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Sun H.,State University of New York at Buffalo | Sun H.,Shanghai Key Laboratory of Advanced Polymeric Materials | Autschbach J.,State University of New York at Buffalo
Journal of Chemical Theory and Computation | Year: 2014

In varying contexts, the terms "energy gap" (energy difference) or "band gap" may refer to different experimentally observable quantities or to calculated values that may or may not represent observable quantities. This work discusses various issues related to calculations of electronic energy gaps for organic π-conjugated oligomers and linear polymers by density functional theory (DFT). Numerical examples are provided, juxtaposing systematic versus fortuitous agreement of orbital energy gaps with observable fundamental (ionization vs electron attachment) or optical (electronic excitation) energy gaps. Successful applications of DFT using nonempirically tuned hybrid density functionals with range-separated exchange (RSE) for calculations of optical gaps, fundamental gaps, and electron attachment/detachment energies are demonstrated. The extent of "charge-transfer like" character in the longest-wavelength singlet electronic excitations is investigated. © 2014 American Chemical Society. Source


Xia F.,Shanghai Key Laboratory of Advanced Polymeric Materials | Xu S.A.,Shanghai Key Laboratory of Advanced Polymeric Materials
Applied Surface Science | Year: 2013

The surface of aluminum foil was treated using silane coupling agent and chromate-phosphate conversion solution respectively, then a flexible laminate consisting of five layers was prepared using polypropylene film as inner sealant layer and epoxy resin as adhesive between polypropylene film and aluminum foil. The surface morphology and composition of the foil after treatment were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and the hydrophilicity of the foil was evaluated by contact angle measurement (CAM). The adhesive strength between the aluminum foil and polypropylene film, and the heat sealing strength of polypropylene film were measured by tensile tester, their dependences on the surface treatments were further investigated. It can be concluded that the adhesive strength and heat sealing strength depend on not only the hydrophilicity, but also the morphology of the foil surface. The rough and porous surface of the treated foil can enhance both the adhesive strength and heat sealing strength. © 2012 Elsevier B.V. Source


Sun H.,State University of New York at Buffalo | Sun H.,Shanghai Key Laboratory of Advanced Polymeric Materials | Autschbach J.,State University of New York at Buffalo
ChemPhysChem | Year: 2013

Nonempirically tuned hybrid density functionals with range-separated exchange are applied to calculations of the first hyperpolarizability (β∥) and charge-transfer (CT) excitations of linear "push-pull" donor-acceptor-substituted organic molecules with extended π-conjugated bridges. An unphysical delocalization with increasing chain length in density functional calculations can be reduced significantly by enforcing an asymptotically correct exchange-correlation potential adjusted to give frontier orbital energies representing ionization potentials. The delocalization error for a number of donor-acceptor systems is quantified by calculations with fractional electron numbers and from orbital localizations. Optimally tuned hybrid variants of the PBE functional incorporating range-separated exchange can produce similar magnitudes for β ∥ as Møller-Plesset second-order perturbation (MP2) correlated calculations. Improvements are also found for CT excitation energies, with results similar to an approximate coupled-cluster model (CC2). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Wang L.,Shanghai Key Laboratory of Advanced Polymeric Materials | Lin J.,Shanghai Key Laboratory of Advanced Polymeric Materials
Soft Matter | Year: 2011

Using self-consistent field calculations, multicore micelles, such as the double-stranded superhelix, were discovered from the solution-state self-assembly of linear ABC terpolymers consisting of a solvophilic midblock and two mutually incompatible solvophobic endblocks. The multicore micelles were formed when the A and C endblocks self-associated into multiple incompatible solvophobic cores that were subdivided alternately by solvophilic B domains, thereby constructing hierarchical packing. The structures emerged depended on the relative lengths of the blocks and the solubility of the midblocks. According to the calculation results, diagrams of the observed structures as a function of the block length and midblock solubility were constructed. The results obtained can enrich our existing knowledge of the hierarchical assembly of copolymers and provide useful information for mimicking complex biological systems. © The Royal Society of Chemistry 2011. Source


Xiao Y.,Shanghai Key Laboratory of Advanced Polymeric Materials | Hu A.,Shanghai Key Laboratory of Advanced Polymeric Materials
Macromolecular Rapid Communications | Year: 2011

Bergman cyclization of enediynes, regarded as a promising strategy for anticancer drugs, now finds its own niche in the area of polymer chemistry and material science. The highly reactive aromatic diradicals generated from Bergman cyclization can undergo polymerization acting as either monomers or initiators of other vinyl monomers. The former, namely homopolymerization, leads to polyphenylenes and polynaphthalenes with excellent thermal stability, good solubility, and processability. The many remarkable properties of these aromatic polymers have further endowed them to be manufactured into carbon-rich materials, e.g., glassy carbons and carbon nanotubes. Whereas used as initiators, enediynes provide a novel resource for high molecular weight polymers with narrow polydispersities. The aromatic diradicals are also useful for introducing oligomers or polymers onto pristine carbonous nanomaterials, such as carbon nano-onions and carbon nanotubes, to improve their dispersibility in organic solvents and polymer solutions. Bergman cyclization shows great promise in polymer chemistry and material science. Diradicals generated from Bergman cyclization are used for construction of soluble polyarenes, intramolecular cross-linking linear polymer chains, initiating radical polymerization and introducing polymer onto the surface of carbon materials. Recent development in these areas is highlighted. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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