发表论文

The capability of polyelectrolyte brushes to spontaneously clean oil fouling via water is determined by factors including water wettability and the self-assembled structures of hydrated polyelectrolytes. Although the charged groups of polyelectrolytes provide the original source of water wettability, the self-assembled structures play a significant role in the self-cleaning performances. Here, we employ coarse-grained molecular dynamics simulations to study the general self-cleaning characteristics of two types of surface-grafted polyelectrolyte brushes (i.e., zwitterionic and anionic polyelectrolytes). It has been found that the high grafting density is favorable to fouling reduction for both polyzwitterions and polyanions. To be specific, the hydrated polyzwitterions form an intermolecular cross-linked network via zwitterionic complexes, resulting in better self-cleaning capabilities than the polyanions at lower grafting densities. However, polyanions form bundles with each consisting of several chains via hydrophobic interactions and electrostatic repulsions presenting better self-cleaning performances than the polyzwitterions at higher grafting densities.

We present a systematic investigation on the effect of adding nanoparticles on the dynamics of polymer chains by using coarse-grained molecular dynamics simulation. The dynamics is characterized by three aspects:molecular motion, relaxation at different length scales, and dynamical heterogeneity. It is found that the motion of polymer chains slows down and the deviation from Gaussian distribution becomes more pronounced with increasing nanoparticle volume fractions. For polymer nanocomposites with R ≤ Rg, the relaxation at the wave vector q = 7.0 displays multistep decay, consistent with the previous reports in strongly interacting polymer nanocomposites. Moreover, a qualitatively universal law is established that dynamic heterogeneity at whole chain’s scale follows a nonmonotonic increase with increasing nanoparticle loadings, where the volume fraction of the maximum dynamic heterogeneity corresponds to the particle loading when the average distance between nanoparticles is equal to the Kuhn length of polymer chains. We show that the decoupling between whole chain’s dynamics and segment dynamics is responsible for the nonmonotonic behavior of dynamic heterogeneity of whole chains.

We perform dynamics simulations to investigate the translational and rotational glassy dynamics in a glass-forming liquid of monodisperse soft Janus particles. We find that, with decreasing temperature, the mean-square angular displacement shows no clear plateau in the caging region, in contrast with the apparent caging behavior of translational motion. By defining a reorientational mean-square angular displacement, the caging behavior of rotational motion can be recognized. On approaching the glass transition (decreasing temperature), the coupling between translational and rotational relaxation increases, while the coupling between translational and rotational diffusion decreases, whereas the coupling between translational and reorientational diffusion increases. The strong decoupling between translational and rotational diffusion is due to the suppressed translational mobility but promoted rotational mobility of soft Janus particles. We think that the low-T SE and SED decoupling is mainly attributed to hopping motion of soft Janus particles, whereas the high-T SE and SED decoupling is mainly attributed to collective cage motion of soft Janus particles. Our results demonstrate that interaction anisotropy has a critical effect on the translational and rotational dynamics of soft Janus particles.

采用软补丁粒子模型及相应的介观动力学模拟方法, 研究了软三嵌段两面神胶体粒子在稀溶液条件 下的自组装行为. 通过合理调节补丁大小和补丁之间的吸引强度, 软三嵌段两面神胶体粒子能够自组装形成 非常丰富的聚集结构, 包括线状结构、 六方柱状结构、 体心四方束状结构以及三维网络状结构. 此外, 分析 了与纤维结构类似的体心四方束状结构形成的动力学机理. 模拟结果为实验上设计并制备新颖的超胶体纳 米结构提供一定的理论支持.

Self-assembly in nature is fundamentally dynamic, existing in out-of-equilibrium state in which the systems have the ability to autonomously respond to environmental changes. However, artificial systems exist in a global minimum state, which are incapable of conducting such complex functions. Here we report that input of thermal energy can trigger fixed, artificial toroids to spontaneously nucleate helical growth. The helical polymerization undergoes reversible and repeatable cycles with subsequent energy input. When the toroids are located inside lipid vesicles, the polymerization-depolymerization cycle is accompanied by reversible elongation of spherical vesicles. Such liberation from a global minimum state will pave the way to create emergent structures with functions as complex as those of living systems.

