From measurements of the specific volume as a function of temperature and pressure, the phase diagram for the liquid crystal forming isopentylcyanobiphenyl (5*CB) was determined. There are a number of phases (isotropic liquid, glass, cholesteric, and crystalline), and we show that the phase boundaries differ from previous reports, reflecting the slow crystallization kinetics of the system. Using dielectric spectroscopy at ambient and elevated pressure, we identify the relaxation processes in ...
Dielectric relaxation times were measured for 1,4-polyisoprenes (PI) of different molecular weight. From the data, the number of dynamically correlated segments, Nc, was calculated using an approximation to the dynamic susceptibility. Nc increases with approach to the glass transition in the usual fashion and also increases with increasing molecular weight of the PI. The latter effect is ascribed to the loss of the configurational mobility conferred by the chain ends. ...
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