Impact of Macromonomer Molar Mass and Feed Composition on Branch Distributions in Model Graft Copolymerizations.

Graft polymers are useful in a versatile range of material applications. Understanding how changes to the grafted architecture, such as the grafting density (), the side-chain degree of polymerization (), and the backbone degree of polymerization (), affect polymer properties is critical for accurately tuning material performance. For graft-through copolymerizations, changes to and are controlled by the macromonomer degree of polymerization () and the initial fraction of the macromonomer in the feed (), respectively. We show that changes to these parameters can influence the copolymerization reactivity ratios and, in turn, impact the side-chain distribution along a graft polymer backbone. Poly((±)-lactide) macromonomers with values as low as ca. 1 and as high as 72 were copolymerized with a small-molecule dimethyl ester norbornene comonomer over a range of values (0.1 ≤ ≤ 0.8) using ring-opening metathesis polymerization (ROMP). Monomer conversion was determined using H nuclear magnetic resonance spectroscopy, and the data were fit with terminal and nonterminal copolymerization models. The results from this work provide essential information for manipulating and while maintaining synthetic control over the side-chain distribution for graft-through copolymerizations.