Preparation of nano-TiO2/polyurethane emulsions via in situ RAFT polymerization

Stable nano-TiO 2 /polyurethane (PU) emulsions were prepared via in situ reversible addition-fragmentation chain transfer (RAFT) emulsion polymerization of 2-hydroxyethyl acrylate (HEA)-capped PU macromonomer, using azobisisobutyronitrile (AIBN) as a radical initiator and 2-{[(butylsulfanyl)carbonothioyl]sulfanyl} propanoic acid (BCSPA) anchored onto TiO 2 nanoparticles (TiO 2 -BCSPA) as a RAFT agent. When the molar ratio of AIBN to TiO 2 -BCSPA was changed from 1:3 to 1:10, the polydispersity index (PDI) of polymers in the emulsions decreased from 1.83 to 1.06, due to more effective RAFT polymerization in the emulsions. The TiO 2 nanofillers were well-dispersed throughout the polymer films . The tensile strengths of the nanocomposite films were significantly enhanced due to coordination bonding between the TiO 2 nanofillers and the –COOH end groups of the polymers, as evidenced by the FT-IR spectral data.