Fast and Selective Post-polymerization Modification of Conjugated Polymers Using Dimethyldioxirane

Abstract

Modification of functional groups attached to conjugated polymer backbones can drastically alter the material properties. Oxidation of electron-donating thioalkyl substituents to electron-withdrawing sulfoxides or sulfones is a particularly effective modification. However, so far, this reaction has not been studied for the modification of conjugated polymers used in organic electronics. Crucial questions regarding selectivity and reaction time waited to be addressed. Here, we show that the reaction is highly selective and complete within just a few minutes when using dimethyldioxirane (DMDO) for the oxidation of thioalkyl substituents attached to the well-investigated conjugated polymers poly(9-(1-octylnonyl)carbazole-alt-4,7-dithienylbenzothiadiazole) (PCDTBT) and poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT). The selectivity was confirmed by comparison with polymers obtained from pre-oxidized monomers and by control experiments using related polymers without thioalkyl substituents. Using DMDO, the oxidation yields acetone as the only side-product, which reduces the work-up to mere evaporation of solvents and excessive reagent. Our results show that this oxidation is an exciting method for the preparation of electron-deficient conjugated polymers. It may even allow the preparation of electron acceptors for solar cells directly from the electron donors.

Postfunctionalization of a Perfluoroarene-Containing π-Conjugated Polymer via Nucleophilic Aromatic Substitution Reaction

“…Therefore, the S N Ar-based postfunctionalization of perfluoroarene-containing π-conjugated polymers would be a novel material design and worth investigation. Very recent reports revealed that the fluorine group in the fluoro-benzothiadiazole unit in a conjugated polymer main chain undergoes substitution with various thiol-nucleophiles . In the present study, the tetrafluorophenylene unit is used for the postfunctionalization, which offers more chance to introduce functionalities into the conjugated main chain.…”

Post-polymerisation approaches for the rapid modification of conjugated polymer properties

“…12 Sulfone-substituted polymers P25-31 prepared via post-polymerisation oxidation of sulfur atoms in polythiophenes and alkylthio-substituted polymers. [84][85][86][87][88] solution, no change in the absorption wavelengths was observed in this case, but the emission was red shifted by B80 nm, from blue to yellow.…”

“…In some more recent follow-up work, the use of DMDO to alter the photophysical properties of alkylthio-substituted conjugated polymers was demonstrated in donor–acceptor type materials ( P28–30 ) as well as alkylthio-substituted poly( p -phenylene vinylene)s P31 . 87,88…”

“…The first reaction -the oxidation of sulfur atoms in the backbone or in functional groups attached to the backbone to the corresponding sulfoxides or sulfones -has been shown to be a particularly fast and selective approach for post-polymerisation functionalisation of conjugated polymers. [84][85][86][87][88] The approach is especially useful to obtain polymers with significantly altered properties from a starting polymer in just one step, as the electron-donating sulfur is transformed into electron-withdrawing groups by the oxidation. Fig.…”

Diversification of Conjugated Polymers via Postpolymerization Nucleophilic Aromatic Substitution Reactions with Sulfur-, Oxygen-, and Nitrogen-Based Nucleophiles

“…S N Ar reactions using thiolates, − aryloxides, − and pyridine derivatives − as nucleophiles have been used to fabricate functional small molecules and polymeric materials. However, the use of S N Ar reactions for modifying the main chain of conjugated polymers, again, remains rare. ,,− …”