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Natural compounds cholic acid and β-cyclodextrin are attached separately as pendant groups in a copolymer with N,N′-dimethylacrylamides. The formation of supramolecular hydrogels is induced by inclusion complex formation between cholic acid and β-cyclodextrin moieties as evidenced by rheological analysis and 1 H NMR spectroscopy. Storage modulus of the hydrogel shows a maximum value when the molar ratio of cholic acid to β-cyclodextrin units is adjusted to 1:1. The concentration of the hydrogel can be as low as 5.5 wt %. Both shear-thickening and shear-thinning have been observed when the shear rate gradually increases from 0.01 to 100 s −1 . The inclusion complexation renders the gel−sol process reversible under heating and cooling cycles. The self-healing of such hydrogels is observed and confirmed by step-strain rheological measurements. The dynamically reversible host−guest complexation provides reasonably good mechanical properties of the cross-linked polymer network. The natural origin of the constituents may make the hydrogels suitable candidates for biomedical applications pending further tests.

Two-way reversible shape memory polymers (2W-SMPs) are highly desirable for many applications. We report for the first time the use of random copolymers with cocrystallizable monomeric units for the preparation of such polymer networks. Homopolymers and random copolymers of ε-caprolactone and ω-pentadecalactone were designed and made by ring-opening polymerization with Candida antarctica lipase B as catalyst. The melting temperatures of these prepolymers may be adjusted by the use of various molar ratios of the comonomers. Upon thiol–ene cross-linking, the polymer network exhibited two-way reversible shape memory effects under both stress-free and stress conditions. The actuation temperature (T A) of the 2W-SMP under stress-free condition can be tuned in a broad range using a selected mixture of prepolymers followed by photo-cross-linking with a multifunctional cross-linker. Increasing the initial stretching stress amplitude led to an increased absolute strain change under both stress-free and stress condition; it led to a reduced relative strain change under stress-free condition, but almost no change under stress condition. The evolution of the microstructure of 2W-SMPs under stress-free condition cycle was studied by the use of X-ray diffraction (2D-WAXD and SAXS). This is the first report on the tuning of T A of 2W-SMPs under stress-free condition by the use of one or two prepolymers to form a chemically cross-linked network. We have also eliminated the use of toxic metal catalysts in the synthesis of polymeric biomaterials. The materials are shown to be capable of performing reversible bending–unbending and coiling–uncoiling motions.

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With the rapid application of light-curing 3D printing technology, the demand for high-performance polymer resins is increasing. Existing light-curable resins often have drawbacks limiting their clinical applications. This study aims to develop a new type of polymethyl methacrylate (PMMA) composite resins with enhanced mechanical properties, high antibacterial activities and excellent biocompatibilities. A series of reinforced composite resins were prepared by mechanically mixing PMMA with modified cellulose nanocrystals (CNCs), which were coated with polydopamine and decorated by silver nanoparticles (AgNPs) via Tollen reaction. The morphology of CNCs-Ag was observed by transmission electron microscopy and the formation of AgNPs on CNCs was confirmed by X-Ray photoelectron spectroscopy analyses. Functional groups in PMMA-CNCs-Ag composites were verified by Fourier Transform infrared spectroscopy (FTIR) spectroscopy. The mechanical assessment and scanning electron microscopy analysis suggested that the evenly distributed CNCs-AgNPs composite effectively improve mechanical properties of PMMA resin. Cytotoxicity assay and antibacterial activity tests indicated excellent biocompatibility and high antibacterial activities. Furthermore, PMMA with CNCs-AgNPs of 0.1 wt.% (PMMA-CNCs-AgNPs-0.1) possessed the most desirable mechanical properties owing to the homogeneous distribution of AgNPs throughout the resin matrix. This specific composite resin can be used as a functional dental restoration material with potential of other medical applications.