Raman spectroscopic study on water in aqueous solutions of temperature‐responsive polymers: Poly(N‐isopropylacrylamide) and poly[N‐(3‐ethoxypropyl)acrylamide]

A Raman spectroscopic study on property changes of water in the course of a temperatureresponsive solution‐aggregate transition phenomenon of aqueous poly( N ‐isopropylacrylamide) and poly[ N ‐(3‐ethoxypropyl)acrylamide] solutions was carried out. Upon the transition of polymers from coil to globule followed by the aggregation of individual polymer chains, the height ratio of the the peaks at 3250 and 3 400 cm −1 , corresponding to the OH stretching of water molecules, was drastically changed. Contribution of small water domains included in polymer aggregates (so‐called interstitial water) to the change in the Raman spectra was suggested. Effects of polymer concentration and molecular weight of polymers on the spectra were also examined.