Conjugated triblock copolymers containing both electron-donor and electron-acceptor blocks

We report a straightforward two-step synthesis toward conjugated DAD-type triblock copolymers with both electron-donor ( D) and electron-acceptor ( A) blocks. Cyano-substituted poly( phenylenevinylene) (CN-PPV) prepolymers with two bromide end groups hereby act as the central electron-acceptor building block and are generated under Yamamoto conditions. The dibromo prepolymers are finally coupled with monobromo-terminated regioregular poly(3-hexylthiophene) (P3HT), which is selected as the electron-donor block ( D). The molecular weight of the different blocks, especially the acceptor block, can be controlled by adjusting the polymerization time and the substitution pattern ( degree of alkyl substitution) of the monomers. Elemental analysis, NMR, DSC, and optical spectroscopy prove that the DAD conjugated triblock copolymers. Atomic force microscopy (AFM) images of one triblock copolymer (P3HT1-HCNPPV-P3HT1) exhibit the formation of regular nanosized mesostructures in thin films. The resulting conjugated triblock copolymer shows a distinctly different morphology as compared to a corresponding polymer blend. A covalent connection of donor ( P3HT) and acceptor (CN-PPV) blocks is a favorable way to control the scale length of nanostructure formation.