylene (rCPE). Results indicate that improvement in the interfacial adhesion between PVC and POE was more pronounced with the bCPE's than with rCPE. In addition, the optimum bCPE composition was determined to be 20% chlorine and the interfacial adhesion force was found to increase with increasing molecular weight. The POE/CPE interaction was found to govern the ability of chlorinated polyethylene to compatibilize PVC and POE.