Polydopamine (PDA) is a biopolymer, which can form uniform thin films on almost all solid substrates as well as at the liquid/air interface. Carbonized polydopamine possesses graphite-like structure and exhibits high electrical conductivity, which makes it a potential carbon-based thin film conductor. However, studies on mechanical behavior of PDA and its derived materials are very limited. In this study, PDA samples were synthesized through self-assembly of dopamine in aqueous solution. Elastic modulus of thin films was measured using the nanoindentation technique. It is shown that the Young’s modulus of PDA thin film increased with increasing heat treatment temperature (up to 600°C). Doping with Cu ions also increased the Young’s modulus of PDA. Furthermore, all PDA thin films, with and without Cu, exhibited creep behavior.
Two-dimensional (2D) conducting polymers are expected to offer emergent topological, structural, and physical properties, which has become the "holy grail" for the development of plastic electronics. Here, we report the assembly of a free-floating metallic polymer layer, consisting of poly(3,4-ethylenedioxythiophene) complexed with poly(styrenesulfonate) anions, directed by electrostatic recognition, amphiphilicity, and aromatic interactions. The obtained large-area crystalline nanosheets exhibit excellent environmental stability and mechanical robustness, meanwhile showing an electrical conductivity of 1216 S·cm, the highest among the nanometer-thick conducting polymers. The kirigami-inspired freestanding polymer thermoelectrics, repeatedly stretching up to 200% strain, is demonstrated with high Seebeck coefficient with an optimized power factor of 95 μW m K. The large-scale assembly and aqueous compatibility of 2D conducting polymers provide an exciting platform for integrating thermoelectricity into free-floating polymer nanostructures.
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