Renewable chiral nematic liquid crystal template for highly ordered semiconducting polymers

The future of organic electronics relies on the ability to facilitate intra- and interchain ordering of semiconducting polymers (SPs). In this work, cellulose nanocrystals (CNCs), a material derived from biomass, was used to enhance the alignment of semiconducting polymer poly[3-(potassium-4-butanoate) thiophene-2,5-diyl] or PPBT through liquid crystal ordering. CNCs are rod-like particles that form a chiral nematic liquid crystal phase. The inclusion of these renewable particles in PPBT solutions resulted in highly birefringent domains under polarized optical microscopy, demonstrating the ability of CNCs to ``template'' PPBT into liquid crystal phases. The presence of PPBT $\pi $-$\pi $ stacks was confirmed by both a bathochromic shift as well as the position and intensity of 0-0 and 0-1 vibrational peaks in UV-Vis spectroscopy. Circular dichroism (CD) spectroscopy showed that the PPBT/CNC blends were chiral and had a pronounced negative CD peak at the $\pi $-$\pi $ stacking wavelength (578 nm), providing evidence that these stacking interactions had a helicoidal twist.