Solvent Effects in Grafting-through Ring-Opening Metathesis Polymerization

Ring-opening metathesis polymerization (ROMP) utilizing Grubbs’ third-generation catalyst ((H2IMes)(Cl)2(pyr)2RuCHPh) shows the characteristics of living polymerizations, including molecular weights increasing with monomer conversion and ability to make (multi)block copolymers. However, irreversible termination reactions still occur due decomposition, leading terminated chains, especially in context sterically demanding monomers such as macromonomers (MMs). In this work, we performed identical ROMP on three different MMs six solvents commonly used varying levels purity. The included ethyl acetate (EtOAc), dichloromethane (CH2Cl2), chloroform (CHCl3), toluene, tetrahydrofuran (THF), N,N-dimethylformamide (DMF). All polymerizations were conducted under air targeting a bottlebrush polymer backbone degree (Nbb) 100. norbornene α chain end had weight (Mn) ∼4 kg/mol. They one polystyrene MM bromine ω two poly(n-butyl acrylate) either or trithiocarbonate group end. Solvent choice, some cases level purity, led significant differences propagation rate these grafting-through reactions. Of tested, rates EtOAc CH2Cl2 approximately 4-fold 2-fold faster, respectively, than that CHCl3, THF for all MMs. Propagation was much slower DMF other par tested. purity solvent profound effect rate: case EtOAc, purification decrease rate; contrast, required observe full polymer. functional did not influence ROMP. Utilizing UV–vis spectroscopy measure main route ROMP, uncovered dramatic effects, where decomposed over 10 times faster toluene. Finally, studies Nbb = 500 1000 revealed demonstrated highest “livingness” These results will enable synthesis complex architectures using high character.