Silver nanowires (AgNWs) with low sheet resistances are excellent potential candidates for high‐performance wearable electrothermal heaters operated through Joule heating. However, the thermal oxidation and electrical instability of AgNWs caused by high contact resistance and poor adhesion to different substrates considerably limit their use in devices. Graphene is used in a AgNW/graphene hybrid owing to its low oxygen permeability, lower contact resistance with AgNWs, and good van der Waals interactions. Molecular‐level contacts between AgNWs and graphene must be achieved to maximize the synergy of these properties. In this study, a multifunctional polymer possessing styrene sulfonate‐based copolymer and disulfide groups is designed; these groups allow the simultaneous dispersion of AgNWs and graphene in an aqueous solution through self‐assembly. Since this polymer promotes molecular‐level contact between AgNWs and graphene, the oxidation and Joule‐heating stabilities of the hybrid dramatically increase. In addition, a freestanding AgNW/graphene film is readily prepared, exhibiting good attachable properties on various substrates and superior stability under harsh conditions (85 °C and 85% relative humidity for 7 days). The AgNW/graphene hybrid film displays a low sheet resistance (0.36 ± 0.02 Ω sq−1) with good performance as a high‐performance electrothermal heater (200 °C at 1.5 V).
A novel method for controlling reduced graphene oxide (rGO) wrinkles through a phase transition in a solution using a low critical solution temperature (LCST) polymer dispersant has been developed. The polymer dispersant is designed by control of architecture and composition using reversible addition-fragmentation chain transfer polymerization. Synthesized poly(2-(dimethylaminoethyl) methacrylate-block-styrene) (PDbS) can be successfully functionalized on the rGO surface via noncovalent functionalization. PDbS-functionalized rGO (PDbS-rGO) exhibits good dispersibility in an aqueous phase at room temperature and forms wrinkles on the PDbS-rGO surface because of phase transition at the LCST of the polymer dispersant. The formation of PDbS-rGO wrinkles is controlled by varying the aggregation number of the polymer dispersant on the PDbS-rGO surface that strongly depends on temperature. This is confirmed by transmission electron microscopy, scanning electron microscopy, and Raman spectroscopy (I D' /I G ratios are 0.560, 0.579, and 0.684, which correspond to 45, 70, and 95 °C, respectively). In addition, the mechanism of wrinkle control is proved by gold nanoparticles that are grown in polymer dispersant on the PDbS-rGO surface.
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