Exploring telogen chemical structure and reactivity when forming highly branched polyesters derived from ethylene glycol dimethacrylate homopolymerisation under transfer-dominated branching radical telomerisation (TBRT) conditions

Transfer-dominated Branching Radical Telomerisation (TBRT) is a free radical telomerisation reaction that allows the homopolymerisation of multi-vinyl substrates. When applied to dimethacrylates, highly branched polyesters are formed with essentially complete consumption of vinyl functional groups and without gel formation. To date, no reports of TBRT have investigated a diverse series of thiol telogens with considerable variation in chain transfer coefficients (CT) when using the same multi-vinyl taxogen (MVT). Here, the impact of CT on reaction conditions and structural telogen sub-units is studied for the homopolymerisation of ethylene glycol dimethacrylate (EGDMA). Kinetic studies explore the different rates of vinyl group consumption, and model linear telomer studies using a monovinyl taxogen investigate the distribution of sub-units that are formed when using the different telogens. The formation of a library of branched polyesters with varying telogen-derived pendant groups with weight average molecular weights up to 4 930 000 g mol-1 has allowed a detailed comparison of glass transition temperatures and the calculation of Tg infinity values using classical or modified Flory-Fox relationships. Chain transfer agents with very different reactivities modify the structures of polymers formed by TBRT, leading to options to control branching levels, and polymer properties, using a single divinyl monomer.