The study of liquid crystalline phases as an experimental procedure for chemistry education

The present study was an attempt to introduce an advanced subject in chemistry, liquid crystals, in a simple form which could be suitable for chemistry education in college. Liquid crystals have found a variety of applications in chemistry, physics and biology yet they are rarely, if at all, included in courses taught at the undergraduate or graduate levels.

The present study was concerned with phase behavior and phase formation in mixtures of dodecyl amine (-NH_/-ND_)/water and/or 2' After preparation the mixtures were heated until homogeneous solutions were obtained. Drops from these homogeneous solutions were placed on ordinary glass slides then covered by thin glass microscope cover slips. Slides of human nerve tissue and ovary tissue were obtained from The University of Tennessee Center for the Health Sciences. Dodecyl amine samples and tissue samples were studied using a Nikon polarizing microscope fitted with a 35mm camera. A thin hot plate fixed to the microscope stage was used to heat the samples so that the effect of temperature on the phase formation could be studied.

The dodecyl amine (Aldrich 98%) used during the course of this study was recrystallized twice from acetonitrile and then fractionally distilled two times in a rotating band column at l35°C and 15 torr. The melting point of the purified amine was found to be 28.3°C which is in good agreement with the most recent published data. The deuterated amine

several hours. The melting point of the deuterated amine was found to be 29.1°C.

The results of these investigations were presented in the form of colored photomicrographs. The effect of concentration variation on

was studied in detail. Also the effect of temperature on the phase behavior in the previously mentioned mixtures was qualitatively studied. A comparison between the structural appearance of the nerve tissue samples, ovary samples and dodecyl amine mixtures was conducted.

The results indicated the existence of two new liquid crystal phases which had not been reported in the literature. The first was a "threedimensional hexagonal crystal" "A" phase. This phase was anisotropic and composed of single crystals which had a layer arrangement parallel to each other. The results showed that this phase was stable at room temperature, over a period of eighteen months. The second phase was

anisotropic and composed of octagonal micelles which possessed a core. It was found that this "B" phase was similar to "A" phase regarding its polarizing ability.