Effect of skin-penetrating enhancers on the thermophysical properties of cholesteryl oleyl carbonate embedded in a thermo-responsive membrane

The effect of skin-penetrating enhancers such as propylene glycol (PG), Azo ne and ethanol on the thermophysical properties of cholesteryl oleyl carbon ate (COC) was investigated using differential scanning colorimetry (DSC) an d microscopic Fourier-transform infrared (FT-IR) spectroscopy. The results indicate that PG did not influence the DSC thermograms and IR spectra of CO C in the different ratios of COC and PG mixture; whereas Azone interacted w ith COC not only to lower the semectic-cholesteric phase transition tempera ture of COC but also to induce a new IR spectral peak at 1653 cm(-1) which shifted from the carbonyl stretching band (1636 cm(-1)) of Azone. Ethanol d id not interact with COC, but it influenced the IR spectral peak intensity of COC at 1253 cm(-1). The peak intensity at 1253 cm(-1) gradually rose wit h the time of ethanol evaporation and was similar to that of the temperatur e effect. The solubility parameter was also used to explain the miscibility and interaction between COC and PG, Azone or ethanol. (C) 2000 Kluwer Acad emic Publishers.