Novel Elastomers Prepared by Grafting n-Butyl Acrylate from Polyethylene Macroinitiator Copolymers

A series of polyethylene-based macroinitiators bearing atom transfer radical polymerization (ATRP) initiator functionalities were prepared by copolymerizing norbornen-2-yl-2-bromo-2-methylpropanoate ( 3 ) with ethylene using N -(2,6-diisopropylphenyl)-2-(2,6-diisopropylphenyl-imino)isobutanamidato]-Ni(η 1 CH 2 Ph) (PMe 3 ) ( 1 ) and bis(1,5-cyclooctadiene)nickel ( 2 ). The content of 3 was increased from 2 to 16 mol %, and the mechanical properties of the resulting macroinitiators were investigated using monotonic and step cyclic stress−strain tests. With increasing 3 content, the product transitioned from plastically deforming PE to elastomeric PE (at 10 mol % 3 ) to a brittle polynorbornene-like material. Upon grafting with n -butyl acrylate (nBA) using ATRP, the new materials became significantly softer and more elastomeric in comparison to their parent macroinitiators. Increasing nBA content did not break up the PE crystallites, but instead diluted the overall crystallinity and decreased the glass transition temperature of the products. The highest performing acrylate-containing polyolefin elastomer exhibited an elongation at break of 780% strain and a recovery of 83% at 400% strain.