Effects of tacticity and molecular weight of poly(N -isopropylacrylamide) on its glass transition temperature

Abstract

A series of high molecular weight poly(N-isopropylacrylamide) (PNIPAM)s with low polydispersity (Mn = 7.0 × - 104 to 10.2× - 104 g mol-1, PDI = 1.23-1.35) having different isotacticity [meso diad (m) = 47-88%]] was successfully synthesized using the reversible addition-fragmentation chain transfer (RAFT) polymerization method in the presence of different concentrations of Y(OTf)3 Lewis acid. Measurement of the glass transition temperature (Tg) of this high molecular weight isotactic PNIPAM series and the low molecular weight PNIPAM series (Mn = 3.5 × - 104 to 4.0 × - 104 g mol-1, PDI = 1.2-1.3) having different isotacticity [meso diad (m) = 45-72%)] reported earlier by us (Ray et al. Polym. J. 2005, 37, 234) showed that Tg of PNIPAM decreases with increase in its meso diad content (m %) and decrease in its molecular weight. © 2011 American Chemical Society.