Conjugated polymers
Samson A. Jenekhea and Daoben Zhub
aUniversity of Washington, Department of Chemical Engineering, Department of Chemistry, USA
bInstitute of Chemistry, Chinese Academy of Sciences, Beijing, China
 Samson A. Jenekhe |
 Daoben Zhu |
π-Conjugated polymers – as a class of materials and a field of research – have come a long way from the breakthrough polyacetylene of 1977! They continue to be a source of innovation in electronic and photonic materials, device applications, and new technologies. They present new challenges and opportunities for contemporary polymer chemistry. This themed issue on conjugated polymers in Polymer Chemistry brings together recent results and advances in the field.
Topics covered by the collection of papers include: synthesis of conjugated polymers of various architectures; new methods for the synthesis of conjugated polymers; block conjugated copolymers; new approaches to the processing and assembly of conjugated polymers; properties of conjugated polymers, including optical, charge transport, luminescence, and photovoltaic; structure–property correlations; diverse applications of conjugated polymer semiconductors in organic electronics, optoelectronics, and photonics, including solar cells, thin film transistors, light-emitting diodes, bio-imaging, biosensors, and photonics are represented.
Unlike the polyacetylenes of the 1970s and 1980s, which were insoluble, unstable in air, and of primary interest as doped conducting materials, a new generation of air-stable polyacetylene derivatives has emerged with liquid crystalline, anisotropic optical and semiconducting properties that are promising for electronic and optoelectronic devices. The results of this resurgence of interest in the synthesis and properties of new polyacetylene derivatives are discussed in the review by San Jose and Akagi (DOI: 10.1039/c3py00063j).
New synthetic methods are crucial for advances in the preparation of conjugated polymers with evermore precise molecular architecture and tunable properties. Mario Leclerc and coworkers describe the promise and limitations of direct heteroarylation polymerization reactions in the synthesis of donor–acceptor (D–A) type conjugated polymers for organic photovoltaic applications (DOI: 10.1039/c3py21138j). The use of the aldol condensation reaction between dimethylpyrimidine and an aromatic aldehyde is exploited in the synthesis of various arylene vinylene copolymer semiconductors by Stefan, Biewer, and co-workers (DOI: 10.1039/c3py00137g). Another example of novel conjugated macromolecular structures is the series of intramolecular π-stacked conjugated polymers described by Morisaki, Chujo, and coworkers (DOI: 10.1039/c3py00607g).
The electronic and photonic properties of conjugated polymers as well as their performance in devices critically depend on the nanoscale to mesoscale organization, ordering, and orientation of the macromolecular materials in the solid state. Challenges and approaches in the self- and directed-assembly of conjugated polymers are covered by several papers in this themed issue. The reviews by Dong, Hu, and coworkers (DOI: 10.1039/c3py00131h) and Li et al. (DOI: 10.1039/c3py00098b) provide updates on recent approaches and advances in this area. The photonic properties of conjugated polymer-based nanostructures and the applications of such nanomaterials to control and manipulate the transport and dynamics of excitons and photons are covered in the review by O'Carroll et al. (DOI: 10.1039/c3py00198a). A final example here is the controlled self-assembly of block copoly(3-alkylthiophene)s in solution and films by molecular design described in a paper by Koeckelberghs et al. (DOI: 10.1039/c3py00133d).
Organic light-emitting diodes (OLEDs) for displays and solid state lighting represent one of the very successful commercial applications of organic/polymer semiconductors. Efforts aimed toward the development of next generation OLED materials are exemplified by some papers in this issue, including the synthesis and photophysical properties of polyfluorenes (DOI: 10.1039/c3py00124e) and poly(arylene ethynylene)s containing organosilicon complexes in the main chain (DOI: 10.1039/c3py00215b). The light-emitting properties of conjugated polymers and their facile molecular design for stimuli-responsiveness also make them attractive for bio-imaging and biosensor applications (DOI: 10.1039/c3py00097d, DOI: 10.1039/c3py00020f, DOI: 10.1039/c3py00123g, DOI: 10.1039/c3py21080d).
The design and synthesis of conjugated polymer semiconductors for high performance organic field-effect transistors (OFETs) are the subjects of several papers in this issue. For example, Osaka, Takimiya, and coworkers describe the direct borylation of an electron-deficient monomer and its use for the facile synthesis of high mobility D–A copolymer semiconductors (DOI: 10.1039/c3py00161j). In a similar vein, Liu, Zhang, and coworkers introduce a novel, isoindigo-inspired, electron-deficient building block and several D–A copolymers for p-channel OFETs (DOI: 10.1039/c3py00129f). A new polymer semiconductor that gives rise to air-stable p-channel OFETs is described by List, Müllen, and coworkers (DOI: 10.1039/c3py00089c) while Kai Xiao and coworkers report a water-soluble polythiophene derivative for OFETs that could be manufactured by green processing (DOI: 10.1039/c2py21020g). Arylene vinylene based D–A copolymers and their use in flexible memory devices are discussed by Wen-Chang Chen and coworkers (DOI: 10.1039/c3py00107e).
Considerable progress has recently been made in developing conjugated polymer-based organic photovoltaic devices as low cost alternatives to inorganic solar cells. However, numerous challenges remain and various approaches to addressing these problems are exemplified by the many papers in this themed issue. Most of the contributions in this area discuss new D–A copolymers that exhibit broad absorption bands, high hole mobility, and suitable frontier molecular orbital energy levels relative to fullerene derivatives, leading to efficient polymer/fullerene blend solar cells (e.g. DOI: 10.1039/c3py00121k, DOI: 10.1039/c3py00119a, DOI: 10.1039/c3py00061c, DOI: 10.1039/c3py20848f, DOI: 10.1039/c3py00143a, DOI: 10.1039/c3py00132f, DOI: 10.1039/c3py00138e). Wang, Pei, and coworkers on the other hand discuss the synthesis of n-type conjugated polymers and their use as acceptors in producing fullerene-free all-polymer solar cells (DOI: 10.1039/c3py00112a).
Finally, as Guest Editors we hope that the reader finds the collection of communications, reviews, and articles in this themed issue stimulating and a basis for further work in the ever expanding field of conjugated polymers.
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