Zhishan Bo

A Planar Copolymer for High Efficiency Polymer Solar Cells

An alternating copolymer, poly(2-(5-(5,6-bis(octyloxy)-4-(thiophen-2-yl)benzo[c][1,2,5]thiadiazol-7-yl)thiophen-2-yl)-9-octyl-9H-carbazole) (HXS-1), was designed, synthesized, and used as the donor material for high efficiency polymer solar cells. The close packing of the polymer chains in the solid state was confirmed by XRD. A J(sc) of 9.6 mA/cm(2), a V(oc) of 0.81 V, an FF of 0.69, and a PCE of 5.4% were achieved with HXS-1 and [6,6]-phenyl C(71)-butyric acid methyl ester (PC(71)BM) as a bulk heterojunction active layer spin-coated from a solvent mixture of 1,2-dichlorobenzene and 1,8-diodooctane (97.5:2.5) under air mass 1.5 global (AM 1.5 G) irradiation of 100 mW/cm(2).

Dendritic Effect on Supramolecular Self-Assembly: Organogels with Strong Fluorescence Emission Induced by Aggregation†

A novel class of dumbbell-shaped dendritic molecules with a p-terphenylene core was synthesized, and their self-assembling properties were investigated. The incorporation of bulky dendritic wedges to the central stiff aromatic scaffolds could finely tune their solubility in many organic solvents. Unlike the self-assembly behavior of p-terphenylen-1,4-ylenebis(dodecanamide), the p-terphenylene cored different generation dendritic molecules could form gels in several kinds of organic solvents through a cooperative effect of the pi-pi stacking, hydrogen-bonding, and van der Waals forces. Interestingly, significant fluorescence enhancement was observed after gelation. Extensive investigations with atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), theological measurements, UV-vis absorption spectroscopy, FT-IR spectroscopy, 1H NMR, and X-ray powder diffraction (XRD) revealed that these dendritic molecules self-assembled into elastically interpenetrating one-dimensional nanostructures in organogels.

Spiro-Bridged Ladder-Type Poly(p-phenylene)s: Towards Structurally Perfect Light-Emitting Materials

Structurally perfect spiro-bridged ladder-type poly(p-phenylene)s, which show blue fluorescence in the photoluminescence (PL) and electroluminescence (EL) emission spectra, are prepared by Suzuki-Miyaura polycondensation and Friedel-Crafts cyclization. The polymers are free of ketonic defects, exhibiting excellent thermal and color stability upon annealing in air at 110 degrees C for 24 h.

Hierarchical Supramolecular Self‐Assembly of Nanotubes and Layered Sheets

Interest in tubular nanostructures has been continuously growing since the discovery of carbon nanotubes in 1991. Tubular nano-objects have displayed unique optical, electronic, and magnetic properties and have found potential use in such applications as nanodevices, catalysis, biomimetics, and energy storage. The preparation of novel high-quality nanotubes is still a challenging field of research. In contrast to inorganic and macromolecular tubules, which have been explored extensively over the last decade, low-molecular-weight organic compounds with their intrinsic merits of diversity, tailorability, and multifunctionality are good candidates for the construction of nanotubes. The supramolecular self-assembly process of mimicking nature to construct biologically active structures can generate ordered complex structures from simple building blocks. Thus, the selfassembly of nanotubes from well-defined, simple building blocks would be fascinating and practically useful. However, progress on the self-assembly of organic nanotubes from nonamphiphiles to date lags behind that of their amphiphilic counterparts, which usually follows a twisted-belt mechanism. Herein, we report the hierarchical supramolecular selfassembly of a small organic nonamphiphilic molecule, paraterphenylen-1,4’’-ylenebis(dodecanamide) (TB), to form a new kind of rolled-up organic nanotube from its nanosheet precursor. We also highlight the use of these rolled-up nanostructures as a template to fabricate composite nanotubes with C60 inside. The formation of the self-assembled nanotubes follows a similar mechanism to that proposed for the formation of multiwalled carbon nanotubes. As shown in Figure 1, TB has a central rigid terphenylene segment, two secondary amido functional groups, and two flexible alkyl chains. The unique structural feature of TB makes it an ideal candidate for self-assembling through p–p stacking and directed intermolecular hydrogen bonding. The terphenylene segment has a strong tendency to aggregate through p–p overlap. The structural feature allows TB to form a supramolecular ladder structure through intermolecular translation-related hydrogen bonding. The p–p interaction and the intermolecular hydrogen bonding have a synergistic effect on the formation of extremely stable aggregations. TBwas synthesized by Suzuki cross-coupling (Figure S1 in the Supporting Information). The strong synergistic effect of the p–p stacking and directed intermolecular hydrogen bonding made TB almost insoluble in any solvent at room temperature, thus making routine characterization impossible. TB precipitated from the solvent mixture during the reaction, but it could be completely redissolved in hot THF and precipitated after cooling, which made purification convenient. The high purity of TB was confirmed by combustion analysis. The self-assembly of TB is a solvent-mediated process. The concentration of TB in the THF solution determined the formation of the self-assembled nanotubes and/or layered sheets. A suspension of TB in THF (concentration: 0.1 mgmL ) was heated to reflux until all the solids were completely dissolved to form a colorless, clear solution. The solution was allowed to cool gradually to room temperature; it turned cloudy after about 1 h. A scanning electron microscopy (SEM) study of an air-dried suspension of TB on a silicon substrate showed the formation of fibril assemblies with a high aspect ratio (Figure 2a and Figure S3a in the Supporting Information). The open-ended feature of these fibers revealed a tubular structure (Figure 2b). Transmission electron microscopy (TEM) images showed the presence of tubes several tens of micrometers in length with an average Figure 1. Chemical structure of TB and the possible intermolecular translation-related hydrogen bonding.

STABLE SUPERHYDROPHOBIC FLUORINE CONTAINING POLYFLUORENES

Fluorene-based polymers containing perfluorooctyl moieties were designed and synthesized. The high electronegativity and F…H-C interactions are present in the fluorinated polymers, which slightly induce blue-shift of UV-Vis absorption in film. The fluoropolymer films prepared from fluorinated solvents show lager contact angles than those prepared in non-fluorinated solvents.

Synthesis of polyfluorenes bearing lateral pyreneterminated alkyl chains for dispersion of single-walled carbon nanotubes

Two kinds of polyfluorenes bearing two lateral pyrene terminated alkyl chains and two alkyl chains per repeating unit were synthesized by Suzuki polycondensation and used to disperse single-walled carbon nanotubes (SWCNT) in organic solvents. Stable polymer-SWCNT complex can be formed via the multivalent π-π stacking interaction of the lateral pyrene functional groups and the polyfluorene backbone with the outer surface of carbon nanotubes; meanwhile the lateral alkyl chains can impart good solubility to the complex. As expected, polyfluorenes bearing lateral pyrene functional groups and octyl chains exhibited much higher carbon nanotube solubility in common organic solvents than the corresponding polyfluorenes bearing only octyl chains. Photophysical studies indicated that the formation of polymer-SWCNT complex can effectively quench the fluorescence of polyfluorenes.