Reports: AC7
45853-AC7 Electropolymerizable Dendrons in Reversible Addition Fragmentation Chain-Transfer (RAFT) Polymerizations: Electrochemical Behavior and Macromolecular Assemblies
The Advincula group has investigated and reported a new series of electropolymerizable dendritic-linear block copolymers based on the combination of polybenzylether dendrons and linear polymers prepared by RAFT or grafted with pre-existing polymers by end-group coupling. The morphologies (mesophase and nanophase), solution self-assembly, monolayer formation, and electro-optical properties were investigated. The main hypothesis is that the introduction of electro-optical properties in these unique dendron block copolymer systems and their resulting mesophases will also result in new electrochemical methodologies for polymer thin film processing. In particular, the dendrons incorporating the electropolymerizable monomeric units have been a key design feature. By incorporating electrochemically active side groups on unique macromolecule topologies, it was possible to introduce new concepts in macromolecular self-assemblies and electrochemical processing. The dendron with a high concentration of the electroactive monomer group was utilized both for cross-linking and controlled electrodeposition. The linear block was typically synthesized systematically by reversible addition-fragmentation chain transfer (RAFT) polymerization using electroactive monomer-functionalized dendritic chain transfer agents (CTA)s, a type of macroinitiator. Characterization of the macromolecules was done by GPC, MALDI, NMR, DSC, and TGA to determine structure-property relationships as a function of dendron-generation and linear polymer block characteristics. The dendritic CTA generation in particular proved to be an important in precursor polymer with electropolymerizability observed as a function of dendritic generation. Different electroactive monomers such as carbazole, terthiophene, etc have been reported and tethered to the dendron or the linear block. Amphiphilicity to form micelles and solution self-assembly towards supramolecular architectures is currently under study with various ratios of hydrophilic and hydrophobic linear-dendron blocks. An important continuing direction in the study involved a systematic electrochemical investigation of block copolymer thin films and Langmuir-Blodgett self-assembly on conducting substrates. The electrodeposition kinetics and viscoelastic properties are being studied by in-situ measurements based on quartz crystal microbalance (QCM) and surface plasmon resonance (SPR) spectroscopy. Other techniques including FT-IR, atomic force microscopy (AFM) and ellipsometry have been utilized to analyze these films. TEM, SEM, and SAXS are currently being considered to investigate block-copolymer morphologies (mesophases) and micellar assemblies. The publications include works already reported in Macromolecules, Langmuir, Advanced Functional Materials, and J. of American Chemical Society. Other publications are still in preparation.
