Role of Water/Methanol Clustering Dynamics on Thermosensitivity of Poly(N-isopropylacrylamide) from Spectral and Calorimetric Insights

The role of water/methanol clustering dynamics on thermosensitivity of poly(N isopropylacryl amide) (PNIPAM) chains in concentrated solutions (10 wt %) is investigated by turbidity, FT IR and calorimetric measurements through point by point comparison FT IR spectral variations show that PNIPAM methanol interactions are largely weakened and PNIPAM chains are more collapsed in water/methanol mixture (methanol volume fraction x(m) = 0 17) than in pure water because of the formation of large water/methanol clusters which meanwhile causes the decrease of hydration sites On the other hand, weak hysteresis and excess recovery phenomena in the phase transition process can also be observed with addition of methanol to PNIPAM aqueous solution due to the existence of water/methanol clustering dynamics Two dimensional infrared correlation spectroscopy and calorimetric analysis finally conclude that the role of water/methanol clustering dynamics is mainly embodied in the inhibition of the hydration process of PNIPAM chains which shows a faster thermal response than hydrogen bonding association