Synthesis Of Functional Triblock Copolymers And Their Characterization By Electrostatic Force Microscopy

Abstract

ABA typed triblock copolymers functionalized with pyrene and terpyridine moieties were synthesized by reversible addition-fragmentation chain transfer polymerization. The terpyridine units on the polymer chain can further be functionalized by ruthenium complexes. These ruthenium complex can enhance the photosensitivity of the copolymer by broadening the optical absorption in the UV-vis region. In addition, the copolymer (Figure 1) can also function as dispersant for carbon nanotubes, as the pyrene units at both ends of the polymer chain strongly interact with the carbon nanotube surface. A stable dispersion was formed when a solution of polymer 2 in DMF was ultrasonicated with carbon nanotube. The TEM photos before (Figure 2a) and after dispersion (Figure 2b) clearly show the attachment of a layer of polymer on the surface of carbon nanotube. The resulting polymer-nanotube hybrid was characterized by electrostatic force microscopy due to the presence of charged complexes on the nanotube surface. A conductive AFM probe with applied bias at the tip was scanned over the surface of individual nanotube, confirming the presence of charged species on the surface. The enhance of photocurrent response was also measured by photoconductive atomic force microscopy. An enhancement in photocurrent response in the region between 500-650 was observed, which strongly suggested that the ruthenium complexes played a critical role in the generation of photocurrent.