Structure and dynamics of poly(vinyl alcohol) gels in mixtures of dimethyl sulfoxide and water

Abstract

We reviewed our structure studies on poly(vinyl alcohol) (PVA) gels formed in the mixtures of dimethyl sulfoxide (DMSO) and water using various scattering methods, including wide-, small- and ultra-small-angle neutron scattering and light scattering. These studies revealed the hierarchic structure of PVA gels formed in DMSO/water (60/40 v/v) in a very wide spatial scale from 1 Å to several micrometers. The crosslinking points are crystallites with radii of ∼70 Å, the distance between the neighboring crystallites is 180–200 Å, and the bicontinuous structure due to liquid–liquid phase separation is in μm scale. We also review our dynamic studies on three kinds of PVA gels at the nanometer scale using neutron spin echo techniques to separate the concentration fluctuations observed by small-angle neutron scattering into the static and dynamics contributions. Structure studies were performed on PVA gels in mixtures of dimethyl sulfoxide (DMSO) and water using various scattering methods to see the hierarchic structure. It was found that the crosslinking points are crystallites, the nearest-neighboring distance is 180–200 Å and the bicontinuous structure due to phase separation is in μm scale for the gel in DMSO/water (60/40). Dynamics of three kinds of PVA gels were also studied in nm scale using neutron spin echo technique.