Graduate Student Oral Presentation 3
Sorption and Diffusion of Water in Polystyrene-Poly(ethylene oxide)
Block Copolymers
Onyekachi Oparaji and Daniel Hallinan Jr.
Department of Chemical and Biomedical Engineering, FAMU-FSU, COE
Poly(styrene-block-ethylene oxide) (PS–b–PEO) is a model hierarchically nanostructured polymer for a water sorption and
diffusion study. Amphiphilic block copolymers such as PS–b–PEO are of interest for a wide-range of applications, but accurate
measurement of water transport is needed to determine the appropriate application(s) for this material. PEO crystallinity and block
copolymer structure were measured as a function of water activity. They were found to change appreciably at high water activity.
Gravimetric water sorption and transport were also measured over a range of water vapor activity (0.05 – 0.95). Due to the structural
changes in the polymer, water sorption was found to increase exponentially at high water activity. Water diffusion was measured
using Fourier transform infrared – attenuated total reflectance (FTIR-ATR) spectroscopy. The water content and diffusion in PS–b–
PEO was compared to a poly(ethylene oxide) (PEO) homopolymer. The interplay of water content and PEO crystallinity resulted in
interesting transport results. The crystalline content of the PEO and the presence of glassy PS lamellae will be used to explain the
transport results
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