Soluble salt-driven matrix swelling of a block copolymer for rapid fabrication of a conductive elastomer toward highly stretchable electronics

A simple soluble salt-driven matrix swelling method was developed for fast fabrication of a silver nanoparticle-based conductive elastomer. Taking advantage of the synergistic effects of silver trifluoroacetate and methanol, the swelling capability of an elastomeric block copolymer polystyrene-block-polyisoprene-block-polystyrene (SIS) was greatly enhanced. The interaction of silver ions and double bonds of the copolymer enables fast infiltration of soluble salt into the polymer network, resulting in a high-content loading of silver ions, which is a prerequisite for fabrication of a highly conductive polymer. In-situ reduction was performed under a swollen state to allow the reducer to effectively penetrate into the polymer matrix, thoroughly reducing the silver salt into silver nanoparticles. A three-layered conductive elastomer was obtained, with a high concentration of silver nanoparticles formed on both surfaces of SIS copolymer. Typically, the conductivity of the reduced SIS elastomer was measured to be >2 × 10⁵ S/m when ε = 0, and can maintain to be over one seventh of its initial value even at a 200% elongation. The conductive elastomer can withstand over 1000 stretch-release cycles under a strain of 100%. A radio-frequency antenna was prepared with the conductive elastomer, which gives the ability of dimension tuning, to realize high-quality frequency-selective radiation at a wide bandwidth of larger than 2.6 GHz.