Computer Simulation Study On Hierarchical Self-assembly Of Multiblock Copolymer Chain In Dilute Solution

We study the hierarchical self-assembly of multiblock copolymer viacoarse-grained molecular dynamics （CGMD） simulations. Well-defined patchynanoparticles are obtained by the self-assembly of single multiblock copolymerchain in solvent bad for both components. Three-dimensional network andbicontinuous membrane structures are observed for two-patch particles withdifferent cross-linking densities in selective solvent. We also study theself-assembly of an amphiphilic multiblock copolymer with different topologiesand observe the formation of flower-like, bridge, core-shell micelles, and so on.By using computer simulations, we propose a simple and rationalbottom-up method, which has great potential to overcome the size limitationsand processing restrictions of the current "top-down" processes, to fabricate7–17nm patchy particles via self-assembly of a multiblock copolymer in onestep by simply controlling the chain length and solvent properties. The patchyparticles possess controllable patch symmetries: We observe, such as one-patchparticle with C_∞v symmetry, two-patch particle with D_∞h symmetry,three-patch particle with D_3h symmetry, and four-patch particle with T_dsymmetry.The influence of deformability of patchy particles on their self-assemblybehavior is studied. The softness and the deformability of the patchy particlescan be controlled by varying the cross-linking densities in different parts of theparticles. The patchy particles in a solvent that is bad for patches but good forthe matrix form three-dimensional network structures at relatively highcross-linking densities, and form short thread-like structures for cross-linkingdensities are relatively low. For patchy particles in a solvent that is good forpatches but bad for the matrix, bicontinuous membrane structures are obtainedat relatively low cross-linking densities, and inter-connected clusters can be observed when cross-linking densities are relatively high.We study the influence of solvent condition and the chain backbonestiffness of amphiphilic multiblock copolymer with different topologies inselective solvent on their self-assembly structures. For linear chain, variousinteresting structures, such as flower micelles and bridge structures are observed.In general, stronger attractive interactions between hydrophobic beads arebenefit to form flower micelles, while semi-flexible chain is prone to formbridge structures, and high component ratio for the hydrophobic beads favorslarge structural region in phase diagram. A single to multiflower transitionhappens with increasing the chain length, while well-defined homogeneousmulticompartment wormlike micelles are obtained from the pre-assemblystructure of the flower micelles in solvent bad for both components. For graftedchain, core-shell micelles and bunchy-like structures can be observed when wechange the selectivity of the solvent.