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Phase Transitions in p-(Phenyl Benzylidene)-p

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Phase Transitions in p-(Phenyl Benzylidene)-p

1

-Alkylaniline Compounds:

A Dilatometric Study

Chintalapati Srinivasua, Venkata G. K. M. Pisipatib, Chadalavada R. Prabhuc, Piratla Narayana Murtyd, and Somayajula Lakshiminarayanae

aDepartment of Physics, Andhra Layola College, Vijayawada-521 008, India

bS. S. D. Polymers, Plot No. C-4, APIE, Machilipatnam, India

cFaculty of Physics, Department of Applied Sciences, Higher College of Technology, P. O. Box 74, Al-Khwair-133, Muscat, Oman

dDepartment of Physics, Acharya Nagarjuna University, Nagarjunanagar-522 510, India

eUniversity Scientific Instrumentation Centre, Acharya Nagarjuna University, Nagarjunanagar-522 510, India

Reprint requests to V. G. K. M. P.; E-mail: venkata pisipati@hotmail.com Z. Naturforsch.62a,75 – 83 (2007); received November 6, 2006

Dilatometric studies are carried out on liquid crystals (LCs), viz., p-(phenyl benzylidene)-p1- alkylanilines (PBnA forn=7 – 10, 12, 14 and 16). LC PBnA compounds are found to exhibit four different types of phase variants. The lower homologues (forn=3 – 6) exhibit an NBE trivariant, intermediate homologues (with n=7 – 9) exhibit an NABE tetravariant, higher homologues (for n=10 – 12) exhibit an ABE tetravariant, and long higher homologues (forn=14 and 16) exhibit an AB bivariant phase sequence. Dilatometry studies in PBnA compounds infer the first order nature for IN (forn=7, 8 and 9), IA (forn=10, 12, 14 and 16), NA (forn=8 and 9) and AB (forn=14 and 16) phase transitions. Phase transitions involving the growth of the 3D smectic-B phase in PBnAs are found to be tuned by squeezing of orientational disorder. A comparative study of phase transitions exhibited by PBnA compounds is presented along with the data in other Schiff base compounds.

Key words:Phase Transitions; Dilatometry; Nematic and Smectic Phases; Orientational Disorder.

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