The synthesis and purification of amphiphilic conjugated donor–acceptor block copolymers

Abstract

Nanoscale domains of donor and acceptor materials are crucial for charge generation in organic photovoltaic devices. These domains are difficult to achieve reproducibly in blended materials, but could be engineered into single-material active layers composed of donor–acceptor block copolymers (BCPs). In this work, we report the synthesis and purification of two novel fully conjugated BCPs, P3HT-b-PFTEGTBT and P3HT-b-PFTEGT6BT. To enhance phase separation and self-assembly, these two polymers incorporate tetraethylene glycol side chains into the PFTBT acceptor block, generating an amphiphilic system. The chemical disparity of the donor and acceptor blocks allowed the development of a purification strategy capable of isolating the desired BCP from homopolymer contaminants. This is a significant improvement over previous systems in which homopolymer contaminants can dominate the reaction mixture, affecting performance and morphology. We show that preliminary morphological analysis indicates spontaneous phase separation in thin films, demonstrating the efficacy of this design strategy and the potential application of these materials in organic photovoltaic devices. Hydrophilic tetraethylene glycol moieties are incorporated into the electron-accepting block of a donor–acceptor block copolymer (BCP) to afford two novel amphiphilic materials based on the P3HT-b-PFTBT scaffold. These amphiphilic BCPs are designed to provide enhanced morphological control as organic photovoltaic active layer materials. The chemical disparity introduced by the hydrophilic side chains enabled the design of a purification system capable of isolating the BCP product, an advantage over previously reported systems.