Direct RAFT polymerization of an unprotected isocyanate-containing monomer and subsequent structopendant functionalization using click-type reactions

The controlled reversible addition-fragmentation chain transfer (RAFT) homopolymerization of an unprotected isocyanate-containing monomer, in this case 2-(acryloyloxy)ethylisocyanate (AOI), is reported. The polymerization conditions were optimized in terms of the choice of RAFT chain transfer agent (CTA), polymerization temperature and the reaction medium. Direct RAFT polymerization of AOI requires a neutral CTA, and relatively low reaction temperature to yield AOI homopolymers with low polydispersities. Efficient side-chain functionalization of poly(2-(acryloyloxy)ethylisocyanate) (PAOI) homopolymers was achieved via reaction with model amine, thiol and alcohol compounds yielding urea, thiourethane and urethane derivatives, respectively. Reactions with amines and thiols (in the presence of base) were rapid, quantitative and efficient. However, the reaction with alcohols catalyzed by dibutyltin dilaurate (DBTDL) was relatively slow but proceeded to completion. Selective reaction pathways for the addition of difunctional ethanolamine and mercaptoethanol were also investigated.