Synthesis of poly(glycolic acid) in ionic liquids

Abstract

The synthesis of poly(glycolic acid) (PGA) by polyesterification of glycolic acid was studied using ionic liquids, mainly 1,3-dialkylimidazolium salts, as reaction media. The 1 H NMR spectra of PGA oligomers were assigned and end-group signals were used to follow the reaction. Low PGA yields were obtained by the direct polyesterification of glycolic acid at 200-240 8C, because of monomer evaporation during the reaction. On the other hand, PGAs of DP n up to 45 were obtained by the postpolycondensation of a preformed oligomer in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (BMIm þ Tf 2 N À ). The precipitation of PGA in reaction medium at long reaction times limited the achievable molar mass. Rate constants were determined for catalyzed and noncatalyzed reactions, assuming a second-order reaction mechanism. The efficiency of esterification catalysts such as Zn(OAc) 2 was low in these media, as only about twofold increases in reaction rate were observed. This was assigned to the preferential interaction of Zn 2þ with ionic liquid anion instead of the polymer carboxylic acid end-groups. V V C 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: [3025][3026][3027][3028][3029][3030][3031][3032][3033][3034][3035] 2006

High temperature reaction between poly(glycolic acid) and ε-caprolactone in ionic liquids

“…The degree of randomness of all copolyesters was close to 1 and DP n close to 30 ( Table 2). As previously reported for PGA homopolymer polyesterification carried out in ionic liquids [36], the nature of catalyst does not much influence the reaction.…”

“…Unlike PGA homopolyester [36], the copolyesters remained soluble in the ionic liquid reaction medium at the copolymerization temperature. 3).…”

“…The downfield resonance at 4.82 ppm (H a ) was assigned to GGG triads by comparing with the spectrum of PGA [36]. The series of more shielded peaks (H b,c,d ) are due to LGG, GGL and LGL triads.…”

“…In a previous work, we reported on the polycondensation of glycolic acid (GA) and on the post-polycondensation of PGA oligomers in ionic liquids, mainly in 1,3-dialkylimidazolium salts [36] We showed that PGAs of DP n = 45 can be obtained by the post-polycondensation of a preformed oligomer in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (BMIm + Tf 2 N -). However, the precipitation of PGA in reaction medium at long reaction times limited the achievable molar mass.…”

Ionic liquids as green reaction media for synthesis of poly(aryl ether ketone)s

“…1,3-dialkylimidazolium-based ILs, which have been the focus of polymer synthesis as environmentally benign solvents [17][18][19], were employed for synthesis of PAEKs. Toluene and anhydrous potassium carbonate were used as azeotroping solvent and salt forming agent respectively.…”