RAFT polymerization of N-isopropylacrylamide and acrylic acid under γ-irradiation in aqueous media

The ambient temperature (20 degrees C) reversible addition fragmentation chain transfer (RAFT) polymerization of N-isopropylacrylamide (NIPAAm) and acrylic acid (AA) conducted directly in aqueous media under gamma-initiation (at dose rate of 30 Gy h(-1)) proceeds in a controlled (typically M-w/M-n < 1.2) to near quantitative conversions and up to number-average molecular weights of 2.5 x 10(5) g . mol(-1) for PNIPAAm and 1.1 x 10(5) g . mol(-1) for PAA via two water-soluble trithiocarbonate chain transfer agents, i.e., S,S-bis(alpha,alpha'-dimethyl-alpha-acetic acid)trithiocarbonate (TRITT) and 3-benzylsulfanylthiocarbonylsulfanyl propionic acid (BPATT). The generated polymers are successfully chain extended, which suggests that the RAFT agents are stable throughout the polymerization process so that complex and well-defined architectures can be obtained.