Self-assembly of rod-coil block copolymers for photovoltaic applications

Two different approaches to obtain electron donor-acceptor interfaces via self-assembly of block copolymer systems are discussed, where the donor domains are formed by a pi-conjugated rod-like polymer and the acceptor domains result from a coiled polymer modified by C(60) fullerenes. in the first strategy, C(60) is chemically grafted onto the coil polymer, typically a statistical copolymer of styrene and chloromethyl styrene. This has as major effect the increase in molecular weight and volume fraction of the coil block, which can markedly perturb the self-assembled block copolymer final morphologies and eventually suppress any microseparated nanostructure in favour of fully isotropic homogeneous phases. We discuss how the presence of free homopolymer rods in the system can help recovering a microphase separated morphology suitable for photovoltaic applications. In the second approach we discuss the poly(diethylhexyl-p-phenylenevinylene-b-4-vinylpyridine) (PPV-P4VP) rod-coil block copolymer system and we argue how supramolecular interactions among P4VP and free C(60) can be exploited to blend rod-coil block copolymers and C(60) preserving the original lamellar phase.