Search

The interactions between Carbopol and β-cyclodextrin (BCD) or hydroxypropyl-β-cyclodextrin (HPBCD) were studied by differential scanning calorimetry (DSC) and FTIR spectroscopy. Aqueous solutions of both components were desiccated by freeze-drying or heating in an oven (films) at various temperatures. The use of different drying procedures allowed their influence on the interactions to be studied. The evolution of the Carbopol glass-transition was also evaluated by DSC using first heating runs up to different temperatures. Disappearance of the Carbopol glass-transition was observed in the freeze-dried systems prepared with either of the cyclodextrins and in the films that contained HPBCD. The changes in the FTIR band of Carbopol at 1700 cm-1 confirmed the existence of interactions with both cyclodextrins, especially with HPBCD. This information may be useful for optimising the solubilizing capacity and controlled release performance of aqueous Carbopol-cyclodextrin systems. [ABSTRACT FROM AUTHOR]

Besides a short introduction to historical data on inorganic and polymeric glasses, some aspects of the glassy-state are analyzed: particularly, induced entropy changes, characteristics of the glass transformation and a novel anharmonicity vibrational approach. The horizons and scientific prospects for the nano- and non-crystalline states are discussed. [ABSTRACT FROM AUTHOR]

Temperature-modulated differential scanning calorimetry (TMDSC) has recently been introduced as a promising calorimetric technique. However, the added value of TMDSC in practice is still not very obvious, in particular with respect to crystallization and melting. An important reason is that the evaluation is less transparent than in case of other dynamic techniques since in TMDSC the response is also based on temperature. Moreover, the temperature program applied is very critical. In this paper an overview is given of the different aspects of TMDSC using a general theoretical description based on the full heat capacity formulation. It is demonstrated that processes studied with the aid of TMDSC can simply be classified into three distinct regimes, depending on the time scale and the susceptibility of the process to the temperature modulation. [ABSTRACT FROM AUTHOR]