Polyanhydrides dehydrative coupling

We examined several approaches for synthesizing polyanhydrides, including melt polycondensation, dehydrochlorination, and dehydrative coupling. Extensive details of these new polymer synthesis techniques and numerous polymerization conditions for a wide variety of polyanhydrides were previously described (1). 

Leong, K. W., Simonte, V., and Danger, R., Synthesis of polyanhydrides Melt-polycondensation, dehydrochlorination, and dehydrative coupling. Macromolecules, 20. 705-712, 1987. 

The most widely used method to synthesize polyanhydrides is melt condensation polymerization, which results in high molecular weight polymers. Other methods include Schotten-Baumann condensation, dehydrative coupling, and ring opening polymerization. 

Another method to synthesize polyanhydrides is by dehydrative coupling of two carboxyl groups. Even though this method produces lower molecular weight products (mostly oligomers) compared with the methods described above, it is a single step polymerization where a dicarboxylie acid monomer can be directly converted into the polymer. Moreover, it can be conducted at low temperatures suitable for monomers that cannot resist harsh reaction conditions. 

Several approaches were examined for synthesizing polyanhydrides melt polycondensation, dehydrochlorination, and dehydrative coupling. A report of polyanhydride synthesis techniques and polymerization conditions for polyanhydrides appears in Leong et al. (22). 

Polyanhydrides have been synthesized by various techniques such as melt polycondensation, ring-opening polymerization, interfacial polycondensation, dehydrochlorination, and dehydrative coupling (13,14). The most widely used technique for polyanhydride synthesis is melt polycondensation, which occurs in two steps. In the first step, dicarboxylic acid monomers react with excess acetic anhydride to form acetyl-terminated anhydride prepolymers (1) with a degree of polymerization (DP) ranging from 1 to 20 (eq. 1). 

Polyanhydrides are biodegradable polymers with backbone composed of repeat units linked by anhydride bonds (Figure 16.15). They have been synthesized by several techniques, including melt-polycondensation, dehydrochlorination and dehydrative coupling. Melt-polycondensation is the method which allows the obtainment of POA with higher molecular weights [56]. 

The Synthesis of Polyanhydrides by Dehydrative Coupling. The synthesis of polyanhydrides was first reported in 1909 and led on to a series of aliphatic polyanhydrides being prepared in the 1930s, as potential materials for the textile industry. One method for the formation of such polyanhydrides, particularly where sensitive monomers are involved, is to find suit-... 

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