The effect of silica nanoparticles on the morphology of (10/90 wt%) PDMS/PBD blends during the shear induced coalescence of droplets of the minor phase at low shear rate was investigated systematically in situ by using an optical shear technique. Two blending procedures were used: silica nanoparticles were introduced to the blends by pre-blending silica particles first in PDMS dispersed phase (procedure 1) or in PBD matrix phase (procedure 2). Bimodal or unimodal droplet size distributions were observed for the filled blends during coalescence, which depend not so much on the surface characteristics of silica but mainly on blending procedure. For pure (10/90 wt%) PDMS/PBD blend, the droplet size distribution exhibits bimodality during the early coalescence. When silica nanoparticles (hydrophobic and hydrophilic) were added to the blends with procedure 1, bimodal droplet size distributions disappear and unimodal droplet size distributions can be maintained during coalescence; the shape of the different peaks is invariably Gaussian. Simultaneously, coalescence of the PDMS droplets was suppressed efficiently by the silica nanoparticles. It was proposed that with this blending procedure the nanoparticles should be mainly kinetically trapped at the interface or in the PDMS dispersed phase, which provides an efficient steric barrier against coalescence of the PDMS dispersed phase. However, bimodal droplet size distributions in the early stage of coalescence still occur when incorporating silica nanoparticles into the blends with procedure 2, and then coalescence of the PDMS droplets cannot be suppressed efficiently by the silica nanoparticles. It was proposed that with this blending protocol the nanoparticles should be mainly located in the PBD matrix phase, which leads to an inefficient steric barrier against coalescence of the PDMS dispersed phase; thus the morphology evolution in these filled blends is similar to that in pure blend and bimodal droplet size distributions can be observed during the early coalescence. These results imply that exploiting non-equilibrium processes by varying preparation protocol may provide an elegant route to regulate the temporal morphology of the filled blends during coalescence.

We study the influence of solvent conditions and the chain backbone stiffness of an amphiphilic multiblock copolymer on its self-assembly structures in dilute solution with Brownian dynamics simulations. Various interesting structures, such as single-flower micelle, multi-flower micelle, and single or multi-bridge structures, are observed. In general, highly hydrophobic components benefit the formation of flower micelle structures, while semi-flexible chains are prone to forming bridge structures. We also study the influence of the ratio between hydrophobic and hydrophilic components on self-assembly structures. From our phase diagram, we find that a high component ratio for the hydrophobic blocks favors the formation of micelles with various structural patterns. A single to multi-flower transition is observed by increasing the chain length of the multiblock copolymer. Well-defined multicompartment wormlike micelles can be obtained from pre-assembled flower micelles in a solvent that is poor for both components.

We present a mesoscale simulation model that is suitable for describing the deformable and non-centrosymmetric characteristics of soft triblock Janus particles. The model parameters are readily mapped onto experimental systems under different ambient conditions. We examine the influence of Janus balance and the flexibility of Janus particle aggregates on the packing structures. Some ordered structures, such as the hexagonal columnar structure and the body-centered tetragonal structure, are observed in our simulations. Our study demonstrates that the Janus balance and the flexibility of Janus particle aggregates can be tuned to obtain various ordered packing structures. The soft Janus particles with soft and deformable characteristics may bring new excitement to materials science.

We study living polymerization initiated from concave surfaces. We clarify that, depending on different criteria for ceasing the reaction, different relationships between grafted chain polydispersity index and the grafting surface curvature can be categorized. The average molecular weight of the grafted chains monotonically decreases as the grafting surface curvature increases. These results shed light on better control and design of functional porous materials for use in bioimplanting or chemical sensors.

The influence of deformability of two-patch particles on their self-assembly behavior is studied via computer simulations. The softness and the deformability of the patchy particles can be controlled by varying the cross-linking densities in different parts of the particles. The patchy particles in a solvent that is bad for patches but good for the matrix form linear thread-like structures when cross-linking densities are low, whereas they form three-dimensional network structures at relatively high cross-linking densities. For patchy particles in a solvent that is good for patches but bad for the matrix, inter-connected membrane structures are obtained at relatively low cross-linking densities, and some cluster structures emerge when cross-linking densities are high. Bicontinuous membranes with better morphologies can be observed by tuning the cross-linking densities of different parts of the patchy particles.

