Effects of ionic liquid on the hydroxylpropylmethyl cellulose (HPMC) solid polymer electrolyte

Biodegradable solid polymer electrolyte (SPE) is prepared by solution-casting technique using low-cost cellulose derivative, hydroxypropylmethyl cellulose (HPMC) as a host polymer. Owing to the hydrophobic nature of this polymer, it is predicted to exhibit low ionic conductivity upon addition of magnesium trifluoromethanesulfonate (MgTf₂) salt. Therefore, ionic liquid (IL), 1-butyl-3-methylimidazolium trifluoromethanesulfonate (BMIMTf), is added in order to enhance its ionic conductivity. Based on the findings, the ionic conductivity at room temperature and the dielectric behaviors of the SPE complex improved upon incorporation of 40 wt.% IL. On top of that, addition of IL reduces the degree of crystallinity and the glass transition temperature (T _g ) of the SPE. The conductivity-temperature plot revealed that the transportation of ions in these films obey Arrhenius theory. The interaction between SPE complex, MgTf₂ salt, and BMIMTf is investigated by means of Fourier transform infrared (FTIR) spectroscopy through the change in peak intensity around 3413, 1570, and 1060 cm^?1, which are responsible for –OH stretching band, C–C and C–N bending modes of cyclic BMIM⁺, and C–O–C stretching band, respectively.     

Hydrostatic pressure effect on the phase transitions of a closed-loop type block copolymer by using 2D FTIR correlation spectroscopy

The effect of hydrostatic pressure (P) on the phase transitions of polystyrene-block-poly(n-pentyl methacrylate) copolymer [PS-b-PnPMA] was investigated with FTIR spectroscopy at various temperatures. The experiments were performed by using a specially designed pressure cell optimized for low-pressure regime (<100 bar) with a higher resolution ( approximately 1 bar). The size of the closed loop consisting of both the lower disorder-to-order transition (LDOT) and the upper order-to-disorder transition (UODT) measured by FTIR spectroscopy becomes smaller with increasing P, consistent with results obtained from birefringence measurement. At lower temperatures with increasing P, the PS main chains are found to move before the PnPMA main chains. This is because the mobility of the PnPMA main chains is restricted due to the cluster formation of the alkyl side chain. At higher temperatures, the PnPMA block chains are more mobile than the PS block chains due to their larger specific volumes. The results indicate that the LDOT is mainly affected by a favorable directional interaction between PS and PnPMA blocks due to the cluster formation of the alkyl side chain, whereas the UODT depends on the combinatorial entropy.     

UV-driven switching of chain orientation and liquid crystal alignment in nanoscale thin films of a novel polyimide bearing stilbene moieties in the backbone

A novel photosensitive polyimide, poly(4,4'-stilbenylene 4,4'-oxidiphthalimide) (ODPA-Stilbene PSPI) was newly synthesized. The most surprising feature of this PSPI is that the PSPI films irradiated with linear polarized ultraviolet light (LPUVL) can favorably induce a unidirectional alignment of liquid crystals (LCs) in contact with the film surface and further switch the director of the unidirectionally aligned LCs from a perpendicular direction to a parallel direction with respect to the polarization direction of LPUVL by simply controlling the exposure dose in the irradiation process. These LPUVL-irradiated films were found to provide high anchoring energy to LCs, always giving very stable, homogeneous cells with unidirectionally aligned LCs regardless of the LC alignment directions. In the films, the PSPI polymer chains were found to undergo favorably unidirectional orientation via a specific orientation sequence of the polymer chain segments led by the directionally selective trans-cis photoisomerization of the stilbene chromophore units in the backbone induced by LPUVL exposure. Such unidirectionally oriented polymer chains of the films induce alignment of the LCs along the orientation direction of the polymer chains via favorable anisotropic molecular interactions between the oriented polymer chain segments and the LC molecules. In addition, the PSPI has an excellent film formation processibility; good quality PSPI thin films with a smooth surface are easily produced by simple spin-coating of the soluble poly(amic acid) precursor and subsequent thermal imidization process. In summary, this new PSPI is the promising LC alignment layer candidate with rubbing-free processing for the production of advanced LC display devices, including LC display televisions with large display areas.     

Scattering Operators for Matrix Zakharov-Shabat Systems

In this article the scattering matrix pertaining to the defocusing matrix Zakharov-Shabat system on the line is related to the scattering operator arising from time-dependent scattering theory. Further, the scattering data allowing for a unique retrieval of the potential in the defocusing matrix Zakharov-Shabat system are characterized. The research leading to this article was supported in part by the Italian Ministery of Education and Research (MIUR) under PRIN grant no. 2006017542-003, and by INdAM. One of the authors (CvdM) wishes to express his gratitude for the hospitality of the Department of Mathematics of the University of Texas at Arlington during the Spring Semester of 2008 when part of the paper was written.     

Incremental vapor sorption in a phase-segregated polyurethane elastomer

Incremental vapor sorption and desorption runs have been carried out with o-dichlorobenzene (ODCB) a strongly swelling solvent, in 2, 6, and 10 mil polyether polyurethane films. Two-stage sorption behavior occurs at intermediate and higher concentrations but is generally absent in the desorption runs. Analysis of the two-stage curves, using the Berens-Hopfenberg model of independent Fickian diffusion and first-order relaxation processes, leads to apparent diffusion coefficients which increase with thickness and show a pronounced maximum with concentration, whereas the relaxation rate constant decreases with concentration. Correction for the pressure drift during the runs, due to the low vapor pressure of ODCB, reduces the thickness dependence. The negative concentration dependence of the relaxation rate constant is related to the distribution of microdomain stabilities. Calculated values of the self-diffusion coefficient show that the maximum in the apparent diffusion constant with concentration can be accounted for largely, but not entirely, by the thermodynamic contributions. It is proposed that the additional factor is relaxation-controlled swelling which arises from the strong coupling between the matrix and hard-segment responses.     

Derivations, isomorphisms, and second cohomology of generalized Witt algebras

Generalized Witt algebras, over a field of characteristic , were defined by Kawamoto about 12 years ago. Using different notations from Kawamoto's, we give an essentially equivalent definition of generalized Witt algebras over , where the ingredients are an abelian group , a vector space over , and a map which is linear in the first variable and additive in the second one. In this paper, the derivations of any generalized Witt algebra
, with the right kernel of being , are explicitly described; the isomorphisms between any two simple generalized Witt algebras are completely determined; and the second cohomology group for any simple generalized Witt algebra is computed. The derivations, the automorphisms and the second cohomology groups of some special generalized Witt algebras have been studied by several other authors as indicated in the references.