On the study of electrochromism in multiwalled carbon nanotube–polydiacetylene composites

Multiwalled carbon nanotubes (MWCNTs) have been shown to induce electrochromism in polydiacetylene (PDA) formed from the diacetylene monomer 10,12-petacosadiynoic acid (PCDA). This study investigates changes in the backbone of both partially and highly polymerized 10,12-PCDA monomers brought about by the unique electrical transport of underlying MWCNT sheets. The real time variation in absorbance with voltage revealed a clear transition from the blue to red state in both types of composites, but the Raman peaks responded differently: Raman peaks from carbon double and triple bonds in PDA did not shift under current flow in the partially polymerized composites but shifted by 21.75 and 17.85 cm−1 respectively, in the highly polymerized composites. These results suggest that stress in the PDA backbone was not crucial for forming the red phase when electrical stimulus was involved. Polarized Raman experiments revealed significant alignment changes in the composites as a result of current flow. It is proposed that a widening of PDA band gap due to π-orbital de-stacking is the principle behind electrically induced blue to red transition in MWCNT–PDA composites.