Functionalized hyperbranched polyethylenes by chain walking ethylene copolymerization

The development of functionalized polymers is an exciting and important field of research. Late transition metal catalysts, particularly Pd-diimine catalysts, possess unique characteristics that allow for the synthesis of novel functionalized polyethylenes. The main theme of this research is to develop new hyperbranched polyethylenes possessing enhanced characteristics and investigate their potential applications.;A unique one-pot polymerization procedure using a Pd-diimine catalyst for ethylene copolymerization with 1,4-butanediol diacrylate (BOA) at elevated concentrations, was used to synthesize low viscosity hyperbranched polyethylenes tethered with controlled amounts of acryloyl functionality with minimal intermolecular cross-linking. The success of this procedure is the use of BDA concentrations above the critical gelation concentration. The diacrylate comonomer is copolymerized predominantly following a mono-insertion patter due to kinetic suppression of intermolecular cross-linking. A range of polymers were successfully synthesized, possessing a range of acryloyl functionality.;In order to control polymer chain topology by ring incorporation, chain walking ethylene copolymerization with cyclopentene as the ring-forming comonomer was carried out. A range of polymers containing various cyclopentene contents were successfully synthesized to study the linearization effect of ring incorporation on polymer chain topology. The polymers were characterized with 13 C nuclear magnetic resonance (NMR) spectroscopy, triple-detection gel permeation chromatography (GPC), and rheometry. It was found that ring incorporation was primarily isolated cis-1,3 ring units with a small fraction of cis-1,2 ring units. Ring incorporation caused significant chain topology linearization and enhanced zero-shear viscosity of the polymer melts with an increase in ring content, despite the decreasing polymer molecular weight. The results from this study support the proposed blocking effect of backbone-incorporated rings on catalyst chain walking and ring incorporation can be used as an effective parameter for the tuning of polyethylene chain topology.;Hyperbranched polyethylenes are a new grade of polymers that possess unique structures resulting from chain walking ethylene polymerization, and these synthesized polymers have great potential as viscosity index improvers in lubricant formulation. Hyperbranched polyethylenes possess outstanding shear stability due to their highly branched compact chain structures, however, this compact structure compromises their viscosity thickening power. In a one-pot procedure, a range of hyperbranched polymers were synthesized by chain walking ethylene copolymerization with 1,4-butanediol diacrylate as difunctional cross-linker. The synthesized cross-linked polymers were characterized and lubricant formulations were studied. The enhanced molecular weight, due to cross-linking, improved the polymers viscosity thickening power, however, their shear stability was compromised. Compared to linear analogues, their compromised shear stability is still significantly better.