Thermodynamic, crystallographic, and dielectric study of the nature of glass transitions in cyclo-octanol

Abstract

The stable solid polymorphism of cyclooctanol $({\mathrm{C}}_{8}{\mathrm{H}}_{16}\mathrm{O},$ for short ${\mathrm{C}}_{8}--\mathrm{OH})$ is revealed to be a complex problem and only two stable solid phases, denoted on cooling from the liquid as phases I and II, are found using static (thermodynamic and x-ray diffraction) as well as dynamic (dielectric spectroscopy) experimental techniques. Both solid phases are known to exhibit glass transitions if they are cooled down fast enough to prevent transition to ordered crystalline states. Although glass transitions corresponding to both phases had been well documented by means of specific heat measurements, x-ray measurements constitute, as far as we know, the first evidence from the structural point of view. In addition, a great amount of dielectric works devoted to phase I and its glass transition, were published in the past but next to nothing relating to the dielectric properties of phase II and its glass transition. The nature of the disorder of phase II will be discussed.