Acta Chimica - Models in Chemistry 129. (1992)

5. szám - RESEARCH ARTICLES - Nagy M.–Györgyi-Edelényi Judit–Martinusz Kinga: Association-Aggregation Phenomena in Polymer Gels, III.

NAGY et al.: ASSOCIATION-AGGREGATION PHENOMENA IN POLYMER GELS, III 601 To certain extent similar behaviour was observed in solutions of block copolymers, but in some aspects the effects were significantly different (Fig. 14). The similarity holds for the shapes of the curves describing the dependence of swelling and limiting viscosity numbers on the composition of the mixtures. The difference is that above the «-propanol concentration (approximately 60 m/m%) corresponding to the initiation of structure formation the value of the limiting viscosity number begins to rise again. However, it should definitely be mentioned that the precise measurement of viscosity of systems that incline to gel formation or to phase separation was not a simple experimental task. On the side of water rich mixtures the viscosity measurements had to be limited to the regions shown in the figure because of fibre like polymer segregation; on the «-propanol rich side, in spite of the rather low Fig. 13. Comparison of the behaviours of gels and solutions, a - Dependence of the degree of volume swelling in poIy(vinyl alcohol, vinyl acetate) statistical copolymer gel of minimum degree of cross-linking on the mass fraction of л-propanol; b - Dependence of the limiting viscosity number and of the k’ constant in linear poly(vinyl alcohol, vinyl acetate) copolymer (Sjg) on the composition of the mixture Acta Chimica Hungarica - MODELS IN CHEMISTRY 129, 1992

Next