Eur. Phys. J. E (2011) 34: 43
https://doi.org/10.1140/epje/i2011-11043-6

Selectivity and temperature dependence of phase and phase transition in diblock copolymer solution

Key Laboratory of Soft Matter Physics, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China

^* e-mail: lyzhang@iphy.ac.cn

Received: 31 July 2010
Accepted: 28 March 2011
Published online: 21 April 2011

Abstract

In order to study the effects of solvent selectivity and temperature on phase behavior and transition of diblock copolymer solution, self-consistent field theory is modified to incorporate the short-range interaction and non-local effects. Inhomogeneous free-energy density is shown to be dependent on solvent selectivity, temperature and copolymer concentration. Enthalpic quantity and entropic contributions are crucial to phase diagrams of diblock copolymer solution. Three selective strengths of solvent --weak, moderate and strong-- are chosen for comparison. For a weakly selective solvent, theoretical and experimental results illustrate the same variation tendency in the phase boundary of the order-disorder transition for a symmetric diblock of polystyrene and polyisoprene. Self-consistent field equations can be used to calculate the exact FCC-BCC structural phase transition temperatures in moderately and strongly selective solvents. Detailed comparison with the experimental phase diagrams including lamellar, cylindrical and spherical structures is presented.