Energy transfer through heterogeneous dyes‐substituted fluorene‐containing alternating copolymers and their dual‐emission properties in the films

We report synthesis of the modified fluorene polymers tethered to the heterogeneous types of the fluorescent dyes at the cardo carbon for obtaining the dual‐emissive solid materials. A series of the alternating fluorene copolymers modified with pyrene or 9,10‐diphenylanthracene and BODIPY at the cardo carbon based on the red‐emissive donor–acceptor structure were prepared, and their characteristics were examined. From the measurements of the optical properties, the energy transfer efficiencies were evaluated. In summary, variable energy transfer efficiencies were observed between the side chains and from the side chain to the main chain. It was indicated that the energy transfer efficiencies were strongly depended on the types of the energy donor and the detection conditions as such in the solution or film. Furthermore, it was found that the cardo fluorene units can contribute to the suppression of the energy transfer in the condensed state. Finally, the dual‐emissive polymers were obtained in the film states. This is the first example, to the best of our knowledge, not only to offer systematic information on the energy transfer between the dye molecules and the polymer main‐chains via the cardo structure but also to demonstrate the polymer‐based optical materials with the dual‐emission properties. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2026–2035     

The mechanical and electrical properties of carbon nanotube‐grafted polyimide nanocomposites

Polyimide (PI)‐based nanocomposites containing aminophenyl functionalized multiwalled carbon nanotubes (AP‐MWCNTs) obtained through a diazonium salt reaction was successfully prepared by in situ polymerization. PI composites with different loadings of AP‐MWCNTs were fabricated by the thermal conversion of poly(amic acid) (PAA)/AP‐MWCNTs. The mechanical and electrical properties of the AP‐MWCNTs/PI composites were improved compared with those of pure PI due to the homogeneous dispersion of AP‐MWCNTs and the strong interfacial covalent bonds between AP‐MWNTs and the PI matrix. The conductivity of AP‐MWNTs/PI composites (5:95 w/w) was 9.32 × 10^?1 S/cm which was about 10¹⁵ times higher than that of Pure PI. The tensile strength and tensile modules of the AP‐MWCNTs/PI composites with 0.5 wt % of AP‐MWCNTs were increased by about 77% (316.9 ± 10.5 MPa) and 25% (8.30 ± 1.10 GPa) compared to those of pure PI, respectively. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 960–966     

Ab initio molecular orbital calculations of the infrared spectra of hydrogen-bonded complexes of water,ammonia and hydroxylamine

Summary The geometries of three hydrogen-bonded dimers of hydroxylamine have been optimized, at the MP2 level of theory, using the 6-31G** basis set. These calculations yielded three separate local minima on the dimer potential energy surface. The interaction energies of these three species have been calculated, and corrected for basis set superposition error. The infrared band wavenumbers and intensities have been computed, and the monomer-dimer wavenumber shifts and intensity enhancements rationalized in terms of the types and strengths of hydrogen bonds present. The predicted wavenumbers have been correlated with those measured in a recent matrix isolation spectroscopic study, and an argument for the structure of the preferred dimer has been presented.     

Ghost fluid method for strong shock impacting on material interface

It is found that the original ghost fluid method (GFM) as put forth by Fedkiw et al. [J. Comp. Phys. 152 (1999) 457] does not work consistently and efficiently using isentropic fix when applied to a strong shock impacting on a material interface. In this work, the causes for such inapplicability of the original GFM are analysed and a modified GFM is proposed and developed for greater robustness and consistency. Numerical tests also show that the modified GFM has the property of reduced conservation error and is less problem-related.     

Density nonlinearities and a field theory for the dynamics of simple fluids

We study the role of the Jacobian arising from a constraint enforcing the nonlinear relationg=V, where ,g, andV are the mass density, the momentum density, and the local velocity field, respectively, in the field-theoretic formulation of the nonlinear fluctuating hydrodynamics of simple fluids. By investigating the Jacobian directly and by developing a field-theoretic formulation without the constraint, we find that no changes in dynamics result as compared to the previous formulation developed by Das and Mazenko (DM). In particular, the cutoff mechanism discovered by DM is shown to be a consequence of the 1/ nonlinearity in the problem, not of the constraint. The consequences of this result for the static properties of the system are also discussed.     

Adhesion of Pseudomonas fluorescens on magnetic surfaces

The adhesion of Pseudomonas fluorescens (ATCC 700830) to perpendicularly polarized magnetic surfaces was recently discovered. The findings have found that the magnetic free surfaces from different magnetic polarities have different profound effects on the P. fluorescens bacterial adhesion to its surfaces. These phenomena can be explained by the surface magnetic effect, which was found to affect the surface free energy. An in situ experiment, by contrast microscopy and under static conditions, was conducted to determine the influence of magnetic surfaces, that are polarized under different external magnetizing field strengths, on bacterial adhesion. The effect of different magnetic polarities on the surface free energy has also been investigated.