Block Copolymers for Directional Charge Transfer: Synthesis, Characterization, and Electrochemical Properties of Redox-Active Triarylamines
摘要:
A series of styrenic triarylamines bearing electron-withdrawing or electron-donating substituents were synthesized and readily polymerized by nitroxide-mediated polymerization (NMP). The utility of the homopolymers as macroinitiators for the preparation of defined block copolymers is demonstrated. All redox-active polymers were characterized in detail by NMR, MS, and SEC measurements; in addition, their electrochemical properties were studied. The homopolymers undergo reversible oxidation, whereby the redox potential is modulated by the substitution pattern. In the case of the copolymers, the sequential oxidation of the individual blocks is observed and corroborated by (spectro)electrochemical measurements. The ratio of transferred charges per redox-active block agreed with the stoichiometric composition, as readily quantified by the semi-integral analysis of the electrochemical data. In addition, redox-titration experiments revealed effective electron transfer between the redox-active polymers following the order of their redox potentials. These results demonstrate the potential to achieve directional charge transfer in hierarchically defined block copolymers.
Nitroxide-Mediated Polymerization of Styrenic Triarylamines and Chain-End Functionalization with a Ruthenium Complex: Toward Tailored Photoredox-Active Architectures
作者:Robert Schroot、Christian Friebe、Esra Altuntas、Sarah Crotty、Michael Jäger、Ulrich S. Schubert
DOI:10.1021/ma302631f
日期:2013.3.26
The preparation of redox-active polymers and the chain-end functionalization with one ruthenium complex was investigated in detail. A series of substituted monomers, i.e., styrenic triarylamines bearing methyl, fluoro, or methoxy substituents, were prepared by a one-pot Hartwig-Buchwald coupling. The nitroxide-mediated polymerization (NMP) was studied by variation of the functional initiators, the monomer-to-initiator ratios, and the solvent. The kinetic analysis of the prototypical methyl-substituted triarylamine shows the controlled polymerization up to 75% conversion, but a considerable decrease of the polymerization rate was observed during the course of the reaction. Both chain-end functionalities of the purified oligomers were subsequently utilized, i.e., the nitroxide to serve as a macroinitiator for an additional NMP step and the chloromethyl group to introduce one ruthenium complex at the chain terminus. The products were analyzed in detail by size-exclusion chromatography, NMR spectroscopy, and mass spectrometry. The optical and electrochemical properties of the prepared poly(triarylamine)s show the application potential as charge transport materials in conjunction with the photoactive ruthenium complex.
Block Copolymers for Directional Charge Transfer: Synthesis, Characterization, and Electrochemical Properties of Redox-Active Triarylamines
作者:Robert Schroot、Ulrich S. Schubert、Michael Jäger
DOI:10.1021/acs.macromol.5b00449
日期:2015.4.14
A series of styrenic triarylamines bearing electron-withdrawing or electron-donating substituents were synthesized and readily polymerized by nitroxide-mediated polymerization (NMP). The utility of the homopolymers as macroinitiators for the preparation of defined block copolymers is demonstrated. All redox-active polymers were characterized in detail by NMR, MS, and SEC measurements; in addition, their electrochemical properties were studied. The homopolymers undergo reversible oxidation, whereby the redox potential is modulated by the substitution pattern. In the case of the copolymers, the sequential oxidation of the individual blocks is observed and corroborated by (spectro)electrochemical measurements. The ratio of transferred charges per redox-active block agreed with the stoichiometric composition, as readily quantified by the semi-integral analysis of the electrochemical data. In addition, redox-titration experiments revealed effective electron transfer between the redox-active polymers following the order of their redox potentials. These results demonstrate the potential to achieve directional charge transfer in hierarchically defined block copolymers.