ABSTRACT
Transkarbam 12 (T12), the carbamic acid salt of omega-aminocaproic acid dodecyl ester, is a recently synthesized substance, whose high permeation enhancing activity through the human skin was found for certain drugs. In this work, the thermotropic phase behaviour of T12 has been studied by means of various techniques, namely, DSC, FTIR and FT-Raman spectroscopy, X-ray powder diffraction, and DRS. The temperature development of the X-ray reflections as well as of the conformationally sensitive Raman bands and the IR bands have been observed. At room temperature, the hydrocarbon chains of T12 exhibit a highly ordered structure, arranged in an orthorhombic perpendicular subcell. On heating, two transitions occur at 54 and at 66 degrees C. The first transition is related to the disruption of the carbamate structure and changes in the polar head group. The other transition represents the melting of hydrocarbon chains and the subsequent release of carbon dioxide. The time required for the rebinding of carbon dioxide and the reformation of the carbamate structure is dependent upon numerous factors and it was not possible to precisely determine the length of this process.
Subject(s)
Aminocaproates , Aminocaproic Acid/chemistry , Carbamates/chemistry , Calorimetry, Differential Scanning , Dodecanol/chemistry , Humans , Spectroscopy, Fourier Transform Infrared/methods , Spectrum Analysis/methods , Spectrum Analysis, Raman/methods , Temperature , X-Ray DiffractionABSTRACT
The thermotropic phase behaviour of the ceramide N-octadecanoylphytosphingosine (CER3) was investigated using differential scanning calorimetry, X-ray powder diffraction and FT-IR spectroscopy. CER3 was shown to be a polymorphic substance depending on the crystallisation conditions. Three different solid states were found. The FT-IR results elucidate changes in the hydrogen bonding interactions of the ceramide head group. It was shown that the amide I and the amide II vibration bands are quite sensitive to the phase transitions of CER. There are clear shifts in the band positions of those bands passing the phase transitions. Furthermore, changes were observed in the NH- and OH- stretching region. The study shows that there are strong inter- and intramolecular hydrogen bonds between hydroxy groups in the ceramide head group. There are also strong hydrogen bonds to the amide oxygen as shown by the band positions of the amide vibrations. The H-bonding network and conformation of the head group of CER3 alters due to the phase transitions.
