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Understanding the interplay among the mechanical behavior, ionic conductivity and chain dynamics of ionogels is essential for designing flexible conductors that exhibit both high conductivity and excellent mechanical properties. In this study, ionogels were synthesized via the radical polymerization of N , N '-dimethylacrylamide (DMAA) and methacrylic acid (MAAc) monomers in the presence of ionic liquid 1-ethyl-3-methylimidazolium trifluoromethane sulfonate ([EMIM][OTf]). By varying the mass content of ionic liquid within ionogels, we investigated the mechanical behavior and ionic conductivity at the macroscopic scale using tensile, rheological testing and electrochemical impedance spectroscopy, as well as the dynamic behavior of chain segments and ions within the network at the microscopic scale using broadband dielectric relaxation spectroscopy (BDS) over a broad temperature range. Our findings revealed that variations in ionic liquid concentration significantly affect mechanical performance, ionic conductivity, complex conductivity spectra, and complex permittivity spectra. These ionogels exhibited remarkable stretchability, adhesion, and strain-sensing capabilities. Analysis of BDS indicated that the temperature dependence of the hopping frequency ( ω H ), the conductivity of free ions ( σ dc ), and the relaxation time ( τ s ) of chain segments conforms to the Vogel-Tammann-Fulcher (VTF) equation for ionogels with varying ionic liquid content. By correlating τ s measured through rheological tests and BDS, we observed a transition from Arrhenius to VTF behavior, which shifts towards lower temperatures with increasing ionic liquid content. This study highlighted a strong coupling between σ dc and ω H , as well as between 1/ τ s and ω H , at low ionic concentrations, facilitating high mechanical performance of the ionogels due to viscoelastic energy dissipation. However, as the ionic concentration increased, a slight decoupling of σ dc and ω H was noted, leading to a substantial reduction in the mechanical properties of the ionogels. Ultimately, these ionogels demonstrate potential as polymer electrolytes for applications in flexible wearable devices.

Dynamic surfaces which can change their topography with external stimuli have wide application prospects. Liquid crystal network (LCN) is an ideal material for making dynamic surfaces, but traditional methods for LCN dynamic surface manufacturing are difficult to scale up, which limits its applications. This research proposes a new method to fabricate a responsive surface using ink-jet printing technology. Using a liquid crystal monomer mixture as the ink, we printed arrays of droplets onto a glass substrate with a homeotropic alignment layer and polymerized the droplets into deformable LCN hemispheres. An azobenzene diacrylate was copolymerized into the hemispheres to make them photo-responsive to UV light. Because the ink-jet printing method can potentially be used to print countless hemispheres on a large area substrate, large area dynamic surfaces consisting of a multitude of separate dynamic structures can be manufactured. Since the deformation of the entire surface is a periodic repetition of the deformation of a single hemisphere, we characterized the deformation of individual hemispheres, and found that the optical image of hemispheres between crossed polarizers shows a "maltese cross" texture, and 3D surface profiling shows the top surface depresses into a valley after UV-irradiation. This is caused by an order parameter decrease of the homeotropically aligned LC molecules, which leads to a contraction in the alignment direction. The deformation amplitude can be modulated by UV intensity and temperature. This kind of dynamic surface fabricated by ink-jet printing technology can easily be scaled up and is promising for applications such as adjustable micro-lenses or surface wettability.

The scaffold is one of the most important components in tissue engineering. There are a lot of natural or synthetic materials applied for the fabrication of scaffolds. Among them, cellulose nanofibril (CNF) is an important natural polymer with characteristics of superior biocompatibility, notable nanostructure effect and excellent hydrophilia, which make it qualified for serving as a raw material of scaffolds. In this paper, polyethylene glycol diacrylate (PEGDA) was mixed with CNF at different content ratios, which were 0%, 0.35%, 0.7%, 1.05% and 1.4% (m/v). Furthermore, the visible light photoinitiator (eosin Y + TEA + NVP) was first added to this mixture solution to form a new kind of bio-resin. A two-step method including stereolithography and freeze-drying is put forward to fabricate a new aerogel-wet hydrogel scaffold. Scaffolds were fabricated by using a self-built stereolithography platform and the mechanical properties, printability and biocompatibility of the hydrogel scaffolds were investigated thoroughly. The original hydrogel scaffold was fabricated through stereolithography, where CNFs were applied to regulate the mechanical properties of the hydrogel and the printability of the bio-resin. After the freeze-drying process, the original hydrogel was transformed into the aerogel-wet hydrogel whose compressive modulus is reduced by 20%. Furthermore, the surface structure of the hydrogel scaffold is modified to provide a better environment for adhesion and growth of BMSc.

The pore structure of TEMPO-mediated oxidized CNF hydrogels, chemically cross-linked with water-soluble diamines, is studied. A solute exclusion method and pulsed-field-gradient NMR are used to estimate the mesh size distribution in the gel network in its hydrated state. Dextran fractions with the nominal molecular weights in the range of 10-2000 kDa are used as probes. The results show a nonuniform network structure, consisting of a group of large openings that contain ∼50% of water, and regions with a more compact structure and smaller mesh units that restrict the diffusivity of the dextran molecules. A biexponential model is proposed for the NMR echo amplitude decay due to the probe diffusion into the gel network. A typical single exponential model does not fit the experimental data when the probe molecular size is comparable to the network mesh size. The results obtained with NMR, using the proposed biexponential model, are in very good agreement with those determined with solute exclusion. Precise mesh size estimation with solute exclusion using pore models is subject to restrictions, and vary with the assumed pore geometry. The average mesh size obtained using a spherical pore model, ∼35 nm, in the compact regions of the hydrogel, is in good agreement with the theoretical value in a network of rodlike particles. Neglecting the wall effects leads to underestimation of the mesh size with both techniques.