Micro- and mesoscopic structure of poly(vinyl alcohol) gels determined by neutron and light scattering

We studied the structure of poly(vinyl alcohol) (PVA) gels formed in mixtur es of dimethyl sulfoxide (DMSO) and water using several scattering techniqu es such as wide-angle neutron scattering (WANS), small-angle neutron scatte ring (SANS), ultra-small-angle neutron scattering (U-SANS) and light scatte ring (LS) to cover a very wide Q range from 10(-4) to 10 Angstrom(-1). The WANS measurements have revealed that the cross-linking points of the gels a re crystallites, and the size and its distribution have been evaluated by t he SANS measurements. The SANS results have also shown that the structure o bserved in the low Q range below 10(-2) Angstrom(-1) is dominated by a liqu id-liquid-phase separation. The early stage of the phase separation has bee n studied in detail using the time-resolved LS technique, while the late st age has been investigated by the U-SANS technique because the LS measuremen ts cannot access the opaque samples. On the basis of the results, we presen t a quantitative sketch of the structure of the PVA gel. (C) 1998 Elsevier Science Limited. All rights reserved.