Ferroelectric nanofibers with an embedded optically nonlinear benzothiazole derivative

We report measurements of the molecular first hyperpolarizability, thermal stability, photophysical, piezoelectric and ferroelectric properties of a benzothiazole derivative bearing an arylthiophene π-conjugated bridge both in solution and when embedded into a poly (L-lactic acid) (PLLA) matrix in the form of electrospun fibers with an average diameter of roughly 500 nm. The embedded nanocrystalline phenylthienyl-benzothiazole derivative, with crystal sizes of about 1.4 nm resulted in a good piezoelectric response from these functionalized electrospun fibers, indicative of a polar crystalline structure.Fundação para a Ciência e a Tecnologia (FCT

Synthesis and characterization of thermally stable second-order nonlinear optical side-chain polyimides containing thiazole and benzothiazole push-pull chromophores

Push-pull nonlinear optical (NLO) chromophores containing thiazole and benzothiazole acceptors were synthesized and characterized. Using these chromophores a series of second-order NLO polyimides were Successfully prepared from 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), pyromellitic dianhydride (PMDA) and 3,3'4,4'-benzophenone tetracarboxylic dianhydride (BTDA) by a standard condensation polymerization technique. These polyimides exhibit high glass transition temperatures ranging from 160 to 188 degrees C. UV-vis spectrum of polyimide exhibited a slight blue shift and decreases in absorption due to birefringence. From the order parameters, it was found that chromophores were aligned effectively. Using in situ poling and temperature ramping technique, the optical temperatures for corona poling were obtained. It was found that the optimal temperatures of polyimides approach their glass transition temperatures. These polyimides demonstrate relatively large d(33) values range between 35.15 and 45.20 pm/V at 532 nm. (C) 2008 Elsevier B.V. All rights reserved

Influence of clay content and amount of organic modifiers on morphology and pervaporation performance of EVA/clay nanocomposites

Poly(ethylene-co-vinyl acetate)/organically modified clay nanocomposites were prepared using different clay loadings and by varying the amount of organic modifier. The morphology of the nanocomposites was investigated using small-angle X-ray scattering (SAXS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). SAXS results displayed intercalation of polymeric chains between the silicate layers in all the cases. The interlayer distance varies slightly between the series. TEM images showed a better dispersion of the clay platelets at lower loading for both series of samples. The pervaporation performances of membranes were analyzed using a chloroform/acetone mixture. Membranes displayed high selectivity. The influence of feed composition on pervaporation was analyzed. The nanoclay content and the influence of free volume on pervaporation performance were also investigated in detail. A drop in selectivity and an increase in permeation rate were observed at higher clay loadings

Study of styrene effect on non-radiation grafting of vinyl benzyl chloride on to polyethylene-based anion exchange membrane

A non-radiation polyethylene-based anion exchange membrane (AEM) was synthesized by chemically grafting 4-vinylbenzyl chloride (VBC) onto it. The resulting AME with a 10% styrene addition has peak IEC value, 57% higher than the non-styrene AEM. Water uptake and mechanical properties were slightly enhanced with the presence of styrene. The addition of styrene improves the compatibility between VBC and low-density polyethylene due to the formation of compatibilizer of poly(styrene-co-VBC). These were evidenced by elemental analysis, infrared spectroscopy, [1] H NMR, and Field Emission-SEM