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  • 1
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Poly((3-hydroxypropyl β malate) has been synthesized starting from aspartic acid and benzyloxy-1-propanol as precursors. This new polymer was characterized by 1H and 13C NMR, size exclusion chromatography and differential scanning calorimetry. Homopolymer is soluble in water. Two kinds of amphiphilic copolymers were also prepared and characterized. Such polymers have been synthesized with a view to preparing non-charged degradable associating networks or drug carriers.
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  • 3
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The configurational analysis of racemic and optically active stereoisomers of 4-[(1′-methylpropyl)oxycarbonyl]-2-oxetanone has been carried out by using chiral gas chromatography. This technique has been successful in the stereoisomers composition determination of these β-substituted β-lactones prepared by two different routes and used as monomers in the preparation of malic acid stereocopolymers. Result are in good agreement with those obtained from high resolution 1H NMR, in the presence of an Europium salt, as chiral shift reagent. This method has been extended to 3-methyl-4-[(1′,2′,2′-trimethyl propyl)oxycarbonyl]-2-oxetanone. The exact knowledge of precursors configurational structure is very important in regard to the obtention of the corresponding polystereoisomers with a strictly controlled enantiomeric or diastereoisomeric composition and consequently with predictable properties.
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  • 4
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The anionic polymerization and copolymerization of butyl and benzyl malolactonates initiated with potassium acetate/dibenzo-18-crown-6 or [222] complex have been studied at 40°C in bulk and in dichloromethane and tetrahydrofuran solutions. Kinetics and polymer molecular weights were followed by SEC. In bulk and for conversion below 30%, molecular weights are close to those calculated for a living process then the conversion increase leads to a significant discrepancy between theoretical and measured molecular weights. In solution, side reactions take place significantly and no evident relationship between molecular weight and initiator concentration can be established, even at low conversion. Same situation was observed in the case of block copolymers synthesis. At last, evidence for transfer reactions has been shown by using model reactions.
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  • 5
    ISSN: 1572-8900
    Keywords: Macromonomers ; graft copolymers ; biocide release ; hydrolysis ; antifouling paints
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Environmental concerns result in a progressive withdrawal of antifouling paints containing organotin derivatives. The nature of the binders is critical with regard to the erosion of the protecting film through factors such as bond cleavage, dissolution, and diffusion of the degradation products. The versatility of acrylic polymers, due to the possibility of varying their chemical structure had conducted, in the first stage, to combine different types of repeating units in the macromolecular backbone. Formulation and evaluation, in natural sites, of these binders, with a well-defined hydrophobic/hydrophilic balance and with hydrolyzable pendant groups, have shown the possibility to prepare new organotin free resins which can be formulated and which are erodible in seawater over a long period (more than 2 years). A further step has been engaged with the development of graft copolymers containing biocompatible and hydrolyzable oligomers of α-hydroxyacids. Their preparation requires the synthesis of α-methacryloyloxyoligo-α-hydroxyacid macromonomers. Copolymers prepared from a mixture of the macromonomer and of an alkyl ester of acrylic acid were formulated with a biocide and deposited on a plate. Their ability to release cuprous oxide, as a model molecule, has been checked and quantified by the inductively coupled plasma analytical method. The uptake of water in the paint, which is enhanced by the hydrolysis of α-hydroxyacid oligomers, as determined by the enzymatic measurement of liberated L-lactic acid, conducts to the polymer erosion and to a protecting bioactive surface.
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  • 6
    ISSN: 1572-8900
    Keywords: Pseudomonas strains ; bacterial polyesters ; chemical modification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Sixteen Pseudomonas strains have been tested with a view to developing medium-chain length polyhydroxyalkanoates. Four strains were selected and it is shown that their ability for producing three different polyesters with variable properties was dependent on the strains and substrates. Otherwise, Pseudomonas oleovorans was grown on a mixture of sodium octanoate and undecenoate salts at a 90/10 mol/mol ratio. The corresponding copolymer, bearing lateral double bonds, was chemically modified in the carboxy group. Finally, the ability to tailor-make functional bacterial polyesters aimed at temporary therapeutic applications is demonstrated.
