Self-assembly behaviors of polymer-tethered nanorods in the selective solvent are systematically investigated via a dissipative particle dynamics (DPD) simulation method. Three types of polymer-tethered nanorods are considered: one end tethered, both ends tethered, and middle tethered. The solvent-induced diverse morphologies and morphological transitions depend on the topology, rod/tether length ratio, solvent selectivity, and mixed solvent content. In the pure rod-selective solvent (solvent I) or the pure tether-selective solvent (solvent II), the ordered micellar structures include: cylinders, hexagonal cylinders, bilayer lamellae, lamellae/cylinder mixed phases, inverted hollow cylinders, and nematic bundles. These micelles are formed by the competition among the stretching of tethers, liquid crystalline of rods, interfacial energy, and solvent selectivity. In the I/II mixed solvent, with varying mixed solvent content in sequence (i.e., changing the solvent quality for the blocks), the reversible morphological transitions and fantastic intermediate phases (e.g., liquid crystalline phase) are observed, which correspond directly to the case of that induced by varying the rod/tether length ratio in the pure solvent. It is concluded that improving the selective solvent content is equivalent to increasing the soluble block ratio. The present study reveals that the morphology and morphological transition of polymer-tethered nanorods could be significantly manipulated through topology, block length, and solvent, especially the selectivity.

COVID-19 presents unprecedented challenges to the global public health response. Preventive behaviors and keeping social distance are regarded as compelling ways to prevent COVID-19. This study focused on the sociological and psychological factors associated with proper and excessive preventive behaviors of the COVID-19 outbreak in China. For the sample, we collected the data of 4788 participants who were surveyed between 4 April and 15 April 2020 from eight provinces in China. This study designed a self-filled questionnaire that included demographic information, six components of the Health Belief Model, and target preventive behaviors. Descriptive analysis, Chi-square test, logistic regression analysis, Mantel–Haenszel hierarchical analysis, and propensity score matching were employed in this study. The results showed that 54.7% of the participants had adequate basic prevention, 63.6% of the participants had adequate advanced prevention, and 5.8% of the participants practiced excessive prevention. The elder participants were less likely to engage in proper preventive behaviors. Perceived susceptibility, perceived benefits, perceived barriers, cues to action, and knowledge levels were associated with preventive behaviors. Excessive preventive behaviors in high-risk groups with suspected symptoms were associated with their extreme psychological condition, while the support from the community and family plays an important role in avoiding these behaviors.

The effects of applied magnetic field on the system composed of polymer brushes and magnetic particles are studied by means of Monte Carlo simulation. The direction of the applied magnetic field is chosen to be perpendicular to the substrate plane. Polymer brushes and magnetic particles are attracted to each other. The average heights of polymer brushes depend not only on the strength of applied magnetic field (H) but also on the brush grafting density (r) and the chain length (N). The applied magnetic field influences the arrangement of magnetic particles, and in turn, the arrangement of magnetic particles affects the spatial distribution of polymer brush monomers. When the strength of the magnetic field is increased, the average height of polymer brushes will be increased accordingly. The reason is that the orientations of the magnetic moments of particles must be along the mag-netic field direction, and this leads polymer brushes to rearrange along the magnetic field direction. At the same time, the chain length and the grafting density of polymer brushes have also effects on the properties of the magnetic particles, such as the magnetic particles distribution, magnetic susceptibility, and pair correlation functions. Comparisons with the experimental ones are also made, and this investigation can provide some insights into statistical properties of magnetic particle-loaded brushes induced by external magnetic field.