Hydroxyl Benzoic Acid Research Articles

Strengthening of liquid crystalline polymer by functionalized carbon nanotubes through interfacial interaction and homogeneous dispersion

Multiwalled carbon nanotubes (MWCNTs) were functionalized with two types of chemical moieties (i.e. carboxylic, COOH and hydroxyl benzoic acid groups, ‐HBA) on their sidewalls in order to improve their interaction with a liquid crystalline polymer (LCP) and dispersion in LCP. We have investigated the rheological, mechanical, dynamic mechanical, and thermal properties in detail with variation of HBA‐functionalized MWCNTs in the LCP matrix. Effect of the dispersion state of the functionalized MWCNTs in the LCP matrix on the rheological behavior was also studied. The composites containing HBA‐functionalized MWCNTs showed higher complex viscosity, storage, and loss modulus than the composites with the same loading of raw MWCNTs and MWCNT‐COOH. It was suggested that the HBA‐functionalized MWCNTs exhibited a better dispersion in the polymer matrix and formed stronger CNT‐polymer interaction in the composites than the raw MWCNTs and MWCNT‐COOH, which was also confirmed by FESEM and FTIR studies. As a result, the overall mechanical performance of the HBA‐MWCNT‐LCP composites could be improved significantly. For example, the addition of 4 wt% HBA‐MWCNT to LCP resulted in the considerable improvements in the tensile strength and modulus of LCP (by 66 and 90%, respectively). Copyright © 2010 John Wiley & Sons, Ltd.

Linear and networked polymers formed by the near simultaneous occurrence of etherification and esterification under mild reaction conditions

Despite the large difference in their nucleophilicity, phenoxide and carboxylate anions take part nearly simultaneously in the aliphatic nucleophilic substitution reaction with 1,4-dibromo-2-butene. This leads to the formation of ether (O) and ester (COO) linkages simultaneously under mild reaction conditions when hydroxyl benzoic acids are employed as nucleophiles. The process yields a new class of polymer broadly classified as unsaturated poly(ether ester) which are potentially functionalizable. This methodology has also been extended for preparing networked polymers by making use of 3,5-dihydroxybenzoic acid as A3 type monomer. Copyright © 2011 Society of Chemical Industry

Specific Functionalization of Carbon Nanotubes for Advanced Polymer Nanocomposites

AbstractA novel approach to chemically functionalize multiwalled carbon nanotubes (MWCNTs) for making advanced polymeric nanocomposites with liquid crystalline polymers (LCPs) is presented. In this approach, two types of chemical moieties (i.e., carboxylic and hydroxyl benzoic acid groups) are selectively introduced onto the sidewalls of the MWCNTs. Fourier transform IR and Raman spectroscopy are used to examine the interaction between the functionalized MWCNTs and the LCP. The strong interaction between the functionalized MWCNTs and the LCP greatly improved the dispersion of MWCNTs in the polymer matrix as well as the interfacial adhesion. The dispersion of the MWCNTs in the LCP matrix is observed by optical microscopy and field‐emission scanning electron microscopy. As a result, the addition of 1 wt% MWCNTs in the LCP resulted in the significant improvement (41 and 55%) in the tensile strength and modulus of the LCP.

Phytochemical and biological investigation of chloroform and ethylacetate fractions of Euphorbia heterophylla leaf (Euphorbiaceae)

Euphorbia heterophylla Linn (Euphorbiaceae) is a medicinal plant used by traditional herbal practitioners in Nigeria and some parts of West Africa for the treatment of constipation, bacterial and inflammatory disease conditions (arthritis and rheumatism). Powdered plant material was subjected to phytochemical screening using standard experimental procedures. The crude powdered sample of Euphorbia heterophylla leaves was extracted with n-hexane, chloroform, ethylacetate and methanol. The precipitates from the fractions were subjected to chromatographic and re-crystallization procedures. The structures of isolated compounds were characterized and elucidated with chemical and spectroscopic techniques such as IR, NMR and MS experiments. The in vitro biological activity of the isolated and characterized compounds were evaluated by superoxide scavenging assay using xanthine – xanthine oxidase system to generate superoxides. The result of the study showed that the crude plant material contained some secondary metabolites such as saponins, flavonoids and tannins. The phytochemical investigation led to the isolation of four known compounds stigmasterol, β-stigmasterol glucoside, benzoic acid and 4 – hydroxyl benzoic acid. The four compounds exhibited good activity against the xanthine oxidase enzymes while the 4-hydroxybenzoic acid showed a marked activity. The isolation of the compounds from the leaves of E. heterophylla, which inhibited the xanthine oxidase enzyme, has justified the claims for which the plant is known and used. Key words: Euphorbia heterophylla, euphorbiaceae, xanthine oxidase activity, superoxide scavenging, steriods.

Studies about Thermal Decarboxylation of Hydroxyl Benzoic Acids used in Thermal Imaging.

Six isomers of dihydroxyl benzoic acid and three isomers of trihydroxyl benzoic acid were analysed systematically with thermogravimetric analysis. They, the starting temperatures (TS), the peak temperatures (TP) and the end temperatures (Te) in the decarboxylation reactions, were worked out based on the integral curves (TG) and the differential curves (DTG) in thermogravimetric analysis of these compounds. The carbon atoms of benzene rings connected with carboxyl groups of these compounds are numbered as C1, and the carbon atoms of carboxyl groups are numbered as C7. The chemical shift values of C1 (δ1) and C7 (δ7) are from the NMR spectra of these compounds, and it is found that there is a linear relation between TP and δ1 or (δ7-δ1). The net charge values of C1 (q1) and C7 (q7) are from the calculations of quantum chemistry. After compared δ1 and(δ7-δ1) with q1 and(q7-q1) respectively, it is also found that there are linear relations between them. These prove that there is a close relation among δi, qi and the reactivity of i-position on the benzene ring of a phenolic compound.

Synthesis, luminescence properties and energy transfer of binary and ternary rare earth complexes with aromatic acids and 1,10‐phenanthroline

AbstractA series of binary and ternary ram earth (Gd, Eu, Tb) complexes with ortho hydroxyl benzoic acid, para aminobenzoic acid, nicotinic acid and 1,10‐phenanthroline were synthesized. Phosphorescence spectra and lifetimes of Gd complexes were measured and the lowest triplet state energies of gadolinium binary complexes and the intramolecular energy transfer efficiencies were determined. The luminescence properties and energy transfer process of Eu3+and Tb3+ complexes were discussed.