Stereoregular Poly(Phenyl Glycidyl Ethers): In Situ Formation of a Polyether Stereocomplex from a Racemic Monomer Mixture

Polymer stereocomplex formation represents a promising research area as it can improve thermal and mechanical properties of co-crystallized polymer strands of opposite chirality. Polymers that form stereocomplexes commonly feature high stereoregularity and usually require sourcing from enantiopure monomer building blocks. Herein, we report the in situ polyether stereocomplex formation from racemic epoxide monomers, i.e., substituted methyl phenyl glycidyl ethers. The bio-renewable glycidyl ethers were explored in both enantio- and isoselective ring-opening polymerizations (ROPs), resulting in isotactic poly(phenyl glycidyl ether). While the enantioselective ROP selectively resolves a single enantiomeric, isotactic polyether stereoisomer ([mm]_P≥78 %), the isoselective ROP leads to the concurrent formation of both isotactic (R)- and (S)-poly(phenyl glycidyl ether) stereoisomers ([mm]_P≥92 %) and thus results directly in a stereoisomer blend, which forms a stereocomplex. This is one of only a few polymer stereocomplexes generated directly during polymerization from a racemic monomer mixture. Stereocomplexes of the different poly(phenyl glycidyl ether)s show an increase in melting temperature of up to 76 °C, relative to the enantiopure parent polymers. The position of the methyl group at the phenyl ring determines both stereocomplex formation and the thermal properties of the resulting materials.