Cellulose Nanowhiskers Templating in Conductive Polymer Nanocomposites Reduces Electrical Percolation Threshold 5-Fold.

Abstract

The creation of conducting networks within composite materials is very important to reduce the generally expensive conducting polymer content, to create conducting/nonconducting domains, and to adjust conductivity of the final composite. We developed cellulose/poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) (PEDOT:PSS)-based polystyrene (PS) composites with an extremely low percolation threshold of the conductive polymer. The percolation threshold of PEDOT:PSS in PEDOT:PSS/PS blends, being 2.2 wt % (2.31 vol%), was lowered to 0.4 wt % (0.42 vol%) by adding 0.8 wt % (0.56 vol%) of cheap, nonconducting cellulose nanowhiskers. Such a low percolation threshold of PEDOT:PSS is attributed to the templating effect of the cellulose nanowhiskers: the conducting PEDOT:PSS is thought to adsorb onto the cellulose surface and by doing that (at least partly) covers the network formed by the percolating, high aspect ratio cellulose whiskers in the PS matrix. UV-vis experiments indeed point to an interaction between PEDOT:PSS and the cellulose whiskers, confirming the templating of PEDOT:PSS onto the nanowhiskers during processing and film formation. This approach can be applied to other conducting composites to reduce the required conducting polymer content and increase the ease of processing as electrical percolation is directly achieved.