Effects of Compositional Asymmetry in Phase Behavior of ABA Triblock Copolymer Melts from Monte Carlo Simulation
S. Wołoszczuk1 , M. Banaszak1
1 Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614, Poznan, Poland
The European Physical Journal E, 33 (04), 343-350 (2010)
We simulate ABA triblock copolymer melts using a lattice Monte Carlo method, known as cooperative motion algorithm, probing various degrees of compositional asymmetry. Selected order-disorder transition lines are determined in terms of the segment incompatibility, quantified by product χN, and the triblock asymmetry parameters, α and β. We correlate the results of the simulation with the self-consistent field theory and an experimental study of polyisoprene-polystyrene-polyisoprene triblock melt by Hamersky and coworkers. In particular, we confirm the mean-field prediction that for highly asymmetric triblocks the short A-block is localized in the middle of the B-domain due to an entropic advantage. This results in the middle block relaxation and is consistent with the experimental data indicating that as the relatively short A-blocks are grown into AB diblock, from the B-block side, the order-disorder transition temperature is considerably depressed.