Rong Ran

Self-healable, tough and highly stretchable hydrophobic association/ionic dual physically cross-linked hydrogels

Hydrophobic association (HA) hydrogels have recently attracted much attention since they exhibit high self-healing ability, remolding capability and shape-memory behavior simultaneously, but their low mechanical strength prevents them from use in many stress-bearing applications. In this work, we describe a novel method for the production of tough and highly stretchable hydrogels with self-healing behavior, tensile strength of 150–300 kPa and stretch at break of 2400–2800%. Dual physical cross-linking (DPHF) hydrogels were prepared via micellar copolymerization of acrylic acid (AA) and stearyl methacrylate (C18) in an aqueous ferric chloride solution with two different types of surfactant, cetyltrimethylammonium bromide (CTAB) and sodium dodecyl benzene sulfonate (SDBS). The mechanical, rheological, self-healing and swelling properties of the DPHF hydrogels were investigated and also evaluated as a function of the type of surfactant and the content of ferric ions. The introduction of a moderate content of ferric chloride endowed the hydrogels with excellent strength and self-healing properties simultaneously. Moreover, the structure of the DPHF hydrogels was investigated by IR and SEM analysis. The results were consistent with the results of the mechanical, self-healing and swelling properties tests.

A mechanically robust double-network hydrogel with high thermal responses via doping hydroxylated boron nitride nanosheets

Double-network (DN) hydrogel which possesses many superior performances such as excellent toughness, viscoelasticity and self-healing ability has become promising biomaterials. However, lack of thermal conductivity and moderate adhesiveness has greatly limited their application as load-bearing cartilage substitutes. Boron nitride itself has good rigidity and thermal conductivity but poor water solubility. Hydroxylated boron nitride nanosheets (OH-BNNSs) which have been previously reported have good water solubility (~u20090.6xa0mg/mL) and to obtain a homogeneous and stable dispersion. In this work, we introduced OH-BNNS into DN hydrogel to obtain high thermal conductivity and toughness hydrogel. The DN hydrogel is a class of physically double-network hydrogel with hydrophobic association polyacrylamide (PAM) and partly crystalline polyvinyl alcohol (PVA). Impressively, the obtained PVA/PAM/BNNS composite hydrogel possesses super-flexibility, high toughness, good thermal conductivity, appropriate tissue adhesiveness and stimuli-free self-healing ability. Therefore, the composite hydrogel overcomes the poor mechanical strength and locally overheating issues as cartilage substitutes and may also become alternatives for antipyretic pastes.

A novel self-assembled hybrid organogel of polypeptide-based block copolymers with inclusion of polypeptide-functionalized graphene

Self-assembled hybrid organogels of polypeptides containing block copolymers with the inclusion of polypeptide-functionalized graphene were designed and elaborately prepared, and showed interesting microstructures as well as enhanced mechanical performances. Firstly, a series of peptide-based triblock copolymers (triBCPs), poly(γ-benzyl-L-glutamate)-b-poly-(dimethylsiloxane)-b-poly(γ-benzyl-L-glutamate) (PBLG-b-PDMS-b-PBLG, BDB), with different lengths of PBLG helices, were synthesized and characterized. As the length of the PBLG helices increased, the critical gelation concentration of the BDB triBCPs decreased while the gel–sol transition temperature increased. Moreover, the PBLG covalently modified graphene oxide (GO) sheets were successfully incorporated into the BDB organogels in toluene and hybrid organogels were prepared. In the presence of GO sheets, the minimum gelation concentration of the hybrid organogel was slightly lowered, and the hybrid organogels preserved thermoreversibility. In the hybrid gels, the triBCPs still self-assembled into nanoribbon structures and the functionalized GO sheets were well dispersed in the gel medium, which was obviously observed by transmission electron microscopy. In addition, the inclusion of the functionalized graphene greatly enhanced the mechanical performance of the hybrid gels, which was demonstrated by the significant increase of the moduli and the fracture stress of the hybrid gels compared with the corresponding native gels in the rheology experiments.