Phase diagrams for monodisperse and polydisperse diblock copolymer melts and a random multiblock copolymer melt are constructed using dissipative particle dynamics simulations. A thorough visual analysis and calculation of the static structure factor in several hundreds of points at each of the diagrams prove the ability of mesoscopic molecular dynamics to predict the phase behavior of polymer systems as effectively as the self-consistent field-theory and Monte Carlo simulations do. It is demonstrated that the order-disorder transition (ODT) curve for monodisperse diblocks can be precisely located by a spike in the dependence of the mean square pressure fluctuation on χN, where χ is the Flory-Huggins parameter and N is the chain length. For two other copolymer types, the continuous ODTs are observed. Large polydispersity of both blocks obeying the Flory distribution in length does not shift the ODT curve but considerably narrows the domains of the cylindrical and lamellar phases partially replacing them with the wormlike micelle and perforated lamellar phases, respectively. Instead of the pure 3d-bicontinuous phase in monodisperse diblocks, which could be identified as the gyroid, a coexistence of the 3d phase and cylindrical micelles is detected in polydisperse diblocks. The lamellar domain spacing D in monodisperse diblocks follows the strong-segregation theory prediction, D∕N(1∕2) ~ (χN)(1∕6), whereas in polydisperse diblocks it is almost independent of χN at χN < 100. Completely random multiblock copolymers cannot form ordered microstructures other than lamellas at any composition.

End-coupling between immiscible melts of two monofunctionalized polymers of a same length was modeled by dissipative particle dynamics starting from a flat interface and up to the formation of a mature lamellar microstructure. Influence of the reaction rate, chain length, and incompatibility of components on the kinetics of copolymer formation and morphology development was investigated. Regimes of linear and logarithmic growth of the conversion with time were observed before the flat interface became unstable. The conditions and mechanism of interfacial roughness development were studied in detail. It was demonstrated that overcrowding the interface with the copolymer product causing its phase separation plays the main role in spontaneous interface distortion. The instability leads to autocatalytic interface growth with exponential kinetics, when each new portion of the product creates more area for further reactions. It was followed by a slower terminal regime including formation and ripening of the lamellar microstructure. The late stage kinetics of end-coupling was strongly influenced by depletion of reactants and formation of ordered product layers. At certain conditions, it became asymptotically diffusion controlled in agreement with published experimental data.

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Short title: Ordering of anisotropic nanoparticles: Simulations and theory a) Corresponding author. Electronic mail: yar@ips.ac.ru 2 ABSTRACT Local distribution and orientation of anisotropic nanoparticles in microphase-separated symmetric diblock copolymers has been simulated using dissipative particle dynamics and analyzed with a molecular theory. It has been demonstrated that nanoparticles are characterized by a non-trivial orientational ordering in the lamellar phase due to their anisotropic interactions with isotropic monomer units. In the simulations, the maximum concentration and degree of ordering are attained for nonselective nanorods near the domain boundary. In this case the nanorods have a certain tendency to align parallel to the interface in the boundary region and perpendicular to it inside the domains. Similar orientation ordering of spherical nanoparticles located at the lamellar interface is predicted by the molecular theory which takes into account that the nanoparticles interact with monomer units via both isotropic and anisotropic potentials. Computer simulations enable one to study the effects of the nanorod concentration, length, stiffness, and selectivity of their interactions with the copolymer components on the phase stability and orientational order of nanoparticles. If the volume fraction of the nanorods is lower than 0.1, they have no effect on the copolymer transition from the disordered state into a lamellar microstructure. Increasing nanorod concentration or nanorod length results in clustering of the nanorods and eventually leads to a macrophase separation, whereas the copolymer preserves its lamellar morphology. Segregated nanorods of length close to the width of the diblock copolymer domains are stacked side by side into smectic layers that fill domain space. Thus, spontaneous organization and orientation of nanorods leads to a spatial modulation of anisotropic composite properties creating an opportunity to align block copolymers by external fields which may be important for various applications.

Irreversible coupling between immiscible melts of two functionalized macromonomers A and B of different lengths resulting in the formation of a linear or graft block copolymer AB was modeled by dissipative particle dynamics. Recently (Macromolecules201144112), we investigated the mechanism of the instability caused by saturating an A/B interface with the copolymer product, which leads to a microdomain structure formation. The present simulations were focused on the influence of copolymer composition and architecture on the microstructure development and characteristics of different kinetic regimes. Nearly symmetric copolymers form bicontinuous microdomains facilitating mass transfer and resulting in the exponential coupling kinetics. Strongly asymmetric copolymers promote fragmentation of a minor phase into isolated domains hardly accessible for the remaining reactants so that the linear or even slower kinetics is observed. At an equal concentration of functional groups, grafting proceeds always slower than end-coupling since branched copolymers form less penetrable brushes at the interface than linear diblocks. The most effective screening is achieved with symmetric copolymers. Both end-coupling and grafting produce long-lived nonuniform microstructures, with the size and shape of domains monotonously changing along the distance from the initial A/B interface. In the interface vicinity, minor phase micelles can form ordered layers.