Synthesis of polyanhydrides. X.1 Mixed anhydrides of aromatic and five‐membered heterocyclic dibasic acids2

Copolycondensation reactions of mixed anhydrides of five‐membered heterocyclic dibasic acids and terephthalic acid investigated. As monomers of five‐membered heterocyclic dibasic acids, furan‐2,5‐di‐β‐propionic acid, tetrahydrofuran‐2,5‐di‐β‐propionic acid, thiophene‐2,5‐di‐β‐propionic acid, N‐methylpyrrole‐2,5‐di‐β‐propionic acid and N‐methylpyrrolidine‐2,5‐di‐β‐propionic acid have been prepared in high yields from readily available furfural and levulinic acid as a starting materials. Copolycondensation reactions of terephthalic acid and various heterocyclic dibasic acids were carried out by treatment with acetic anhydride. The mixed polyanhydrides of random structure were synthesized and the plot of composition versus melting point was obtained. The mole fractions of the two acid components were found to be 40–60 mole‐% of terephthalic acid and 60–40 mole‐% of five‐membered heterocyclic dibasic acid for copolymers melting at 200–300°C. It was confirmed from the relationship between copolymer composition and crystalline melting temperature of a random copolymer that the following FLORY's equation holds for the mixed polyanhydrides. magnified image From FLORY's equation, the value of heat of fusion per repeating unit of crystallite, hu = 1,600–3,300 cal./repeating unit, and entropy of fusion, Su = 3.8–8.0 cal./repeating unit/deg. were obtained. Moreover, mixed polyanhydrides of three components such as terephthalic acid and two kinds of heterocyclic dibasic acids have been prepared. The molecular structure of new heterocyclic mixed anhydrides was presumed on the basis of infra‐red spectra, degree of polymerization and X‐ray diagrams of these polymers.