Dissolution behavior and solution properties of polyvinylalcohol as determined by viscometry and light scattering in DMSO, ethyleneglycol and water

As it is very difficult to obtain molecularly dispersed solutions of polyvinylalcohol (PVA) in water and as the properties of these solutions change on ageing due to the formation of aggregates, the dissolution behavior and solution properties of PVA with molar masses ranging from 15 to 690 kg/mol in two other solvents, dimethylsulfoxide (DMSO) and ethyleneglycol (EG) was investigated by continuously monitoring eta(sp)/c as a function of dissolution time using a simple Ubbelohde viscometer and light scattering. The optimum dissolution temperatures ranged from 60 to 120 degrees C. The solutions remain stable for at least 24 h. Even yarns which are virtually insoluble in water could successfully be dissolved in DMSO at 120 degrees C. The Huggins constant for PVA both in water and ethyleneglycol is 0.5 and 0.3 in DMSO. Filtration of the PVA solutions in DMSO caused no clogging of filters (0.2 mu m). From light scattering it became apparent that PVA is molecularly dispersed in DMSO and that the solutions show no aggregation and hence no ageing. For PVA in DMSO the second virial coefficient appeared to be 4-15 x 10(-4) cm(3) g(-2) mel. This may be compared to <2 x 10(-4) cm(3) g(-2) mol in water. The Mark-Houwink relations for PVA in DMSO at 65 degrees C ([eta] = 1.51 x 10(-4) M-w(0.804)), ethyleneglycol at 140 degrees C ([eta] = 3.54 x 10(-4) M-w(0.692)) and water at 30 degrees C ([eta] = 6.51 x 10(-4) M-w(0.628)), were established. These findings indicate that DMSO is a good solvent for PVA. (C) 1999 Elsevier Science Ltd. All rights reserved.