Micro-Raman investigations of pressure-induced transformations in MBBA

Abstract

The pressure-induced changes in the Raman spectra of a nematic N-(p-methoxybenzylidene)-p-(n-butyl)aniline (MBBA) liquid crystal were investigated in the wavenumber range 5-1670 cm-1. With increasing pressure, the Raman spectrum undergoes qualitative changes in a systematic manner and three distinct phase transitions, from nematic to plastic crystal, from plastic to crystalline and from to are obtained around 0.39, 0.78 and C 6P C 6P C 5P , 3.12 GPa, respectively. The room temperature results obtained in this pressure study provide information on the structural modiÐcations and phase behavior of MBBA molecules. The appearance of a plastic-like state was veriÐed just below the nematic phase. The e †ects of pressure variation on MBBA phonon modes are discussed in detail.