Recently, the use of hybrid double network (DN) hydrogels has become prominent due to their enhanced mechanical properties, which has opened the door for new applications of these soft materials. Only a few of these gels have demonstrated both injectable and moldable capabilities. In this work, we report the mechanical properties, gauge factor (GF) values and demonstrate both the injectability and moldability of a gelatin/polyacrylamide DN hydrogel. We optimized several parameters, such as, gelatin to polyacrylamide ratio, reactant concentrations and metal ion concentration, to produce a gelatin/polyacrylamide hydrogel with superior mechanical properties. The highest water content gel was capable of withstanding strains of 5000% before failure. These gels were facilely injected into molds where they effectively changed shape and maintained similar properties prior to remolding. When 20 mM calcium was doped into a similar gel, a tensile strength of 1.71 MPa was achieved. Aside from improving the mechanical properties of the gels, both Ca2+ and Mg2+ also improved their conductivity, so they were tested for use as strain sensors. The sensitivity of the hydrogel strain sensors were measured using the GF. For the 20 mM Ca2+ hydrogel, these GF values ranged from 1.63 to 6.85 for strains of 100% to 2100% respectively. Additionally, the sensors showed good stability over continuous cyclic stretching, demonstrating their long term reliability for strain sensing.

The chemical treatment of wood has been shown to increase its mechanical strength by forming composites with a variety of polymers. Polyethylene glycol diacrylate (PEGDA) has commonly been used as a polymer reinforcement to increase the strength and resistance of spruce wood for various applications, such as protection from weathering. In this study, PEGDA was impregnated into wood samples and polymerized by dielectric barrier discharge (DBD) plasma to form wood–polymer composites (WPCs). The kinetic rate order of PEGDA was explored using FT-IR quantitative analysis and the DBD plasma-initiated polymerization was determined to be second order. The strength of the wood samples was then determined by a three-point flexural test. The PEGDA-treated spruce wood samples showed improved flexural strength versus the untreated wood samples. The WPCs were also made using a UV treatment method and were then compared to the DBD plasma-treated samples. The results showed that the DBD plasma-treated samples yielded superior flexural strength relative to the UV-treated samples. We accredited this difference in strength to the plasma process and its ability to penetrate into the various layers of the wood and initiate polymerization, as opposed to UV light that can only penetrate superficially, initiating polymerization in only the first few layers of the wood surface.

This research investigated a non-thermal, dielectric-barrier discharge (DBD) plasma-based approach to prepare poly(acrylic acid) (PAA) from acrylic acid in its liquid state at atmospheric temperature and pressure. Neither additives nor solvents were needed, and the polymerization was accomplished both as a film and inside a sheet of mesoporous paper. All prepared samples were characterized and the DBD plasma-initiated kinetics were analyzed for the polymerization of acrylic acid. Using FTIR semi-quantitative analysis, the degree of polymerization was monitored, and the reaction followed an overall second-order kinetic model with respect to the DBD-initiated polymerization. Additionally, the application of a PAA-modified paper as a water retention cloth or ‘wet wipe’ was investigated. The results showed that the PAA-modified paper substrates using DBD plasma increased water retention as a function of plasma treatment time.