Sponge-like polypyrrole–nanofibrillated cellulose aerogels: synthesis and application

Abstract

Nowadays, materials for soft electronics are in high demand; among the different forms of conducting materials, conducting gels have become promising candidates. They provide both the electrical conductivity and mechanical flexibility, which are prerequisites for such applications. Herein, one-step facile preparation of polypyrrole–nanofibrillated cellulose (PPy–NFC) cryogels and their conversion to aerogels are reported. PPy–NFC was prepared via an in situ oxidative polymerization of pyrrole with iron(III) chloride in the presence of NFC under frozen conditions. The mechanical properties of the cryogels were improved by increasing the NFC content from 0.1 to 2 wt%. The tensile modulii of 432 kPa and 1055 kPa were achieved for cryogels and aerogels with 2 wt% of NFC, respectively. SEM micrographs of the aerogels show the formation of entangled three-dimensional porous networks with various pore sizes depending on the NFC content. Lightweight, flexible and conducting aerogels with high specific surface area (34.5–67.3 m² g⁻¹) were obtained. The conductivity of 31 S cm⁻¹ was attained when 0.7 wt% of NFC was used for cryogel preparation, which is significantly higher than conventional globular PPy. Additionally, aerogels showed improved ability to adsorb heavy metal ions (hexavalent chromium ions) from aqueous solutions owing to their high specific surface area and ion exchange properties.