Phase Behaviour of Cyclo-octanol up to Pressures of 300 MPa and Temperatures between 100 and 370 K

Study of the nature of glass transitions in the plastic crystalline phases of cyclo-octanol, cycloheptanol, cyanoadamantane and cis-1,2-dimethylcyclohexane

“…To give some idea of the deviations of these transition temperatures from the data of others, we have also entered the corresponding values reported in the literature. 28,32,33,45 The deviation of the transition temperatures from the reported values are probably due to impurities present in our samples. The nature of the transition has been identified on the basis of the present dielectric work and the thermal study of others.…”

“…2͒. Interestingly, the corresponding DSC curves do not show any sign of a new phase which can be identified 28,29 with phase III of the high pressure side. In addition to the above results, the DSC runs on all samples with different sample histories revealed another small steplike change around 136 K for a heating rate of 10°/min.…”

“…The relaxation data either do not exist throughout the temperature range because of various problems including recrystallization 27 to the NC phase or are available only in a few systems without much supporting information from other techniques. Also in the case of cyclic alcohols, the transition temperatures are often sensitive to the amount of impurities 28 ͑probably because of the existence of various confirmers͒, which is further complicated by the existence of more than one PC phase ͑for the same reason 5 ͒ and hence, can exhibit more than two glassy crystalline transitions. 5 The glass transition temperature, in a general sense, can be defined as the temperature where the various physical properties exhibit a sharp change on cooling of a material.…”

Variation of ionic conductivity in a plastic-crystalline mixture

“…The final melting of the fully orientationally disordered PC phase occurs at T m = 293 K, in reasonable agreement with literature. 26,27,29,30 Pure HEX [Fig. 1(b)] displays a similar thermodynamic behavior with o g T  150 K. 38,39 In this compound, the region of cold crystallization and subsequent melting during heating is spread from 180 K to 250 K, a signature of the complex phase diagram of cyclohexanol.…”

“…The pure compounds were measured as received. Pure OCT forms a plastic-crystalline phase on cooling 26,27,28,29,30,31 revealed in the DSC trace by a slightly supercooled exothermic transition at about 280 K [Fig. 1(a), lower line].…”