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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Polymer bulletin 13 (1985), S. 293-299 
    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(β-malic acid) is a new synthetic functional polyester of the poly(β-hydroxy-acid)-type whose properties are investigated in regard to possible uses as bioresorbable polyvalent drug-carrier. Degradation of polymer chains in 0.15 N phosphate buffer at pH=7.5 is monitored by aqueous GPC on SEPHADEX gels and by enzymatic titration of ultimate degradation products. It is shown that the rate of degradation obeys first order kinetics at the begining and that poly(β-malic acid) degrades to malic acid at last.
    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 Acidic copolymers of the poly(β-hydroxy-acid) type containing β-malic acid (hydrophilic) and β-malic acid benzyl ester (hydrophobic) repeating units in various proportions are prepared by two differentes routes : — catalytic hydrogenolysis of the benzyl ester bonds of homopoly(β-malic acid benzyl ester) and — chemical coupling of benzyl alcohol to poly(β-malic acid). In attempts to account for the route-dependence of the physico-chemical properties of resulting copolymers, GPC in aqueous medium and measurements of the solubility of Yellow OB, a lipophilic dye, in aqueous solutions have been carried out. The results are discussed in regard to the sequence distributions of hydrophilic and hydrophobic repeating units.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-904X
    Keywords: mucoadhesion ; polyacrylic acid ; dextran ; copolymer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Water-soluble polymers were synthesized from dextran and polyacrylic acid and their ocular mucoadhesion was evaluated. One series had polyacrylic acid grafted onto the polysaccharide backbone of dextran, and another series had dextran grafted onto the polyacrylic acid backbone. Mucoadhesion of these copolymers was investigated using a tensile apparatus and compared with that of polyacrylic acid/dextran mixtures prepared in different proportions. Whatever the copolymer structure, no synergistic effects were seen and mucoadhesion was not markedly increased compared to dextran. The adhesion of copolymers was the same as that of mixtures having a similar polyacrylic acid content and was always less than that of polyacrylic acid alone. Formation of an interpolymer complex occurred at concentrations up to 60% polyacrylic acid, and only above this value did bioadhesion increase above that of dextran. When this complex was dissociated by neutralization of the carboxyl groups of polyacrylic acid, the mucoadhesion of the copolymers and the mixtures was improved. These experiments demonstrated that copolymers and mixtures of dextran and polyacrylic acid did not produce polymers with improved ocular mucoadhesion.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 583-593 
    ISSN: 0887-6266
    Keywords: enthalpy relaxation ; differential scanning calorimetry ; peak-shift method ; polymethyl(α-n-alkyl)acrylates ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In this work, we have investigated by DSC the structural relaxation of amorphous polymethyl(α-n-alkyl)acrylates in which it is possible to change the length of the alkyl chain. We have evaluated the Narayanaswamy parameter, x, which controls the relative contribution of temperature and of structure to the relaxation time, the apparent activation energy, Δh*, and the nonexponentiality parameter, β, of the stretched exponential response function. The results suggest that x increases while Δh* decreases and β remains constant as the length of the side chain increases. This allows us to comment on the effect of chemical modification on the relaxation kinetics. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 583-593, 1998
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 18 (1980), S. 1995-2000 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Improved methods for the synthesis of 4-halogeno 1-vinylnaphthalenes are proposed. Reactivity ratios are determined for the following systems: 4-fluoro-1-vinyl naphthalene-styrene, 4-chloro-1-vinyl naphthalene-styrene, and 4-bromo-1-vinyl naphthalene-styrene. The determinations are performed at various specific temperatures and the relative activation parameters are obtained. It appears that the reactivity of 1-vinyl naphthalene is drastically decreased when substituted by a halogen. In the case of 1-vinyl naphthalene the selection is enthalpically controlled.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 19 (1981), S. 891-896 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Transfer and termination constants have been determined for the cationic polymerization of 1- and 2-vinyl naphthalenes and 3-vinyl phenanthrene. They have been compared with the values obtained for styrene under the same experimental conditions. Experimental values are in good agreement with theoretical determinations.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The diffusional behaviour of chloramphenicolD-(-)-threo-N-[2-hydroxyl-1-hydroxymethyl-2-(4-nitrophenyl)ethyl]dichloroacetamide. (1) from poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogels is reported. The drug was trapped in the matrix cross-linked with various amounts of ethylene dimethacrylate (0,5-18 mol-%), and the diffusion was followed from disc-shaped slabs at swelling equilibrium in water (phosphate buffer, pH 7) at 37°C. The diffusion obeys the second Fick law and is rapid (D ≈ 10-8 cm2 s-1) in the case of the slightly crosslinked hydrogels used for corneal lenses. The diffusion coefficients decrease almost exponentially with increasing cross-linking ratio, and the process appears predominantly controlled by the free volume contribution of the diluent rather than by the sieving of the network.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Kinetics of hydrolytic release of chloramphenicol (1) chemically immobilized on HEMA-based ophthalmic hydrogels were examined. The rate constants of hydrolysis of the phenolic ester and acetal bonds of the spacer immobilizing the drug were determined at 37°C, and essentially at neutral pH, for the monomeric drug, the soluble copolymers and the cross-linked hydrogels, respectively. A drastic decrease in reactivity of the ester bond was observed from the small monomeric molecule to the soluble chains and then to the swollen network (relative reactivities ≈ 1300/25/1), whereas the acetal bond is less reactive, with a rate constant apparently independent of the size of the carrier. It is suggested that in all cases the ester bond is cleaved at first, liberating a drug bearing acetal intermediate which is then slowly hydrolysed to free chloramphenicol. All reactions were observed to be first order with respect to the hydrolysable precursor. When the rate constants are low enough, which is the case when considering the hydrogels, a pseudo-zero order is obtained and the release rate of chloramphenicol is constant over a long period of time and depends only on the initial concentration of immobilized, drug. Nevertheless, the too slow acetal hydrolysis in neutral physiological conditions limits the daily delivery to a few micrograms for a standard corneal lens with a 5 mol-% drug loading.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Three acrylate monomers having mesogenic moieties based on 4-(n)-alkyloxy-4′-(2-chloro-propanoyloxy)biphenyl (n = 6, 8 or 10) have been synthesized. There is no evidence for liquid-crystal properties in any of the three new monomers. The corresponding polymers have been prepared by free-radical polymerization. Their liquid-crystal behavior has been investigated by differential scanning calorimetry, polarized optical microscopy, and X-ray diffraction. On cooling from the isotropic liquid, smectic A (SA), smectic B (SB) and crystalline phases (probably crystal-like SE phases) have been evidenced. It should be noted that the chlorine atoms in the chiral groups do impose a local ordering of the mesogenic side groups.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Acrylate monomers with a chiral group have been synthesized bearing a propyl, isopropyl or benzyl substituent on the asymmetric carbon. All of the monomers are crystalline. Above their melting point, they give a clear, isotropic melt. The corresponding polymers have been prepared by free radical polymerization. They were examined by differential scanning calorimetry, optical microscopy and X-ray diffraction. They were found to show a reproducible liquid-crystal behavior. On cooling from the isotropic state, SA, SF* (or SI*) and crystal-like (probably SH or SH′) phases become evident. Our results do not preclude the existence of a SC* phase between the SA and SF* phases. It is noteworthy that polyacrylates of the same series but with side chains terminated by a chiral group bearing a methyl substituent exhibit SA, SB and crystal-like (probably SE) phases.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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