| SYNTHESIS |
Methods for solution polymerization of polyanhydrides are reported by Leong et al. in Macromolecules 20(4), 705-712 and Shopor et al. Chem. Abst. 76, 91956w (1969). The following method is described by Domb, et al. in co-pending application entitled "One Step Polymerization of Polyanhydrides" filed on July 30, 1987. One equivalent coupling agent was added dropwise to a stirring solution of 1 eq. dicarboxylic acids and 2.5 eq. base in chloroform. The reaction mixture was stirred at 25.degree. C. for 3 hours. When either poly(4-vinylpyridine) (PVP) or K.sub.2 CO.sub.3 was used as the acid acceptor, the insoluble solids (e.g., PVP.HCL, KCl) were removed by filtration. The filtrate was quenched in excess petroleum ether. The precipitated polymer was isolated by filtration and dried in a vacuum oven at 40.degree. C. for 24 hours. When either triethylamine (TEA) or pyridine were used, the polymerization mixture was quenched in petroleum ether. The precipitated polymer was redissolved in chloroform and washed rapidly with cold water, pH 6.0. The chloroform solution was dried over MgSO.sub.4, and quenched a second time in petroleum ether. Insoluble polyanhydrides, pFA or poly(fumaric-sebacic) anhydride (p(FA:SA))(93:7), were polymerized as above, but with only soluble amines (TEA or pyridine), as the acid acceptors. The polymer precipitated during the polymerization and was isolated by filtration. Polymerization of fumaric acid and its copolymers with sebacic acid shows similar results whether polymerization is with a coupling agent such as phosgene or diphosgene or an acid-acid chloride polymerization reaction. For either reaction, soluble or insoluble bases are suitable as acid acceptors. |
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