Synthesis of Poly(3-alkylthiophene) and Phase Behavior of Polymer Blends and Block Copolymers Containing Poly(3-alkylthiophene)

Abstract

Poly(3-alkylthiophene) (P3AT) was one of the most intensive and extensive studied conducting polymer. In this study, we demonstrated the synthesis of various types of P3ATs which are as alkyl side chain length, end functionality, and block copolymers with other polymers, and also investigated their phase behavior and photovoltaic performance. In Chapter 1, basic information about P3AT was introduced. Among the synthetic methods of P3AT, regioregular P3AT was only polymerized by GRIM method. It was also possible to control the end group of polymer by using a modified GRIM method. Therefore, that reaction is fundamental in this work. In Chapter 2, phase behavior of P3HT/PS blend was investigated. All of the P3AT/PS blends exhibited UCST type phase behavior. The UCST was not simply increased (or decreased) with the length of alkyl side chain of P3AT. The miscibility of P3HT/PS blend became the least, while the P3DDT/PS blend showed the best miscibility among the four P3AT/PS pairs. This interesting phase behavior was successfully rationalized by the combination of Monte Carlo and molecular dynamics simulation.In Chapter 3, we demonstrated a new P3HT macroinitiator to a high purity P3HT diblock copolymer. The traditional P3HT macroinitiator always has a part of impurity during preparation. We prepared a new P3HT macroinitiator which have phenyl end group instead of bromine at the opposite side of ATRP fragment, and demonstrated a high purity polymerization of P3HT-b-PMA block copolymer.In Chapter 4, we presented the synthesis of various end functional P3HT from hydrophilic (hydroxyl group, -OH) to hydrophobic (perfluoroalkyl, -CF3), and their organic photovoltaic performance with PCBM. In P3HT-CF3/PCBM blend, the miscibility between them was enhanced, and the morphology of them became improved. In result, a rather high efficiency was achieved in organic photovoltaic.In Chapter 5, we introduced a fluorinated alkyl side chain in P3AT and prepared a block copolymer with P3HT for an all-conjugated block copolymer. Properties of P3FOT (solubility in organic solvent, optical property, and reactivity) were totally different from those of P3AT, but those of P3smFOT were similar with those of P3AT. Due to a lack of reactivity of P3FOT, P3HT-b-P3smFOT was only polymerized. By CV measurement, HOMO/LUMO of P3FOT and P3smFOT were figured out to be shifted to lower region as 0.2 ~ 0.4 eV compared with that of P3HT. This fluorinated thiophene polymer and its block copolymer are expected for further studies.