Gelation of Polymer Solution and Percolation Model

点击翻译按钮获取中文摘要

This project was planned to study the validity of percolation model from the viewpoint that the gelation of polymer solution can be understood unifiedly together with the dynamics of phase transition or phase separation. We carried out the study of tracing to gelation of polymer solution and chracterization of growing clusters, characterization of polymer molecules the gel of which exhibits unique phase behavior, and polydispersity effect to phase transition. We used light scattering mainly and analyzed the decay rate distribution of the correlation functions. In order to evluate the degree of reaction quantitatively, radiation-induced polymerization and gelation system was also studied. For polysaccharide where gelation occurs at very dilute condition, anomaly was detected in cluster intensity and size, and it was shown to obey the power-law. For radiation-induced gel, it was difficult to determine the gelation point accurately. Correlation function shows power-law behavior at the gelation point, and the exponents for polysaccharide and radiation-induced gel were about 0.6-0.7 showing a big difference from the chemical gel. There exists a qualitative difference between physical and chemical gel. It was ascertained that the extent of nonergodicity is correlated strongly with the gelation. Interesting phenomena for the coupling between the phase separation (uncleation-growth) and the gelation was observed. For the polymers which exhibit sol-gel transition and volume phase transition, molecular characterization was carried out and the bases at the molecular level for such unique phase behavior were obtained. Especially, the origin of discontinuous volume phase transition was clarified.