Search results for "Anhydride"
showing 10 items of 120 documents
Lineare polyester mit carboxylendgruppen und deren bestimmung
1955
Durch Umsetzung von „alkoholischen” Bernsteinsaure-1,6-Hexandiol-Polyestern mit Bernsteinsaureanhydrid in Benzol werden kettenanaloge Polyester mit endstandigen Carboxylgruppen hergestellt. Die Titration dieser Carboxylgruppen ergibt Molgewichte bis ∼ 7 · 103. Mit Phenylisocyanat in indifferenten Losungsmitteln reagieren Polyesterdicarbonsauren unter Kettenverlangerung und Bildung von kettenstandigen Carbonsaureanhydridgruppen. Die Umsetzung der Polyester-dicarbonsauren in Phenylisocyanat ohne Verdunnungsmittel erfolgt kettenanalog unter Bildung von Carboxanilidendgruppen. Durch photometrische Anilinbestimmung nach der Hydrolyse konnen diese Endgruppen quantitativ bestimmt und Molgewichte b…
Synthesis, characterisation and properties of α,β-poly(N-2-hydroxyethyl)-dl-aspartamide-graft-maleic anhydride precursors and their stimuli-responsiv…
2009
Abstract A family of poly(amino acid)-maleic anhydride hydrogels were designed and synthesized. Water soluble polymeric precursors were prepared by partially substituting the hydroxyl groups of the α,β-poly( N -2-hydroxyethyl)- dl -aspartamide backbone with maleic anhydride, so as to provide double bonds for crosslinking and carboxylic acid groups for pH and electric field responsiveness. Reaction conditions (reactive mixture composition and catalysis) were systematically varied in order to obtain PHEA–MA precursors with different and reliable graft-maleic anhydride levels. PHEA–MA precursors were characterised by titration, Nuclear Magnetic Resonance ( 1 H NMR), Fourier-Transformed Infrare…
Multilayer build-up of a reactive polymer with α,ω-functionalized chromophores
1997
Alternating multilayers with up to ten layers have been prepared by sequential reaction of a reactive polymer (poly[(1-methylvinyl isocyanate)-alt-(maleic anhydride)]) with α,ω-functionalized chromophores. For this purpose new chromophores were synthesized varying the length of the hydrophobic spacer. The analysis of the multilayer build-up shows that physisorption is more important than chemisorption for fixation of new polymer layers. Thus, a multilayer build-up is only possible with the shorter, more hydrophilic chromophore and not with the long hydrophobic spacer.
pH-sensitive hydrogel based on a novel photocross-linkable copolymer.
2004
A pH sensitive hydrogel has been prepared by a UV irradiation technique. Starting polymer was the PHM (poly hydroxyethylaspartamide methacrylated) obtained from polyaspartamide (PHEA) partially derivatized with methacrylic anhydride (MA). This new copolymer has been further derivatized with succinic anhydride (SA) to obtain PHM-SA that has been cross-linked by UV irradiation to form a pH sensitive hydrogel. The network, recovered after washing as a powder, has been been characterized by FT-IR spectrophotometry and particle size distribution analysis. Moreover, to have information about water affinity of the prepared sample, swelling measurements have been carried out in aqueous media mimick…
Recycling of the "light fraction" from municipal post-consumer plastics: Effect of adding wood fibers
1999
At present the recycling of plastic materials is mostly done using homogeneous polymers. Therefore a separation from a municipal collection of plastic objects is necessary before recycling operations. The easiest way of separation is by flotation in water, i.e. the separation of the different plastics based on the different densities with respect to water. This means that all the plastic materials are separated in a “light fraction” mostly of polypropylene and polyethylene and in a “heavy fraction” mainly of poly(vinyl chloride) (PVC) and poly(ethylene terephthalate). The recycling of the light fraction should, in principle, be easy because of the relative similarity of the chemical structu…
Study on compatibilization of polypropylene-liquid crystalline polymer blends
1997
The mechanical properties, melt rheology, and morphology of binary blends comprised of two polypropylene (PP) grades and two liquid crystalline polymers (LCP) have been studied. Compatibilization with polypropylene grafted with maleic anhydride (PP-g-MAH) has been attempted. A moderate increase in the tensile moduli and no enhancements in tensile strength have been revealed. Those findings have been attributed to the morphology of the blends, which is predominantly of the disperse mode. LCP fibers responsible for mechanical reinforcement were only exceptionally evidenced. Discussion of PP-LCP interfacial characteristics with respect to mechanical properties-morphology interrelations allowed…
Gamma radiation induced maleation of polypropylene using supercritical CO 2 : preliminary results
2000
Abstract The charging of maleic anhydride (MA) and dicumyl peroxide (DCP) into polypropylene matrices has been carried out by CO2 in supercritical conditions. The grafting of MA into polymer chains was done through gamma irradiation in CO2 atmosphere (0.1 MPa, 25°C). The grafting was successful and the amount of grafted anhydride was dependent on the amount of MA and DCP charged into the polypropylene matrix. The presence of grafted succinic anhydride was shown by FT-IR spectroscopy and its amount was determined through a calibration curve derived from standard samples. The effect of swelling due to supercritical CO2, maleic anhydride grafting and gamma irradiation on the molecular structur…
Enantioselective synthesis of sabina ketone
2003
Both enantiomers of sabina ketone were efficiently prepared via an easy synthesis of 1-diazo-5-methylene-6-methylheptan-2-one, starting from succinic anhydride, followed by its highly enantioselective cyclization catalyzed by chiral dirhodium(II) compounds having ortho-metalated phosphines as ligands.
ChemInform Abstract: Modified Photobehavior of Carboxylic Acid Derivatives Induced by Protonation.
1987
Abstract A series of carboxylic acid derivatives 1–6 containing a second interacting function have been converted into the corresponding O -protonated species or acylium ions upon treatment with 96% sulfuric acid or oleum, respectively, at room temperature. The resulting stable cations have been spectroscopically characterized and submitted to irradiation. Cis-trans photoisomerization was observed in the ionic speciesderived from trans -crotonic, fumaric and maleic acids, and maleic anhydride. By contrast protonated crotonolactone 5a+ was found to be photostable. Finally, protonated α-bromobutyrolactone 6a+ was clean and efficiently dehydrohalogenated to 5a+ upon irradiation. Since the norm…
Susceptibility of Methyl 3-Amino-1H-pyrazole-5-carboxylate to Acylation
2009
Abstract In the search for a new method of synthesis of hybrid peptides with aminopyrazole carboxylic acid, we tried to force selective acylation at the aromatic amino group instead of at the ring nitrogen atom with fairly gentle acylating agents. The acylating agents used were acid anhydrides: acetic anhydride, tert-butyl pyrocarbonate, and 2-(2-methoxyethoxy)ethoxyacetic acid/dicyclohexylcarbodiimide. We succceded in acylation at this amino group with almost none at the ring nitrogen atom. Sometimes, however, acylation in small quantities at the ring nitrogen atom was observed as a by-product. To remove this by-product, imidazole was used. Thus, we were able to obtain the hybrid peptides …