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Despite tremendous attention to hydrogel-based wearable strain sensors, it is still challenging to develop an all-in-one hydrogel possessing desired properties of ultra-stretchability, extraordinary conductivity and high strain sensing. Herein, instead of conventional chemical cross-linking, polyacrylamide (PAAm) hydrogel is cross-linked with hydrophobic association (HA), and is further reinforced with cellulose nanocrystals (CNCs), yielding a robust HAPAAm/CNC hydrogel. Subsequently, the HAPAAm/CNC is sequentially immersed into acidic solutions with various concentrations of aniline and initiator (0.5 M is optimal), leading to polymerization of aniline monomers inside the hydrogel. The optimal hydrogel (HAPAAm/CNC/polyaniline (PAni)-0.5), has great stretchability (≈2400%) and skin-like Young's modulus (30 kPa). It also shows outstanding electrical conductivity (21.7 S m−1), thanks to conductive pathways provided by PAni nanofibers. Such a combination of great mechanical and electrical properties has never been reported for PAni-based hydrogels. The resultant hydrogel can sense strains as low as 1%, while also measuring strains up to 1000%. Besides having linearity, the hydrogel sensor has a high gauge factor (GF = 3.7) within a range of 0–200%, exceeding that of many reported PAni-based hydrogel sensors. The hydrogel sensor can detect human motions from large strains to minor ones (e.g., breathing). Therefore, HAPAAm/CNC/PAni-0.5 shows great promise for soft electronics. [ABSTRACT FROM AUTHOR]

The influence of fumed nano-SiO2 on the performance of a typical tire tread compound, fabricated by mechanical mixing process, was investigated in the present research. The tire tread compound contained styrene-butadiene rubber (SBR)/ cis -butadiene rubber (BR) blend reinforced with a well-developed commercial highly dispersive silica filler at 70 phr loading. Nano-SiO2 with higher specific surface area, e.g., ∼240 m2/g, was substituted partially with silica particle at three different concentrations of 5, 10, 15 phr. Improvement in various aspects of the control sample including crosslink density calculated based on the swelling test and tube theory, bound rubber content, and physico-mechanical properties was observed for nano-SiO2 loading below 10 phr due to its effective role in refinement of filler dispersion state and enhancement of rubber-filler interactions. However, most of the properties were sacrificed at 15 phr nano-SiO2 loading even with respect to the control sample which emphasized the effectiveness of nano-SiO2 within an optimum loading. Moreover, nano-SiO2 at optimum loading exhibited great improvement in initial decomposition temperature about 50°C, considerable improvement in rolling resistance (more than 8%) and enhancement in wear resistance which could be crucial for tire tread manufacturers. [ABSTRACT FROM AUTHOR]