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ABSTRACT
A novel chalconyl liquid crystalline (LC) homologous series with two phenyl rings and one central bridge RO−C6H4−CH=CH–CO−C6H4(O−C18H37) (meta) has been synthesized and studied with a view to understanding and establishing the effects of molecular structure on thermotropic LC behaviors or properties. Homologous series of present investigation (C1–C18) consists of thirteen homologues, and thermotropic mesomorphism for nematic and smectic commences from C3 and C6 homologues respectively. The C3, C4, and C5 homologues are enantiotropically nematic, whereas, the homologues from C6 to C18 are monotropically smectic plus nematic. Melting points and transition temperatures were determined using a polarizing optical microscope (POM) equipped with a heating stage. The textures of the nematic phase are threaded or Schlieren and that of a smectic phase are fan shaped of smectic-A or smectic-C type. The Cr−I/M, N−I/I−N, and N-Sm transition curves behave in the normal manner, and the Cr-I/M exhibits an odd-even effect. Analytical, thermal, and spectral data confirm the molecular structures. Thermal stabilities of smectic and nematic are low. Mesophase lengths are very short, ranging between 1–8°C and 14°C. The novel compounds are compared with a known series.
Acknowledgments
Authors acknowledge thanks to Dr. R.R. Shah, principal and management of K. K. Shah Jarodwala Maninagar Science College, Ahmedabad. Authors are also thankful to Dr. A.V. Doshi, Ex-principal of M.V.M. Science and Home Sci. College-Rajkot for his constant support, inspirations, help, and valuable comments and suggestions, as and when needed during the course of present investigation. Authors also thank NFDD Centre for the spectral and analytical services.