Organosoluble polyimides for second-order nonlinear optics

[[abstract]]A new class of crosslinked polymer network based on organosoluble polyimides for second-order nonlinear optics (NLO) has been developed. The Tg's of these aromatic polyimides can be tailored to suit subsequent processing and reaction. An NLO-active alkoxysilane dye, serving as the crosslinking agent, introduces a crosslinking reaction between polyimide chains forming a polymer network. Second harmonic coefficients, d33 were found to be 15 to 20 pm/V at 1.06 μm in the poled samples. Excellent long-term stability of the effective second harmonic coefficients (deff) at 120 °C is also observed.[[fileno]]2010123010052[[department]]物理

Swollen polymeric complex membranes for olefin/paraffin separation

Swollen complex membrane of linear low density polyethylene-graft-poly(acrylic acid)-Ag+ (LLDPE-g-AA-Ag+) were studied and compared with the corresponding membranes based on silicone rubber (SR) and poly[1-(trimethylsilyl)-1- propyne] (PTMSP), such as SR-g-AA-Ag+ and PTMSP-g-AA-Ag+. The polymeric matrix was first grafted with acrylic acid (AA) and then incorporated with silver ions (Ag+) in glycerol solution for forming the swollen complex membrane. Various metal ions and swollen agents in membranes for isobutene/isobutane separation were presented, The swelling of the complex membrane containing Ag+ with glycerol shows a higher olefin/paraffin selectivity than those membranes containing Cu+ or Cu2+ ions and/or other swelling agents. The gas permeability coefficients and the isobutene/isobutane selectivity of LLDPE-g-AA-Ag+ membrane were compared with those of SR-g-AA-Ag+ and PTMSP-g-AA-Ag+ membranes. The PTMSP-g-AA-Ag+ complex membrane was found to reach high gas permeability and high olefin/paraffin selectivity. The effects of solubility and diffusivity in membranes are compared with the corresponding non-Ag membranes. The sorption properties in these complex membranes were also included. (C) 1998 Published by Elsevier Science B.V

Heterobifunctional membranes by plasma induced graft polymerization as an artificial organ for penetration keratoprosthesis

Highly biocompatible polymer membrane was developed for an artificial cornea in this surface modification study. Heterobifunctional silicone rubber membranes (hetero-SR) were prepared by grafting different functional polymers on each side of a silicone rubber membrane (SR). A novel type of bifunctional membrane was developed with the upper-side favoring cell attachment and growth, and the lower-side suppressing cell adhesion. The preparation of heterobifunctional membranes, characterization of polymer membrane surface properties such as ATR-FTIR and ESCA and contact angle, and biological analysis (in vitro and in vivo studies) were investigated in this work. Based on the biological analysis, the heterobifunctional membrane displays promising potential for use as an artificial cornea. (C) 1998 John Wiley gr Sons, Inc

Synthesis, thermal and dielectric properties of a photocrosslinkable ferroelectric liquid crystal and its copolymers

A series of new ferroelectric liquid crystal a (FLC) copolymers based on a photocrosslinkable ferroelectric liquid crystal was synthesized. Chemical structures were analyzed by H-1 NMR and FT-TR spectroscopy. Liquid crystal phases of these photocrosslinkable materials were characterized by differential scanning calorimetry, optical polarizing microscopy, and X-ray diffraction measurements. A wide temperature range of chiral smectic (S-C*) phase (approximately 100 degreesC) was found for the a monomer and its copolymers. Microscopic phase separation was observed when the graft ratios of the FLC monomer were 15%, 35%, and 55%. Dielectric relaxation behavior of the ferroelectric Liquid crystal copolymers was investigated by broadband dielectric relaxation spectroscopy. As the graft content of liquid crystal decreased, the relaxation intensity and frequency of the S-C* phase increased, The relationship between thermal dynamics and chemical structure was also discussed

Novel guest-host NLO poly(ether imide) based on a two-dimensional carbazole chromophore with sulfonyl accepters

