Tailored Polymer Architectures Enabled by Monomer-Selective Reactivity of a Dithiane Derivative

The material properties of polymers are dictated not only by composition but also by architecture. Polymers can exist as linear chains, cross-linked networks, and branched systems among others. However, more complex architectures, such as stars or bottlebrush polymers, have      garnered attention due to the tunability of their mechanical, chemical, and rheological properties. Synthesis of these architectures remains a challenge in the field of polymer chemistry. Recent works with 1,2-dithianes have suggested that its role in polymerizations is monomer-dependent and stimulus-dependent     . Under UV light, it can act as a comonomer in the presence of acrylate monomers, or as an initiator when paired with methacylate monomers. However, the exact mechanism of the polymerization is under study.

In this work, the reactivity of a dithiane derivative was explored under various polymerization conditions. Commercially available dithiothreitol is first cyclized to afford the dithiane product via oxidation with dimethyl sulfoxide under neat conditions. Subsequently, esterification with bromoisobutyryl bromide affords the target compound bearing two initiation sites for atom transfer radical polymerization (ATRP). Polymerization with acrylate monomer via ambient condition ATRP results in a polymer with a narrow dispersity with the disulfide ring intact, at the center of the chain. UV polymerizations led to side reactions resulting in the formation of poorly defined polymers. It was observed that under UV light, the dithiane molecule isomerizes to the dithiohemiacetal product and acting as a chain transfer agent. The final polymers were analyzed by nuclear magnetic resonance and gel permeation chromatography to confirm their composition and size distribution. Future work      will investigate the behavior of the dithiane derivative under thermal polymerization conditions.