Nanocellulose-templated assembly of polyaniline in natural rubber-based hybrid elastomers toward flexible electronic conductors

Abstract

The wide-ranging applications of electroconductive elastomers in next-generation soft electronics demand more renewable bio-based materials derived from natural forest crops than the non-sustainable materials currently available. However, it still remains a critical challenge to construct an effective, stable and continuous conductive network in a non-conductive elastomer matrix with enhanced mechanical properties and desired electrochemical performances especially using natural polymer. Here, we report a novel type of electroconductive hybrid elastomers based on a natural rubber (NR) matrix and nanostructured CNF-PANI (cellulose nanofibers-polyaniline) complexes that synergizes the conductive nature of PANI and the biotemplate role of CNFs. The CNF-PANI complexes with ideal dispersity and high aspect ratio are synthesized through in situ oxidative polymerization of aniline monomers on the surface of CNF templates, which are further uniformly dispersed into NR latex to synthesize CNF-PANI/NR elastomers with a hierarchical 3D network structure through a latex cocoagulation process. The incorporation of sustainable and biodegradable CNFs can not only built a reinforcing network, but also support the hierarchical 3D conductive network in NR matrix. The final bio-based elastomers with a homogeneous texture exhibited intrinsic flexibility, enhanced mechanical properties (tensile strength up to 9.7 MPa, Young’s modulus up to 10.9 MPa), decent stretchability (elongation at break up to 511%), low density (∼1.16 g cm−3) and ideal conductivity (up to 8.95 × 10-1 S m-1). The highly sensitive and repeatable strain-sensor integrated by the elastomer with 8 phr of PANI could monitor the real-time motion of human body. The specific capacitance of elastomer-based electrode with 20 phr of PANI can reach up to 110 F g-1 at a current density of 0.3 A g-1, and its capacitance degradation is less than 22% after 1200 cycles, exhibiting promising electrochemical properties. The multifunctional elastomers synthesized through a facile, scalable and green approach in this work promotes the advanced applications of bio-based materials including CNFs and NR in prospective soft electronics, such as strain sensors and flexible electrodes.