Basic Investigation of Addition Fragmentation Chain Transfer Agents in Photopolymerization of Methacrylic Monomers

Addition fragmentation chain transfer agents (CTAs) are an upcoming important group of compounds used for controlling radical polymerization.1 Generally, AFCT reagents are known from thermal radical polymerization in solution, photoinitiated, controlled bulk polymerization is rarely found in literature. Transforming an uncontrolled radical chain reaction into a controlled radical chain growth/step growth process, lowers and narrows the molecular weight distributions of the formed polymers.2 In this work, new chain transfer reagents based on β-allyl sulfones were synthesized and tested. The properties, molecular weights and the polydispersity of β-allyl sulfone regulated methacrylate polymers are highly dependent on the electron withdrawing moiety, attached to the β-carbon of the β-allyl sulfone CTA. The photoreactivity, influence on the chain length, conversion of monomer and CTA, thermal and mechanical properties (photo-DSC, NMR, RT-NIR photorheology, DMTA,) of methacrylic resins and polymers with β-allyl sulfones as CTA, were investigated.