Catalysts and Process Design for Living Aqueous Polymerization to Ultra High Molecular Weight Polyethylene Nanocrystals

Abstract

Assembly of anisotropic shape nanoparticles holds potential to form superstructures and materials with yet unmet properties. However, routes to anisotropic polymer particle dispersions of high solids content are lacking. Polyethylene, an important synthetic material, can be obtained in the unusual form of nanoscale platelet-like single crystals by aqueous catalytic polymerization with Ni(II) salicylaldiminato catalysts. Generation of such nanocrystals with uniform shapes and sizes is highly desirable, considering formation of materials with well-defined properties by their assembly. Indeed, this would require a strictly living chain growth and, simultaneously, a living particle growth in absence of any termination reactions.This work reports the concept of such a living catalytic polymerization of ethylene in aqueous surfactant solution, resulting in particles grown by a single active site and composed of a single ultra high molecular weight polyethylene (UHMWPE) chain. These findings are a relevant step towards polymer materials based on nanoparticle assembly.