To elucidate the effect of tin compounds in the ring-opening polymerization of lactides and lactones, D,L-dilactide was taken as an example, and its reaction with different tin compounds at a molar ratio of 1: 1 as well as the polymer formation and degradation in dependence of its concentration has been investigated. Two entirely different reaction courses were observed which are consequently influenced by compounds with alcoholic and/or carboxylic OH groups in different ways.
Biologisch abbaubare Polymere. 7. Mitt.: Z u m Mechanismus der Ringoffnungspolymerisation cyclischer Ester von aliphatischen Hydroxy-carbonsauren mit verschiedenen ZinnverbindungenUm den Einflulj von Zinnverbindungen bei der Ringoffnungspolymerisation von Lactiden und Lactonen aufzuklaren, wurde D,L-Dilactid als Beispiel eingesetzt. Die Reaktion mit verschiedenen Zinnverbindungen beim Molverhaltnis 1: 1 sowie die Polymerbildung und der Polymerabbau in Abhangigkeit von der Konzentration wurden untersucht. Es wurden zwei verschiedene Reaktionswege gefunden, die durch Verbindungen mit alkoholischen und/oder carboxylischen OH-Gruppen unterschiedlich beeinfluljt werden.
The ring‐opening polymerization of D, L‐dilactide and an equimolar dilactide‐diglycolide mixture has been investigated. Conversion and molecular weight in the lactide bulk polymerization are determined not only by the kinetics of the primary ring‐opening reaction, but also by the concentration and extent of consecutive reactions of reactive groups in the polyester formed. High conversions and high molecular weights are obtained only by high polymerization rates. For the characterization of the polymers, viscosity‐molecular weight relationships for monomer‐containing ‘equilibrium’ polymers and reprecipitated polymers were determined. The application of these polymers in parenteral drug delivery systems for a gonadotropin‐releasing hormone agonist has been investigated.
Several kinds of commercially available polymers of the type poly(oxy‐1,4‐phenylenecarbonyl‐1,4‐phenylene) were sulfonated by reaction with mixtures of sulfuric acid and oleum. The ether/carbonyl group ratio of the polymer chain varied from 0.67 to 2.0. With decreasing amounts of ether links in the polymer backbone the sulfonation is hindered and the reaction conditions have to be stronger. To yield the same degree of sulfonation, the sulfuric trioxide concentration of the reaction mixture has to be increased. The achievable degree of substitution is limited, in general, to one sulfonate group per substitutable unit (oxy‐phenylene‐oxy‐ or oxy‐phenylene‐carbonyl unit). In dependence on the polymer structure, polymers with contents of sulfonate groups between 1.2 and 2.0 meq·g–1 polymer are well soluble in dimethylformamide or N‐methylpyrrolidone and it is possible to produce membranes with permselectivities >96% and electrical resistances < 2 Ω cm–2. The sulfonated polymers were characterized by viscosimetry, sedimentation analysis and 13C NMR spectroscopy.
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