Targeted Chemical Functionalization of the Amorphous Phase in Polyolefins via Controlled Solvent Swelling.

Postpolymerization modification of polyolefins enables direct introduction of functionality into high-volume, low-cost commodity materials, affording access to functional materials that are otherwise challenging to synthesize directly from monomers. However, traditional postpolymerization modification strategies result in randomly distributed functionalization along the polyolefin backbone, which can disrupt crystallinity and degrade the thermomechanical properties of the derived polymers. Crystallite-templated postpolymerization functionalization has recently emerged as a promising strategy to overcome these limitations, yet existing approaches often require specially prepared semicrystalline gels. Here, we report a swelling-assisted postpolymerization functionalization strategy that directly leverages the semicrystalline morphology of melt-processed polyolefins. In this process, the chemical reagents are selectively introduced to the amorphous phase of polymers for a targeted functionalization reaction at elevated temperatures. The resulting functionalized polyolefins largely retain the melting temperature and crystallinity of their unmodified counterparts across multiple grafting monomers, highlighting a practical and versatile platform for producing functional polyolefins with a preserved semicrystalline microstructure and bulk properties directly from commercial feedstocks.