Elucidating the Impact of Structural Parameters on the Glass Transition Temperatures of Bottlebrush Polymers

The glass transition of branched polymers is determined by multiple structural parameters that dictate their inter- and intramolecular interactions, and ultimately, their molecular packing in the amorphous phase. Here we examined the impact of side chain length, backbone length, molecular weight composition, and topology on the glass transition behavior of bottlebrush polymers. Through examining precision bottlebrush polymer libraries (PBP, ĐSC = 1.0), we find the infinite molecular weight Tg is reached at a specific brush length after which the effect of the side-chain length dominates. Being a factor more dominant than the backbone, side-chain length affects the Tg of bottlebrush polymers across all sizes and topology variations. To demonstrate the versatility of side chain engineering strategies, a broad range of Tg and glass transition behavior was targeted through judicious choice of side chain length, blend ratios, and brush topology.