Linli He

Helical conformations of semiflexible polymers confined between two concentric cylinders.

An off-lattice Monte Carlo method was used to study the conformational properties of semiflexible chains confined between two concentric cylinders. The conformations of confined semiflexible chains depend on the bending energy as well as the size of confinement, and the semiflexible chains with particular rigidities confined in the appropriate spaces can form helical structures under entropically driven. The inner cylinder plays a key role in the formation of helical conformations, whereas the outer cylinder affects the size of confinement. Furthermore, the helical structures keep fluctuating like a harmonic oscillation, and the clockwise or counterclockwise helical conformations will appear with the same possibility in the processes of relaxation-helix transitions. This study can help us understand the conformational behaviors of biological macromolecules in confined space.

Ordered structures of diblock nanorods induced by diblock copolymers

The self-assembly of diblock copolymer (DBCP)/diblock nanorod (DBNR) mixtures are studied by using a dissipative particle dynamics simulation method. The microstructures of DBCP/DBNR blends depend on the type of DBCPs as well as the number of DBNRs. For the asymmetric DBCPs of A3B7, the morphological transition of DBCP/DBNR blends from cylinder phase to lamellar phase is observed for the DBNRs with suitable length and component. Meanwhile, for the symmetric DBCPs of A5B5, the lamellar morphologies of DBCP/DBNR blends can always maintain during the process of adding DBNRs to the blends except for the case of component length mismatch between the DBCPs and the DBNRs. On the other hand, DBCPs can also affect the orientation and the spatial distributions of DBNRs deeply, and the ordered structures of DBNRs are formed for the DBCP/DBNR blends with a large number of DBNRs. Comparisons with homopolymer/DBNR blends are made, and only the aggregation structures are observed in homopolymer/DBNR blends. This investigation can provide valuable assistance in exploring and designing complicated polymer/nanoparticle composites with the desired properties.

Self-assembly of nanorods on soft elastic shells

The self-assembly behavior of nanorods (NRs) on soft elastic shells is investigated using the molecular dynamics (MD) simulation method. The self-assembly structures of the adsorbed nanorods depend on the length of the nanorods as well as the bending energy of the soft elastic shells. For short nanorods, the aggregates consist of regular pentagons around the gibbosity at low bending energies, and the ordered structures are gradually broken when the bending energy increases. In the meantime, the adsorption ability of the nanorods on the elastic shells decreases when the binding energy increases. For long nanorods, the binding energy can induce the nanorods to aggregate in clusters on shells with low or moderate bending energy, and each cluster is formed by several parallel long nanorods. However, the self-assembly structures of long nanorods disappear for shells with high bending energy because the adsorption becomes isotropic for nanorods on a rigid shell. Meanwhile, the adsorption of nanorods on the shell can also affect the shape of the soft elastic shell, especially for long nanorods. This investigation can help us understand the complexity of the self-assembly of nanorods on an elastic shell.

Adsorption Behavior of Polymer Chain with Different Topology Structure at the Polymer-Nanoparticle Interface

The effect of the polymer chain topology structure on the adsorption behavior in the polymer-nanoparticle (NP) interface is investigated by employing coarse-grained molecular dynamics simulations in various polymer-NP interaction and chain stiffness. At a weak polymer-NP interaction, ring chain with a closed topology structure has a slight priority to occupy the interfacial region than linear chain. At a strong polymer-NP interaction, the “middle” adsorption mechanism dominates the polymer local packing in the interface. As the increase of chain stiffness, an interesting transition from ring to linear chain preferential adsorption behavior occurs. The semiflexible linear chain squeezes ring chain out of the interfacial region by forming a helical structure and wrapping tightly the surface of NP. In particular, this selective adsorption behavior becomes more dramatic for the case of rigid-like chain, in which 3D tangent conformation of linear chain is absolutely prior to the 2D plane orbital structure of ring chain. The local packing and competitive adsorption behavior of bidisperse matrix in polymer-NP interface can be explained based on the adsorption mechanism of monodisperse (pure ring or linear) case. These investigations may provide some insights into polymer-NP interfacial adsorption behavior and guide the design of high-performance nanocomposites.