Conjugated Block Copolymers for Functional Nanostructures

Conspectus Conjugated polymers have been actively studied as an alternative to inorganic semiconductors for their unique optical and electrical properties and low-cost solution processability. However, typical conjugated polymer films contain numerous defects that negatively affect their transport p...

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Veröffentlicht in:Accounts of chemical research 2022-08, Vol.55 (16), p.2224-2234
Hauptverfasser: Kang, Seulki, Kim, Ga-Hyun, Park, So-Jung
Format: Artikel
Sprache:eng
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Zusammenfassung:Conspectus Conjugated polymers have been actively studied as an alternative to inorganic semiconductors for their unique optical and electrical properties and low-cost solution processability. However, typical conjugated polymer films contain numerous defects that negatively affect their transport properties, which remains a major issue despite much effort to develop ways to improve the molecular packing structure. In principle, conjugated block copolymers (BCPs) composed of a rod-type conjugated polymer and a coil-type insulating polymer can assemble into various types of ordered nanostructures based on the microphase segregation of two polymer blocks. However, such assembly typically requires a relatively large volume fraction of the coil block or modification of the rod block, both of which tend to impede charge transport. As an alternative, we and others have fabricated nanoscale assemblies of conjugated BCPs via solution-phase self-assembly, which can be used as building blocks for construction of extended nanoarrays of conjugated polymers. In particular, BCPs containing poly­(3-hexylthiophene) (P3HT), a conjugated polymer widely used for its high hole mobility, form highly ordered and technologically relevant one-dimensional (1D) nanowires with controlled lengths. A range of well-defined assembly structures such as square plates, ribbons, vesicles, and helices have been prepared from various conjugated BCPs, resembling those of peptide self-assembly, forming diverse nanostructures through combinations of π–π stacking, hydrogen bonding, and hydrophobic interactions. When the self-assembly of P3HT BCPs takes place at an air–water interface, the initially formed polymer nanowires further assemble into hierarchical two-dimensional (2D) nanoarrays with solvent evaporation. The fluidic nature of the water subphase allows fabrication of highly ordered assembly structures from P3HT BCPs with high P3HT content. The ultrathin free-standing film integrated in a field effect transistor (FET) showed orders of magnitude higher current and hole mobility compared to that fabricated by conventional spin-coating. Furthermore, binary self-assembly of a P3HT BCP and quantum dots (QDs) at the air–water interface generates well-ordered 2D films of alternating P3HT nanowires and 1D QD arrays. Unlike coil–coil BCP systems, QDs reside at the interface between P3HT and coil blocks for a broad range of QD sizes due to the strong P3HT packing interactions and the flexible water
ISSN:0001-4842
1520-4898
DOI:10.1021/acs.accounts.2c00244