Toward Polyethylene-Polyester Block and Graft Copolymers with Tunable Polarity

The synthesis and characterization of polyethylene polyester block and graft copolymers and their potential as compatibilizers in polyethylene-based polymer blends are being described. The various routes to functionalized polyethylenes and the corresponding block/graft copolymers have been compared and evaluated for their scalability to industrial scale production. Hydroxyl chain-end and randomly OH-functionalized HDPE as well as randomly OH-functionalized LLDPE were employed as macroinitiators for producing the corresponding block and graft copolymers. These materials were prepared using two different strategies. The grafting from approach entails catalytic ring-opening polymerization of lactones, i.e., epsilon-caprolactone and omega-pentadecalactone and hydroxyl-functionalized polyethylenes as macroinitiator. The alternative grafting onto approach involves the preparation of block and graft copolymers via simple and convenient transesterification of polycaprolactone or polypentadecalactone with OH-functionalized polyethylenes. The copolymers were characterized in terms of their molecular weight (SEC), chemical structure (liquid state NMR), topology (MALDI-ToF-MS), supramolecular assembly (solid state NMR), and thermal properties (DSC analysis). The applied techniques for synthesizing the copolymers allow preparation of the products with sufficiently high molecular weight of the final materials. The copolymers were tested as compatibilizers for polyethylene/polycarbonate blends. As proven by SEM analysis, addition of the compatibilizers resulted in a significant improvement of the blend morphology.