Taking advantage of the multifunctional characteristics of carbazole along with rational molecular design, a two-dimensional (2-D) carbazole chromophore was synthesized by a facile synthetic route. By doping of the chromophores into an organosoluble poly(ether imide), a series of guest-host NLO polymers were acquired. A high doping level up to 38 wt % was obtained without observing aggregation of NLO chromophores. The second harmonic coefficients (d(33)) for the guest-host system range from 5 to 22 pm/V, dependent on the doping level. The compatibility between chromophore and poly(ether imide) was investigated by SEM and extraction experiment. In the aspect of compatibility, the molecular weight distribution of the polymer plays an important role. The effect of two-dimensional structure on the NLO temporal stability was investigated by tracing the second harmonic coefficient as functions of temperature and time, respectively. Moreover, the relaxation behavior of the NLO systems was further examined by dielectric analysis. Large rotational cone volumes give the two-dimensional chromophore excellent orientational stability when the temperature approaches the glass transition temperature observed from DEA

3D-QSAR studies on PU3 analogues by comparative molecular field analysis

A comparative molecular field analysis (CoMFA) of PU3 derivatives of Hsp90 (Heat shock protein 90) inhibitors has been performed to determine the factors contributing the corresponding activities. The energy minimized conformations were obtained by molecular mechanics using SYBYL package. The developed model, with r(2) value of 0.947, was verified by performing leave-one out (LOO) cross-validation, which showed q(2) value of 0.513. The calculated model not only elucidates the relationship between compound structures and biological activities but, more importantly, facilitates design of new Hsp90 inhibitors with calculated antiproliferative activity. (C) 2003 Elsevier Ltd. All rights reserved

Synthesis and characterization of pH-sensitive dextran hydrogels as a potential colon-specific drug delivery system

pH-Sensitive dextran hydrogels were prepared by activation of dextran (T-70) with 4-nitrophenyl chloroformate, followed by conjugation of the activated dextran with 4-aminobutyric acid and cross-linking with 1,10-diaminodecane. The cross-linking efficiencies determined by mechanical measurements were in the range of 52-63%. Incorporation of carboxylpropyl groups in dextran hydrogels led to a higher equilibrium and faster swelling under high pH conditions. The swelling reversibility of hydrogels was also observed after repeated changes in buffers between pH 2.0 and 7.4. The slow rates of swelling and deswelling in response to changes in pH were attributed to the hydrophilic nature of dextran and formation of hydrogen bonds between the hydroxyl groups of dextran with water molecules. The pronounced effect of carboxylic acid content on degradation of hydrogels was observed after 4 h of incubation with dextranase and the influence significantly decreased after exposure to the enzyme for 8 h. The mechanism of bulk degradation of hydrogels under high swelling extent was substantiated using Coomassie blue protein assay. The release rate of bovine serum albumin from hydrogrels was primarily determined by the swelling extent. The release rate was further enhanced by addition of dextranase in buffer solutions

Organic/inorganic NLO materials based on reactive polyimides and a bulky alkoxysilane dye via sol/gel process

A series of the organic-inorganic materials based on reactive polyimides and a bulky alkoxysilane dye (ASD) for second-order nonlinear optics have been developed. Sol-gel reaction of ASDs is utilized to grow a network in polymer matrices (composite) or to create inter-polymer network among polyimide chains (hybrid). Moreover, a full interpenetrating polymer network (IPN) was formed through simultaneous free radical polymerization of a methacryloyl group containing polyimide, and sol-gel process of ASDs. Scanning electron microscopy (SEM) results indicate that the inorganic networks are distributed uniformly throughout the polymer matrices on the molecular scale. The silica particle sizes are well under I gm based on AFM study. Second harmonic coefficients, d(33) of 4.5 to 48.5 pm/V have been obtained for the optically clear poled/cured polyimide/ASD samples. Excellent temporal stability was obtained for these NLO materials at 100degreesC. The dynamic thermal and temporal stabilities of the IPN system were much better than those of composite and hybrid systems. Copyright (C) 2003 John Wiley Sons, Ltd