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Phase behavior of AB-multiblock copolymer melts which consists of chains with Laser distribution of A and B blocks have been investigated in the framework of the mean-field theory, where the polydispersity of copolymer is a function of two parameters K and M. The influence of the Laser distribution on higher order correlation functions (up to sixth order) are computed for various values of K and M, and their contributions on the phase diagrams and phase coexistence are presented. It is shown that, with increasing polydispersity (decreasing K and increasing M) the transition lines of all phases shift upwards, consequently polydispersity destabilize the system.
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