The effects of copolymer architecture on phase separation dynamics of immiscible homopolymer blends in the presence of copolymer: a Monte Carlo simulation

The effects of copolymer architecture on phase separation dynamics of an im miscible binary blend A/B in the presence of copolymer were investigated by Monte Carlo simulation. Five types of copolymers, with each having the sam e composition (f = 0.5) but different sequence distribution, are used for s imulation. The sequence distribution is varied from the symmetric diblock c opolymer to the alternating copolymer. It is found that the rate of phase s eparation is significantly suppressed by the addition of copolymer due to t he reduction of interfacial tension. This retardation effect is considerabl y dependent on the sequence distribution of the copolymer and such an effec t is more pronounced when the block copolymer is added. It is also found th at the longer the chain length of copolymer, the better such a retardation effect. When the chain extension of copolymer at the interface is examined, the block copolymer chains are extended to each corresponding homopolymer phase across the interface, whereas the alternating copolymers lie on the i nterface and the random copolymers weave back and forth across the interfac e. (C) 2000 Elsevier Science Ltd. All rights reserved.