1 H NMR study of phase transition of uncharged and negatively charged poly( N ‐isopropylmethacrylamide) in D 2 O solutions

1 H NMR spectroscopy has been applied to the analysis of dynamic‐structural changes during temperature‐induced phase transition of non‐ionized poly( N ‐isopropylmethacrylamide) (PIPMAm) and ionized copolymers of N ‐isopropylmethacrylamide with sodium methacrylate, all in D 2 O solutions with various polymer concentrations ( c = 0.1‐10 wt.‐%) and ionic comonomer mole fractions ( i = 0‐10 mole %). It was found that the formation of compact globular‐like structures during the phase transition is independent of polymer concentration for non‐ionized samples; the presence of negative charges on the polymer chains leads to a dependence of the phase transition temperature on c and i . Virtually all PIPMAm segments are in globular‐like structures for low polymer concentrations; for c ⩾ 1 wt.‐%, this holds only for low content i of the ionic comonomer. An increase in c and i leads to a decrease in the fraction of polymer segments in globular‐like structures; for samples with highest values of c and i , the phase transition was not observed.