Hyperbranched polyethylenes by chain walking polymerization: synthesis, properties, functionalization, and applications

Structurally different from existing polyethylene grades, hyperbranched polyethylenes (HBPEs) synthesized by Pd-diimine-catalyzed chain walking polymerization represent a novel class of polyethylene materials with unprecedented chain architectures and unique physical properties. A large number of research investigations have been carried out in the area in the past decade, and have led to the successful synthesis of a broad range HBPEs of various controlled chain topologies, molecular weights, and functionalities by tuning polymerization parameters and/or catalyst structures. Meanwhile, some new specialty applications of these materials have also been demonstrated in various fields ranging from lubricant additives to polymer building blocks to nanoencapsulation, with some interesting performance properties discovered. This review aims to summarize the developments in this area.