The ability to control the molecular packing and nanoscale morphology of conjugated polymers is important for many of their applications. Here, we report the fabrication of well-ordered nanoarrays of conjugated polymers, based on the self-assembly of conjugated block copolymers at the air-liquid interface. We demonstrate that the self-assembly of poly(3-hexylthiophene)-block-poly(ethylene glycol) (P3HT-b-PEG) at the air-water interface leads to large-area free-standing films of well-aligned P3HT nanowires. Block copolymers with high P3HT contents (82-91%) formed well-ordered nanoarrays at the interface. The fluidic nature of the interface, block copolymer architecture, and rigid nature of P3HT were necessary for the formation of well-ordered nanostructures. The free-standing films formed at the interface can be readily transferred to arbitrary solid substrates. The P3HT-b-PEG films are integrated in field-effect transistors and show orders of magnitude higher charge carrier mobility than spin-cast films, demonstrating that the air-liquid interfacial self-assembly is an effective thin film fabrication tool for conjugated block copolymers.

The colloidal self-assembly of a new conjugated diblock copolymer of a polythiophene derivative, poly [3-(2,5,8,11tetraoxatridecanyl)thiophene]-block-poly(ethylene glycol) (PTOTTb-PEG), led to various well-defined assembly structures such as vesicles, sheets, and nanoribbons. A unique and technologically relevant nanoribbon structure with a dimension reaching tens of micrometers was formed in water when polar protic solvents were used as initial cosolvents. Self-assembly of PTOTT-b-PEG in various solvent compositions and polymer concentrations indicated that the hydrogen bonding between the diblock copolymer and the self-assembly medium plays an important role in determining the self-assembly structure and that the final assembly structure should be the result of a delicate interplay between hydrogen bonding and π−π interactions. This study demonstrates that the addition of hydrogen bonding capability and amphiphilicity in the self-assembly of conjugated polymers can lead to many interesting well-defined assembly structures that are not typically found in conjugated polymers.

We describe the synthesis and self-assembly of amphiphilic semiconducting polymers composed of a polythiophene derivative (i.e., poly [3-(2,5,8,11-tetraoxatridecanyl)thiophene] (PTOTT)) and an oligonucleotide, DNA-b-PTOTT. These new bioconjugated polymers combine the excellent optoelectronic properties of semiconducting polymers and the programmable molecular recognition properties of DNA. Because of the unique combination of rigid polythiophene and highly negatively charged DNA, they self-assemble into size-controllable vesicles in water. DNA-modified one-dimensional polythiophene nanoribbons were formed by simultaneous assembly of DNA-b-PTOTT with PEG-b-PTOTT, demonstrating that various types of DNA-modified functional nanostructures can be formed by the mixed assembly. This approach offers a new pathway to couple various types of soft optoelectronic nanostructures with DNA's molecular recognition properties.

Here, we report that long-range order, directioncontrolled, ultrathin conjugated polymer films can be formed by the self-assembly of conjugated block copolymers (i.e., poly(3hexylthiophene)-block-poly(ethylene glycol)) at inclined air−water interfaces. Structure analyses revealed well-aligned nanowire arrays of poly(3-hexylthiophene) with a dramatically increased ordered domain size compared to the polymer films formed on a flat water surface. The improved degree of order was attributed to the flow field created by the enhanced solvent evaporation at the top of the water contact line. Note that it is challenging to prepare such wellordered and molecularly thin films of conjugated polymers by conventional fabrication methods. The long-range order polymer film showed hole mobility an order of magnitude higher than polymer films formed on a flat interface when implemented as an active layer of field-effect transistor devices. This study demonstrates that a simple interface modification can significantly impact the self-assembly process, structure, and function of polymer films formed at the air−liquid interface.

Here, we report an unusual oxidation-induced photoluminescence (PL) turn-on response of a poly(3-alkoxythiophene), poly(3-{2-[2-(2-ethoxyethoxy)ethoxy]ethoxy}thiophene) (PEEEET). PEEEET shows a significantly red-shifted absorption spectrum compared to polyalkylthiophenes and is almost nonfluorescent (quantum yield ≪ 1%) in its pristine state. The introduction of sulfonyl defects along the polymer backbone by the oxidation of PEEEET with meta-chloroperbenzoic acid (m-CPBA) increased the emission quantum yield with the intensity increasing with the degree of oxidation. Molecular modeling data indicated that the oxidation-induced PL increase cannot be explained by the nature of monomer units and radiative rate changes. We attributed the enhanced fluorescence to the reduced nonradiative rate caused by the increased band gap, according to the energy gap law, which is consistent with the observed blue shifts in absorption and PL spectra accompanied by the PL increase.