Abstract
Thermotropic phase transitions of octadecyldimethylamine hydrochloride (OHC) and dioctadecylmethylamine hydrochloride (DOHC) -water systems were studied by fourier transform infrared spectroscopy. In the OHC system, coagel-gel and gel-liquid crystalline phase transitions occurred at 22 and 50°C, respectively. In the DOHC-water system, coagel and liquid crystalline states were confirmed present but not the gel state. In the coagel phase, methylene chains took on a trans-zigzag conformation with the hydrophilic part remaining in a fixed state. In the gel phase, rotational motion of the methylene chains about the chain axis was noted in the hexagonal lattice, and the hydrophilic part was in a fused state. In the liquid crystalline phase, hydrophobic and hydrophilic parts were in fused states.
