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Pressure phase transition; dipalmitoyllecithin; lipid bilayer; gel; liquid crystalline

Dipalmitoyllecithin (DPL) shows an order ← → disorder pressure transition which is neither of first order nor of second order but can be treated as a fractional order (3/2 order) transition. The Ising model formalism is adopted for the study of such a system. A suitable equilibrium constant is defined which generates a 3/2 order transition. Transition curves are obtained and compared with the experimental curves of Liu and Kay. Reverse transition curves are also obtained and the system exhibits hysteresis effect. An approximate expression connecting transition pressures at different temperatures is obtained and the calculated and the experimental values are in good agreement.

R C Agnihotri¹ C Mehrotra¹ V D Gupta¹ Vandana Srivastava¹

1. Department of Physics, Lucknow University, Lucknow - 226 007, India

Published

July 1982

Manuscript received

15 December 1981

Manuscript revised

30 April 1982