Synthesis of functionalized conjugated polymers for creating cellulose/CP hybrid materialsAsaminew Yerango (asaminew.yerango.shimolo@liu.se), Bernhard Burtscher (bernhard.burtscher@liu.se), Xenofon Strakosas (xenofon.strakosas@liu.se), Renee Kroon (renee.kroon@liu.se)

Abstract 
Blending conjugated polymers (CPs) with cellulose is a promising approach to enhance their properties and create composite materials with properties that are greater than the sum of their separate components. To combine these materials, a common processing solvent is necessary to create an intimate mixing of CP’s and cellulose, or to deposit CPs onto a cellulose substrate. However, the design of CPs still often permits processing from toxic solvents, whereas the ubiquitous functionalization of CPs with sulfonate functional groups typically requires a post-processing crosslinking step to ensure stability against use in aqueous environments such as OECT’s, energy storage or electroactive fibers. In this regard, we synthesized a carboxylate-functionalized polar polythiophene (Pg4CAT) that combines water-processability with robust, reversible, and benign chemical fixation. Preliminary results from OECTs fabricated with the pure polymer PG4CAT reveal its potential for bioelectronic applications.  However, these OECT’s exhibited slow switching times and low ion conductivity. To address these issues and improve device performance, we leveraged the water processability of the materials to co-process with 15 % carboxylate cellulose nanofibrils (CNFs), to improve ion conductivity. Devices fabricated with the polymer/CNF composite ink demonstrated fast switching times, enhanced volumetric capacitance and transconductance, which demonstrates the synergy between CPs and cellulose materials.