Dissipative Particle Dynamics Simulations Of The Self-assembly Of Block Copolymer In Melts Dan Solution

The block copolymers may self-assemble into the novel andlong-range order materials in nano-scale, which plays important roles onthe study of preparation of polymer technology, biological medicine, andphotonic crystal in recent years. This report uses dissipative particledynamics (DPD) simulation method to study the phase behaviors of blockcopolymer with different architectures and solvent conditions. Firstly weinvestigate the self-assembly of diblock copolymer(AmBn) in melts and inselective solutions，and discuss the different self-assembly induced by themolecular topological structure. Secondly, we study the phase behavior oflinear rod-coil copolymer(l Rm C n) in coil-selective or rod-selectivesolutions.In first part, we study the self-assembly of cyclic and linear diblockcopolymer in melts，and the phase behaviors are compared systematically.We consider the factors that influence the self-assembly behavior ofsystem, such as the repulsive interactions between block A and B, and Ablock ratio in diblock copolymer. we obtain the phase diagram ofcopolymer nanostructures in terms of these two parameters: disorder,spherical, cylindrical, and lamellar. It can be concluded that chaintopology and conformation entropy dominate the self assembly of system.Furthermore, we observe the order-disorder transition of cyclic and linear diblock copolymers, and compare cylindrical or lamellar period size fromcyclic and linear diblock copolymers, respectively. We find that the phaseperiod size of linearl Am Bnis larger than that of cyclicc Am Bn.In second part, we study the self-assembly of cyclic and lineardiblock copolymer in B selective solutions. We explore the effects ofcopolymer concentration, the repulsive interactions, B block ratio indiblock copolymer, and the polymerization degree of copolymer on theself-assembly behavior ofAmBnsolutions. We observe that inducedcommonly by microphase separation and chain conformation entropy,linear and cyclic copolymers in selective solutions take place a series ofmorphological transitions, including spherical, hollow cylindrical, sheet,hollow spherical, and disc phases.Finally, we study the self-assembly of linear rod-coil diblockcopolymer in coil-selective or rod-selective solvent. With varying rodlength and chain length, some diverse morphologies are observed,including micelle, hollow spherical, rod bundle, and liquid crystal discphases. These rich morphologies are formed depending on the interplaysbetween rod orientation, chain free energy, polymer concentration,interaction strength between bloc rod and coil, and solvent selectivity.Furthermore, we observe the rod orientation and distribution in bundlephase in detail.