Polyolefins have established themselves as one of the most impactful classes of commodity thermoplastics. These materials find widespread use in single-use packaging systems, resulting in a short application lifetime and a high volume of polyolefins in commercial waste streams. Effective polyolefin recycling is complicated by the complex library of polymer structures and architectures within this broad class of polymers. Poly(ethylene) (PE), for example, commonly contains short-chain branches (SCBs) that are incorporated into the chain through the copolymerization of ethylene and various α-olefins (<i>e.g.,</i>1-hexene), resulting in linear low-density poly(ethylenes) (LLDPE) that are desired for their enhanced ductility and processability over high-density poly(ethylenes). The distribution of these branches is often non-uniform, where inter- and intramolecular heterogeneities in branch placement on the polymer backbone can result in blocky, gradient, and statistical copolymers all existing in the same LLDPE sample. To better understand the structure-property relationships in diverse polyolefin architectures, we have synthesized a series of PE diblock copolymers derived from ring-opening metathesis polymerization (ROMP) that contain branched and unbranched blocks. This bottom-up approach to model LLDPE development allows us to target molecular weights and block ratios and—due to our use of ROMP—allows for precise placement of SCBs at every eighth carbon. Measurement of the dilute solution properties of these model materials (<i>e.g.,</i> intrinsic viscosity, radius of gyration, SCB content) is paired with simulations to understand how the structure-property relationships of these polyolefins are influenced by branch length, branch content, and polymer architecture. These measurements expand our ability to identify, characterize, and separate different polyolefin architectures from complex mixtures.

Dilute solution properties of short-chain branched polyolefin block copolymers derived from ring-opening metathesis polymerization

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