Preparing Degradable Polymers with Promising Mechanical Properties by Hydrogen Transfer Polymerization

Hydrogen transfer polymerization (HTP) of vinyl monomers with active protons has resulted in heterochain polymers with attractive biodegradability and biocompatibility, which should enable it to be one of the most promising synthetic techniques. However, the molecular weight of the resultant polymers from HTP has been shown to be rather low, such that the products have nearly no practical application. The present work focuses on employing HTP to synthesize high-molecular-weight polymers and preparing biomaterials with good mechanical properties. Detailed investigations into the polymerization process suggested that introducing a small amount of diolefin and catalyst at the last stage of HTP of 2-hydroxyethyl acrylate (HEA) could result in a polymer with a weight-average molecular weight up to 355.8 kg/mol. During this process, diolefin worked as a coupling agent, which could both react with hydroxyl groups by oxa-Michael addition and combine with double bonds through Rauhut–Currier (RC) reactions. The resultant polymer exhibited abundant vinyl bonds existing both in the middle and at the termini and hence can be directly used as a macromonomer for biodegradable materials after UV curing with microfluidic spinning. On the basis of this strategy, the copolymerization of HEA and acrylamide (Am) was conducted, and the maximum tensile strength of the product reached as high as 30 MPa with an elongation percentage of 27.8%. What is more, the corresponding materials not only showed very good degradability but also had nearly no cell toxicity, instead helping to enhance cell viability.