利用广义指数模型描述软胶体粒子, 结合分子动力学模拟研究软胶体粒子形成束晶的动力学过程. 通 过等温压缩和等密度降温 2 个不同的过程, 研究了束晶形成过程中结构变化特征和动力学路径对结构的影响规律. 研究发现, 与蒙特卡洛模拟结果相比, 分子动力学模拟得到的结构随着密度的变化有明显的迟滞现象, 这是由于考虑了真实的动力学因素引起的差异. 此外, 在相同温度和压力下通过不同的动力学路径得到 的相结构不完全相同, 这是由于动力学形成过程会对相结构产生很大的影响.

An ionic porous aromatic framework, iPAF-1, was successfully synthesized from a designed monomer with imidazolium functional groups. The iPAF-1 exhibits the highest dibenzothiophene uptake among all reported adsorptive desulphurization adsorbents. The so-called precursor designed synthetic route provides the stoichiometric and homogeneous introduction of desired functional groups into the framework. Molecular dynamics simulation was performed to understand the structure and the desulphurization process within the amorphous iPAF-1. The insight into the key role of the moderate bonding interaction between the adsorbate and the functional groups of iPAF-1 for improved uptake is highlighted in this work.

The separation of acetylene from ethylene is a crucial process in the petrochemical industry, as even small acetylene impurities can lead to premature termination of ethylene polymerization. Herein, we present the synthesis of a robust, crystalline naphthalene diimide porous aromatic framework via imidization of linear naphthalene-1,4,5,8-tetracarboxylic dianhydride and triangular tris(4-aminophenyl)amine. The resulting material, PAF-110, exhibits impressive thermal and long-term structural stability, as indicated by thermogravimetric analysis and powder X-ray diffraction characterization. Gas adsorption characterization reveals that PAF-110 has a capacity for acetylene that is more than twice its ethylene capacity at 273 K and 1 bar, and it exhibits a moderate acetylene selectivity of 3.9 at 298 K and 1 bar. Complementary computational investigation of each guest binding in PAF-110 suggests that this affinity and selectivity for acetylene arises from its stronger electrostatic interaction with the carbonyl oxygen atoms of the framework. To the best of our knowledge, PAF-110 is the first crystalline porous organic material to exhibit selective adsorption of acetylene over ethylene, and its properties may provide insight into the further optimized design of porous organic materials for this key gas separation.

The construction of excellent porous organic frameworks (POFs) with high surface areas and stability is always a tremendous challenge in synthetic chemistry. The geometric configuration and reactive group of building unit are crucial factors to influence the structure and porosity of the resulting product. Herein, the design, synthesis, and characterization of two porous aromatic framework (PAF) materials, named PAF-100 and PAF-101, are reported via a strategy of building unit engineering. PAF-100 and PAF-101 present high Brunauer–Emmett–Teller surface areas exceeding 5000 m2 g−1 and uniform pore size distributions. Furthermore, PAF-100 and PAF-101 show high methane uptake with value of 742 and 622 cm3 g−1, respectively, at 298 K and 70 bar. The successful synthesis of PAFs with exceptional porosity from engineered building unit is powerful for constructing highly porous POFs.

All-polymer solar cells (APSCs), composed of semiconducting donor and acceptor polymers, have attracted considerable attention due to their unique advantages compared to polymer-fullerene-based devices in terms of enhanced light absorption and morphological stability. To improve the performance of APSCs, the morphology of the active layer must be optimized. By employing a random copolymerization strategy to control the regularity of the backbone of the donor polymers (PTAZ-TPDx) and acceptor polymers (PNDI-Tx) the morphology can be systematically optimized by tuning the polymer packing and crystallinity. To minimize effects of molecular weight, both donor and acceptor polymers have number-average molecular weights in narrow ranges. Experimental and coarse-grained modeling results disclose that systematic backbone engineering greatly affects the polymer crystallinity and ultimately the phase separation and morphology of the all-polymer blends. Decreasing the backbone regularity of either the donor or the acceptor polymer reduces the local crystallinity of the individual phase in blend films, affording reduced short-circuit current densities and fill factors. This two-dimensional crystallinity optimization strategy locates a PCE maximum at highest crystallinity for both donor and acceptor polymers. Overall, this study demonstrates that proper control of both donor and acceptor polymer crystallinity simultaneously is essential to optimize APSC performance.