Strengthened, conductivity-tunable, and low solvent-sensitive flexible conductive rubber films with a Zn2+-crosslinked one-body segregated network

Abstract

A high-performance flexible conductive material based on cheap carboxymethyl chitosan (CMCS) and carboxylated styrene-butadiene rubber (XSBR) was fabricated via latex film-forming technique. Nano zinc oxide (ZnO) was introduced to react with CMCS, generating a Zn2+-crosslinked CMCS one-body segregated (Zn2+-COBS) network. Differing from reported conductive fillers with segregated structures, this Zn2+-COBS network was a continuous framework structure, which could be turned into conducting network by absorbing moisture. Superior tensile strength of 22.6 MPa was achieved with 30 wt% CMCS and 2.5 wt% ZnO owing to the “reinforced concrete structure” effect of Zn2+-COBS architecture. The order of volume resistance (Rv) of the films could be tailored between × 108 and × 104 Ω cm by changing the water content from 0 to ~20%, although at 20% water content the strength decreased to about 2 MPa. Particularly, the material with 30 wt% CMCS and 2.5 wt% ZnO achieved a Rv of 7.8 × 103 Ω cm with 18.7% water content. Thanks to the abundant hydrogen bonding interactions between CMCS chains, this special architecture provided a strong swelling restriction on the rubber matrix and dramatically improved the conducting stability of film in solvents. The Rt/R0 in toluene, petroleum ether and anhydrous alcohol for 2 h were only 7.52, 1.35 and 1.47 for the films with a water content of 4.9%, 5.3% and 8.8%, respectively. These results demonstrate a promising method to fabricate an economical, conductivity-tunable, and flexural film material with potential applications in humidity detectors or in solvent environments.