A series of high molecular weight poly(N-isopropylacrylamide) (PNIPAM)s with low polydispersity (M(n) = 7.0 x 10(4) to 10.2 x 10(4) 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 (T(g)) of this high molecular weight isotactic PNIPAM series and the low molecular weight PNIPAM series (M(n) = 3.5 x 10(4) to 4.0 x 10(4) 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 T(g) of PNIPAM decreases with increase in its meso diad content (m %) and decrease in its molecular weight.