Low-temperature calorimetry on molecular glasses and crystals

We have designed and developed a versatile calorimetric system especially intended for glass-forming liquids, with which we are able to concurrently study and characterize the phase transitions in the range 77-300 K and also to measure their specific heat at low temperatures (0.3-30 K). At the former, higher temperatures we employ either a continuous method or the quasi-adiabatic, Nernst method. For specific-heat measurements at lower temperatures, we can use both quasi-adiabatic and thermal-relaxation methods. In particular, we have built up two complementary versions of the thermal-relaxation method (the standard one and an alternative version useful for longer relaxation times). A user-friendly PC software has been developed, allowing us to choose among the four calorimetric methods, as well as to tune all controlling parameters. We have applied this experimental system to investigate the calorimetric and thermodynamic behavior of the different solid phases of ethanol, as well as other interesting glass-forming systems such as alkyl-cyclohexanes or ionic liquids. (C) 2007 Elsevier B.V. All rights reserved.