To improve the circularity and performance of polyolefin materials, recent innovations have enabled the synthesis of polyolefins with new structural features such as cleavable breakpoints, functional chain ends, and unique comonomers. As new polyolefin structures become synthetically accessible, fundamental understanding of the effects of structural features on polymer (re)processing and mechanical performance is increasingly important. While <i>bulk</i> material properties are readily measured through conventional thermal/mechanical techniques, selective measurement of <i>local</i> material properties near structural defects is a major characterization challenge. Here, we synthesized a series of polyethylenes with selectively deuterated segments and employed vibrational spectroscopy to evaluate crystallization and melting of chain segments near features of interest (e.g. end groups and mid-chain defects). Differences in conformational order were measured for different chain lengths and chain-end/backbone functionalities. Chain end functionality, in particular, was observed to strongly influence crystallinity and melting onset temperature of adjoining deuterated chain segments. With the ability to selectively measure conformation of specific chains or chain segments, we aim to enable more rational design of materials, blends, and (re)processing pathways to improve plastics circularity and material properties.

Selective deuteration near structural features in polyethylene: Enabling better design of polyolefins through fundamental measures

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