NMR STUDIES OF ENTANGLED POLYBUTADIENE NETWORKS, POLYMER CRYSTALLIZATION AT HIGH PRESSURE, AND KAOLINITE-WATER SYSTEMS AT HIGH PRESSURE.

摘要

Proton spin-spin relaxation studies are used on well-characterized peroxide-crosslinked polybutadiene networks to show the presence of free and trapped entanglements. These observations and the results of stress-relaxation measurements are discussed in terms of the Mooney-Rivlin equation; the effect of entanglements upon the 2C(,2) term is shown.;The dynamic structure of water on the surface of kaolinite is studied through high-pressure proton and deuterium NMR. These studies indicate a water layer of two to three molecules thickness bound to the surface. Extensive disruption of the hydrogen bond network in water is shown.;A new technique for measuring the kinetics of polymer crystallization at high pressure is shown to accurately indicate the development of crystallinity. The strengths of the technique over earlier methods are discussed and future experiments considered. Crystallization of polyethylene at high pressure is shown to have led to the formation of extended chain crystals with formation directly from the melt. Crystallization proceeds by homogeneous nucleation with interface control over the growth. A decrease in the surface energy of nucleation with increasing pressure is indicated.