Fluorescent conjugated polycarbazoles for explosives detection: Side chain effects on TNT sensor sensitivity

Considering electronic and structural interactions between fluorescent polymers and TNT, we have designed and synthesized two carbazole-based polymers (P1 and P2), possessing 2-ethylhexyl and 4-[tris-(4-octyloxyphenyl)methyl]phenyl as side chains, respectively. The distinct side chains cause dramatic differences in the polymer sensing behavior. It is demonstrated that large and more rigid side chains could reduce the interactions between polymer chains in the solid state, while supporting the diffusion of explosives through more accessible space, thereby contributing to the sensitivity. Furthermore, we have proved that bulky side chains obviously did not influence the conformation of the backbone, which is necessary for the conjugated polymers to act as fluorescent sensing material. The results suggest that P2 is a promising material for TNT detection with pronounced sensitivity, in addition they provide a new design-thought for TNT sensing materials.