Hydration and Conformation of Temperature-Dependent Micellization of PEO−PPO−PEO Block Copolymers in Aqueous Solutions by FT-Raman

Abstract

The micellization of four triblock copolymers of the poly(ethylene oxide)x−poly(propylene oxide)y−poly(ethylene oxide)x type (Pluronic P103, P104, P105, and F88) in aqueous solutions versus temperature is followed by Fouier transform-(FT-) Raman spectroscopy. The frequencies and relative intensities of C−H stretching bands in FT-Raman spectra are sensitive to the local polarity and conformation of block copolymer chains, and their variations with temperature are indicators of micellization. Therefore, the critical micellization temperatures of these copolymers of 10% concentration in aqueous solutions are determined. The deconvolution method is used to resolve the overlapping bands in the C−H stretching region, and the deconvoluted spectra provide information about the structural and microenvironmental changes of ethylene oxide (EO) and propylene oxide (PO) blocks, respectively. The hydration of the EO chains in the corona is found to diminish with increasing temperature, and the conformation changes to a...