Gamma radiation induced synthesis of poly(N-isopropylacrylamide) mediated by Reversible Addition–Fragmentation Chain Transfer (RAFT) process

• Poly(N-isopropylacrylamide) is synthesized by RAFT-mediated radiation induced polymerization.
• Dispersities of polymers are narrow Ɖ≤1.18, proving the controlled fashion of polymerization.
• By proper selection of [monomer]/[RAFT] ratio and conversion, MW range of 2400–72400 was achieved.
• Phase transition of PNiPAAm synthesized by RAFT is sharper than PNiPAAm synthesized by free radical polymerization.

Poly(N-isopropylacrylamide) (PNiPAAm) is synthesized by gamma radiation induced Reversible Addition–Fragmentation Chain Transfer (RAFT) polymerization. The monomer is polymerized in the presence of two different trithiocarbonate-based RAFT agents i.e., Cyanomethyldodecyltrithiocarbonate (CDTC) and 2-(Dodecylthiocarbonothioylthio)-2-methylpropionic acid (DMPA) in dimethylformamide (DMF) at room temperature under nitrogen atmosphere. Number-average molecular weights (Mn) and dispersities of the polymers were determined by Size Exclusion Chromatography (SEC). Dispersities (Ɖ) of the resulting polymers are narrow, i.e., Ɖ≤1.18, indicating the occurrence of well-controlled polymerization via radiation induced RAFT process. %Conversion is determined by gravimetric method and also confirmed by Proton Nuclear Magnetic Resonance (1H-NMR) Spectroscopy. By selecting proper [Monomer]/[RAFT] ratio and controlling conversion it is possible to synthesize PNiPAAm in the molecular weight range of 2400–72400 with extremely low molecular weight distributions with the anticipation of preparing corresponding size-controlled nanogels. The phase transition of PNiPAAm with low dispersity synthesized by RAFT is sharper than PNiPAAm synthesized by free radical polymerization.