Monte Carlo binodals for the order–disorder transition in A-B-A copolymer melts

The ABA triblock copolymer melts are simple and illuminating prototypes for soft self-assembling systems because they exhibit a remarkable richness of nanostructures and useful molecular features, such as B-bridges connecting the neighboring A-nanodomains. The transition from disordered phase to ordered phase is of particular interest and therefore we determine binodals for the order–disorder transition (in terms of the thermodynamic incompatibility and the triblock asymmetry), using lattice Monte Carlo method, known as cooperative motion algorithm, and also employing the parallel tempering method which is known to be efficient at lower temperatures. The simulated binodals are presented as a 3-dimensional phase diagram and confronted with earlier mean-field (self-consistent field theory) calculations. While the Monte Carlo binodals show qualitatively similar trends to those observed in the mean-field calculations, there is a pronounced numerical difference between them which indicates the significant role of fluctuations in the vicinity of the order–disorder transition.