Synthesis of block copolymer-carbon nanotube composites and study of photo-induced electron transfer processes

Abstract

Homopolymer and block copolymers functionalized with pyrenylcarbazole moieties were synthesized by reverse-addition-fragmentation chain transfer polymerization (RAFT). The pyrenylcarbazole units exhibit strong p-p interaction with carbon nanotube (CNT) surface such that the polymers can function as dispersing agent for CNTs in various solvents. Terpyridine units were incorporated into another block, which was further converted to different photosensitizing ruthenium complexes. Ultrafast photophysical measurements were performed on the homopolymer. Upon attaching on CNT surface, significant change in the excited state properties of pyrenylcarbazole was observed. Femtosecond transient absorption spectroscopy measurements showed that the decay of the pyrenylcarbazole excited states was much faster compared to those of CNT-free polymer. This is attributed to a photo-induced electron transfer between the pyrenylcarbazole units and CNT. By coupling with different photosensitizing molecules, the resulting CNT composites are promising candidates for photo/chemical sensing applications.