Xin Qian

Double-network hydrogels based on two natural polysaccharide polymers, locust bean gum and gellan gum, have been fabricated and exhibited excellent self-healing, thermo-processability, and pH-driven shape memory properties.

Coarse-grained molecular dynamics simulations were carried out to identify the conditions under which the nanorods (NRs) side-grafted with polymer chains can assemble in end-to-end configurations in a homopolymer matrix, a structure of significant importance for optimal property characteristics. Our results demonstrate that by adjusting the grafting density and the grafted chain length, three different NR morphologies can be obtained, viz., side-by-side aggregation, end-to-end alignment and homogeneous dispersion. To understand the underlying mechanism, the chain characteristics around the NRs were systematically investigated. We find that the transition of NR morphologies from side-by-side aggregation to others is correlated to the mushroom-to-brush transition of the grafted chain configurations. At high grafting densities corresponding to the brush regime, the entropic steric repulsions between the polymer brushes prevent the NRs from approaching in side-by-side configurations. Instead, end-to-end assembly and homogeneous dispersion are observed. Within such regimes, we observe that the splaying of the grafted polymer chains at the edges of the NRs plays a critical role in determining the occurrence of end-to-end assembly. When the extent of splaying cannot overcome the van der Waals and depletion attractions between the NR ends, which occurs at relatively short graft lengths, the end-to-end assembly is preferred. We find that this manner of self-assembly will be further promoted by increasing the NR loading but is retarded by increasing the NR aspect ratio. In general, our study identifies conditions to enable the end-to-end assembly of NRs in a homopolymer matrix, enabling significant practical applications.

In this study, we prepared short‐carbon‐fiber (CF)‐reinforced poly(lactic acid) (PLA)–thermoplastic polyurethane (TPU) blends by melt blending. The effects of the initial fiber length and content on the morphologies and thermal, rheological, and mechanical properties of the composites were systematically investigated. We found that the mechanical properties of the composites were almost unaffected by the fiber initial length. However, with increasing fiber content, the stiffness and toughness values of the blends were both enhanced because of the formation of a TPU‐mediated CF network. With the incorporation of 20 wt % CFs into the PLA–TPU blends, the tensile strength was increased by 70.7%, the flexural modulus was increased by 184%, and the impact strength was increased by 50.4%. Compared with that of the neat PLA, the impact strength of the CF‐reinforced composites increased up to 1.92 times. For the performance in three‐dimensional printing, excellent mechanical properties and a good‐quality appearance were simultaneously obtained when we printed the composites with a thin layer thickness. Our results provide insight into the relationship among the CFs, phase structure, and performance, as we achieved a good stiffness–toughness balance in the PLA–TPU–CF ternary composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46483.

This work reports the steady shear induced aligning behaviour of nanoparticle strings in a functionalized polymer matrix.