Substituted Side Groups Research Articles

Applications of Polyacetylene Derivatives in Gas and Liquid Separation

As a low energy consumption, simple operation and environmentally friendly separation method, membrane separation has attracted extensive attention. Therefore, researchers have designed and synthesized various types of separation membrane, such as metal organic framework (MOF), covalent organic framework (COF), polymer of intrinsic micro-porosity (PIM) and mixed matrix membranes. Some substituted polyacetylenes have distorted structures and formed micropores due to the existence of rigid main chains and substituted side groups, which can be applied to the field of membrane separation. This article mainly introduces the development and application of substituted polyacetylenes in gas separation and liquid separation based on membrane technology.

Multifunctional Properties of Glycoside Hydrolase Family 43 from Paenibacillus curdlanolyticus Strain B-6 Including Exo-β-xylosidase, Endo-xylanase, and α-L-Arabinofuranosidase Activities

The glycoside hydrolase family 43 from Paenibacillus curdlanolyticus strain B-6 (GH43B6) exhibited multifunctional properties, including exo-β-xylosidase, endo-xylanase, and α-L-arabinofuranosidase enzymatic activities. GH43B6 released xylose as a hydrolysis product from the successive reduction of xylooligosaccharides as a result of exo-β-xylosidase activity. Moreover, GH43B6 also predominantly released xylose from low-substituted xylan derived from birchwood. However, when the highly substituted rye flour arabinoxylan was used as a substrate, exo-β-xylosidase activity changed to endo-xylanase activity, indicating that the enzymatic property of GH43B6 is influenced by the substituted side groups of xylan. For α-L-arabinofuranosidase, arabinose was released from short-chain substrates including p-nitrophenyl-α-L-arabinofuranoside and α-L-Araf-(1→2)-[α-L-Araf-(1→3)]-β-D-Xylp. This study reports the novel trifunctional properties of GH43B6 containing exo- and endo-activity together with xylanolytic debranching enzymatic activity, which increases its potential for application in lignocellulose-based biorefineries.

Molecular mobility of substituted poly(p-phenylenes) characterized by a range of polymer relaxation techniques

The free volume and related mobility properties of substituted poly(p-phe-nylene) polymers are examined. The techniques used range from positron annihilation, dielectric relaxation, and dynamic mechanical spectroscopy to thermally stimulated currents. Fractional free volume is determined for the samples with different substituted side groups and related to the glass transition temperature. Bulkier groups lead to a greater fractional free volume and lower glass transition temperatures. Comparison of molecular relaxation times using the different characterization techniques demonstrates that there is strong coupling between motion of the main chain and the side groups, on which the dipoles reside. Intermolecular coupling between the main chains at the primary relaxation is shown in this work to be related to the nature of the side chains and resultant free volume, as are the temperature locations of local, secondary relaxations. A qualitative model describing the effect of regiochemistry on the motions and packing of these materials is also proposed.

Molecular mobility of substituted poly(p‐phenylenes) characterized by a range of polymer relaxation techniques

The free volume and related mobility properties of substituted poly(p-phenylene) polymers are examined. The techniques used range from positron annihilation, dielectric relaxation, and dynamic mechanical spectroscopy to thermally stimulated currents. Fractional free volume is determined for the samples with different substituted side groups and related to the glass transition temperature. Bulkier groups lead to a greater fractional free volume and lower glass transition temperatures. Comparison of molecular relaxation times using the different characterization techniques demonstrates that there is strong coupling between motion of the main chain and the side groups, on which the dipoles reside. Intermolecular coupling between the main chains at the primary relaxation is shown in this work to be related to the nature of the side chains and resultant free volume, as are the temperature locations of local, secondary relaxations. A qualitative model describing the effect of regiochemistry on the motions and packing of these materials is also proposed. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1465–1481, 1998

Third Order Nonlinear Optical Properties of Novel Polythiophene Derivatives

The third order nonlinear optical properties of polythiophene derivatives produced by a novel application of Stille coupling were investigated by degenerate four wave mixing (DFWM) and third harmonic generation (THG). By systematic changes in the substituted side groups, values of the third order susceptibility, χ(3), reached 1.8×10−9 esu (by DFWM) with a figure of merit χ(3)/α ∼ 7±10−14esu·cm.

A comparison of polarographic reduction potentials of some substituted benzoquinolizinium compounds

AbstractThe presence of substituted side groups on the benzoquinolizinium ion has a measurable effect on the magnitudes of the reduction potentials. Qualitative relationships between inductive and/or resonance effects of these side groups and the corresponding half‐wave potentials are discussed.