Cohesional Entanglement of Amorphous Polymer in Glass State as Probed by Equilibrium Swelling in a "Non-Solvent"

• 来源期刊: 中国化学(英文版)
• 年，卷（期）: 2002,（11）
• 页码范围: 1154-1161
• 页数: 8页
• 语种: 英文

摘要

The equilibrium swelling of the system Polystyrene (PS) (M=1.7× 105, monodisperse)/diethyl ether at30 ℃ and35 ℃ has been studied in detail in quiescent state for a time span over 150d. Arguments are given to show that the swellingg process in a "non-solvent" is a network swelling rather than a phase separation process. It is different from the cloud point curve (CPC)experiment studied in literature, where the experiment starts from a one-phase solution, so that the cohesional entanglement present in the solid polymer is disrupted by dissolution. The cohesional entanglement structure of the solid polymer, on the contrary, is retained in the concentrated phase on swelling, at least in the initial stage. The course of swelling as presented by the curve Vs(t) was found to proceed in three stages, where Vs is the volume of the concentratd phase. In the first and third stages of Vs(t), the curve goes up smoothly, while in the second stage the curve Vs( t ) shows large up and down jumps,indicating probably a readjustment in the network structure.Some results on a monodisperse PS sample of M = 5.8 × 105and a polydisperse sample of M = 2.0 × 105 are also given. The values of Vs observed at swelling equilibrium are not in accord with the expected cloud point temperature. The cloud point curve represents a phase separation process occurring in local regions (space limited to um) and in time scale of the order of mimute, while the process Vs( t ) occurred in the whole space of the concentrated phase, in time scale of days. For quantitative characterization of the network present in the concentrated phase, a precise value of the polymer- solvent interaction parameter χ is needed.