Coil‐to‐Globule Transition of Poly(<i>N</i>‐isopropylacrylamide) in Aqueous Solution: Kinetics in Bulk and Nanopores

Abstract

Differential scanning calorimetry (DSC) is used to study the kinetics of the coil‐to‐globule transition in aqueous solutions of poly( N ‐isopropoylacrylamide) (PNIPAM) prepared in the bulk (3 and 10 wt%) and nanoconfined (10 wt% inside 30 nm silica pores) forms. It is demonstrated that the kinetics can be described in terms of the classical nucleation model. The proposed treatment affords estimating the free‐energy barrier and pre‐exponential factor of the transition. The application of the nucleation model to the DSC data collected for the three systems studied provides physical insights into the effect of increasing the transition temperature due to dilution and nanoconfinement. Dilution appears to raise the free‐energy barrier, whereas nanoconfinement causes a decrease in the pre‐exponential factor. image