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  • 7
    ISSN: 1572-8900
    Keywords: Hydrolysis ; erosion ; acrylic acid polymers ; antifouling ; GC-MS ; coulometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Specific polymeric material applications as bioactive molecules delivery systems involve a strictly controlled degradation of polymer matrixes. One possibility to obtain a zero-order kinetic for small molecules release consists in a simple hydrolysis of ester groups contained in the macromolecular structure. The chemical degradation can lead to the continuous surface erosion of the formulated resins without loss of their mechanical properties and to a permanent activity of the delivery systems. Hydrolysis is a very well-known reaction in the case of organic molecules containing ester groups. The mechanism seems to be more complicated when ester groups are located in macromolecular structures. With the aim of antifouling applications, acrylic acid polymers bearing lateral ester groups of different chemical structures (hydrophilic, hydrophobic, hydrolyzable) have been prepared, characterized, and immersed in water, at pH 8, and their hydrolysis has been studied. Experimental data display two parameters, at least, which must be taken into account: the reactivity of the ester groups toward hydrolysis and the hydrophilic/hydrophobic balance of the polymer. The susceptibility of the acrylic polymers to hydrolysis has been compared to the erosion characteristics of the corresponding films. The results confirm that hydrolysis is necessary to obtain a regular degradation of the films without loss of mechanical properties. A relationship has been observed between the characteristics of hydrolysis and erosion for each studied polymer.
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  • 8
    ISSN: 1572-8900
    Keywords: Biocompatible polyesters ; Clostridium tetanomorphum ; optically active ; degradable polymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Design of optically active polymeric materials for temporary therapeutic and environmental applications requires the working-out of functionalized polymers with structures and properties adjusted to the considered applications. Biocompatibility of selected polymers is a required property in regard to the interactions between living organisms and macromolecular systems. It is therefore important to prepare highly optically active monomers and their corresponding hydrolyzable and biocompatible polymers. Bacterium Clostridium tetanomorphum is an useful source of enzymes for bioconversion and particularly in the chemoenzyrnatic route to optically active alkylmalolactonic acid esters and their optically pure stereoisomers. 3-Methylaspartase, involved in the glutamate fermentation pathway, is a very interesting enzyme, which can provide chiral precursors with high optically purity. This chemoenzymatic strategy can be used to prepare the four stereoisomers of 3-methylmalolaconic acid esters, by enzymatic resolution of natural and artificial stereoisomers of 3-methylaspartic acid. A series of 3-alkymalolactonic acid esters with alkyl equal to ethyl or isopropyl, have been also synthesized and transformed into corresponding optically active polyesters.
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  • 9
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Racemic and optically active 4-carboxy-2-oxetanones have been prepared, starting from racemic, (R)-4-benzyloxycarbonyl-2-oxetanone, by catalytic hydrogenolysis of the lateral benzyl protecting group. This new β-substituted-β-lactone (malolactonic acid), which was considered as totally unstable due to the presence of a carboxyl group, has been isolated, characterized and prepared in large quantities. The liberated carboxylic acid function can be used for coupling reactions with different types of molecules in the goal to tailor make functionalized multimeric macromolecules (reactive polymers, supported catalysts, liquid crystals polymers, macromolecular prodrugs). This possibility has been examplified by using 2, 4, 5-trichlorophenol as activating agent and chloramphenicol as bioactive molecule, which have been bound to malolactonic acid and then copolymerized by anionic ring opening polymerization in the presence of 4-benzyloxycarbonyl-2-oxetanone. It has been shown that this new route conducts to activated derivatives of poly (malic acid) and polymeric drug carriers patterns.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Polymer bulletin 14 (1985), S. 187-192 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary A simple and reproducible method of synthesizing enantiomers of benzyl malolactonate is described starting from optically active aspartic acid. Chiral benzyl malolactonate is a β-substituted β-lactone monomer which can be readily polymerized anionically using triethylamine as the initiator to yield poly(benzyl β-malate) which is an optically active, semicrystalline polymer. Cleavage of protecting benzyl ester groups yields optically active poly(β-malic acid). The properties of the racemic and optically active monomers and polymers are compared. Optically active (−)poly(β-malic acid) shows one accessible positive CD band in the far UV.
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