iPP/PE Multiblock Copolymers for Plastic Blend Recycling Synthesized by Coordinative Chain Transfer Polymerization

Recycling of blends of widely used plastics is a key challenge of the envisioned circular economy, and thus, protocols permitting the efficient synthesis of effective compatibilizers are highly desirable. We report herein that coordinative chain transfer polymerization permits the efficient one-pot synthesis of multiblock architectures of strictly linear polyethylene or high-density polyethylene (HDPE) and isotactic polypropylene (iPP). Various block copolymers having an iPP backbone and HDPE side chains were synthesized and used to compatibilize HDPE/iPP plastic blends. The synthesized block copolymers differ in their overall molecular weights and have different HDPE side chain lengths and numbers. A block copolymer with a molecular weight of Mp = 33,700 g × mol–1 including 4.5 HDPE side chains with a molecular weight of Mn = 600 g × mol–1 showed the highest efficiency for compatibilizing 30/70 wt % blends of HDPE/iPP with a 5 wt % compatibilizer addition. This block copolymer is also superior to commercially available compatibilizers.