Janus particles exhibit interesting self-assembly behavior and functional performances. In particular, soft and deformable Janus particles, as diverse as Janus micelles, Janus microgels, and Janus dendrimers, should receive more attention due to their unique chemical and physical properties and enormous potential applications. Gaining control over precise and predictable self-assembled structures and understanding the fundamental details of self-assembly remain a formidable challenge. Here we present a novel mesoscale model for soft Janus particles, which successfully reflects their physical nature by directly mapping onto experimentally measurable particle properties. By properly tuning Janus balance and the strength of attraction between attractive patches, soft Janus particles can reversibly self-assemble into a number of fascinating hierarchical superstructures in dilute solutions, such as micelles, wormlike strings, single helices, double helices, bilayers, tetragonal bilayers, and complex supermicelles. Our work demonstrates that soft Janus particles with deformable and non-centrosymmetric characteristics hide many surprises in the design and fabrication of hierarchically self-assembled superstructures.

By using computer simulations, we propose a simple route to fabricate 7–17 nm particles with controllable patch symmetry viaself-assembly of a polymer chain in one step. A single chain of polystyrene-polymethylmethacrylate (PS-PMMA) multiblock copolymer, which is intended to be a generic representative for common hydrophobic multiblock copolymers, is used to fabricate the patchy particles in a solvent that is poor for both components. Various kinds of patchy particles, such as one-patch (with C∞v symmetry), two-patch (with D∞h symmetry), three-patch (with D3hsymmetry), four-patch (with Td symmetry), and cross-ribbon patchy particles, have been obtained. Our work demonstrates that a rational bottom-up design of patchy nanoparticles with controllable symmetry is possible by manipulating the block copolymer chain length and solvent quality.

Polymer gel exists ubiquitously in our daily life, as in food, cosmetics, drugs, and so on. From the structural point of view, the 3D network can be found in a structural gel. In most experimental work, the gel is identified by the sharp increase in modules; that is, the gel should have similar properties as those of a solid, which is named as mechanical gel. However, not all structural gels have strong mechanical responses. Therefore, studying the relationship between structural gel and mechanical gel is very important. In this work, we investigate the structure and mechanical properties of symmetric ABA copolymers with solvophobic end blocks during the sol–gel transition. Three typical systems with weak, middle, and strong solvophobicities are simulated. It is found that the gelation concentration, gel structure, and mechanical response of structural gel are strongly affected by the solvophobicity of ABA block copolymer. We also find that only the gel formed in strong solvophobic systems has a strong mechanical response. Furthermore, the influence of solvophobicity of A-block on the static and dynamic properties of ABA block copolymers in solutions is also studied to give a molecular understanding of physical gelation.

Transport of star polymers under pressure-driven flow in a pipe with pipe radius being at least twice the size of polymers has been examined with standard dissipative particle dynamics (DPD) simulations. Equilibrium dynamics of star polymers in bulk solution were found to obey the Zimm model very well, indicating that DPD simulation correctly incorporates the hydrodynamic interaction in the stars. Under pressure-driven flow, star polymers with more arms were found to migrate toward the center of pipe more, leading to a net faster velocity and hence a shorter retention time in the pipe. The stretching of star polymers along the flow was found to follow similar scaling behavior as the linear polymer chains, except that the Weissenberg number Wi for the stars should be reduced by arm number f. After rescaling of the Weissenberg number, the stretch ratio Sx, defined as the ratio of square of radius gyration of the chains along the flow, Rgx2, over its corresponding value in dilute bulk solution, was found to scale with Wi linearly when Wi ≫ 1. The compression of the chains in the dimension perpendicular to the flow Sy were found to scale with Wi−0.5 when Wi ≫ 1.0.