Nanocomposites based on cellulose whiskers and (semi)conducting conjugated polymers

Two examples of a new class of functional nanocomposites derived from cellulose nanofibers (referred to as whiskers'') and (semi) conducting pi-conjugated polymers were prepared and studied. The conjugated polymers used were polyaniline (PANI) and a poly(p-phenylene ethynylene) (PPE) derivative with quaternary ammonium side chains. Cellulose whiskers with a typical diameter of around 20 nm, a length of around 1-2 mm, and anionic surface charges were combined with the positively charged pi-conjugated polymers to form stable dispersions in polar solvents such as formic acid. Thin films were produced by solution-casting. Their composition was systematically varied to comprise between 65 and 99.4% w/w of the whiskers. Measurements of electrical conductivity, photoluminescence, and mechanical properties reveal that the nanocomposites synergistically combine the electronic characteristics of the conjugated polymers with the outstanding mechanical characteristics of the cellulose scaffold.