End-group functionalization of regioregular head-to-tail poly(3-alkylthiophenes) and its application to the synthesis of well-defined rod-coil block copolymers: Tuning the self-assembly and functional properties of conducting polymers

The ability to control the structure, properties and function of conjugated polymers remains a critical subject in the development of new advanced materials. Since block copolymers exhibit a wide variety of phase behaviors, synthesis of block copolymers containing π-conjugated blocks is a promising method toward controlling the self-assembly, film morphology, and hence the mechanical, electronic and optical properties of the conjugated polymers. Therefore, the major goal of this thesis is to explore the synthesis of block copolymers containing regioregular head-to-tail poly(3-alkylthiophenes) (HT-PATs), which is an important class of conducting polymers with excellent charge mobility and even superconductivity, and investigate the ability to control the nanoscale structures of these conducting species.; Our incorporation of HT-PATs into block copolymers began from the synthesis of end-group functionalized HT-PATs. These telechelic HT-PATs were then used to prepare block copolymers.; In order to monitor the end group functionalization accurately, MALDI-TOF MS characterization of PATs has been fully investigated. After matrix optimization and ionization mechanism investigation, we found that MALDI-TOF is a powerful tool to characterize the PAT system. It can not only measure the molecular weights and confirm the structures of PATs, but also monitor the end group composition of PATs. The detail of MALDI analysis of PATs is discussed in Chapter 2.; We have performed post-polymerization modification of HT-PATs and incorporated functional groups, such as –OH and –NH₂, into the polymer chain ends. These post-polymerization functionalization are presented in Chapter 3. In addition to this post-polymerization method, in-situ polymerization methods have also been investigated to incorporate functional groups to the ω ends of PATs. MALDI MS and NMR were intensively employed to obtain the end group information. These end group analyses have led to a new insight into the mechanism of nickel catalysis in the cross coupling polycondensation. This is discussed in Chapter 4.; Using the end-groups as the reactive functional polymer ends, we have prepared well-defined diblock and triblock copolymers containing HT-PATs using ATRP methods. Both AFM and TEM showed that the HT-PAT blocks in these well-defined block copolymers tend to self-assembly and form “nanowire” domains. X-ray diffraction indicates the polythiophene nanowires have layered lamella structure in their cores. Worm-like “nanowire” networks are proposed to account for the high conductivity of our block copolymers. Moreover, simply changing the solvent or evaporation conditions allows us to control the nanowire formation and the electrical conductivity of the block copolymers. Chapter 5 presents the synthesis and characterization of the block copolymers in detail.