Synthesis of Poly(lactic acid) by Direct Polycondensation of Lactic Acid Using 1,1′-Carbonyldiimidazole, N,N,N′,N′-Tetramethylchloroformamidinium Chloride, and N,N′-Dicyclohexylcarbodiimide as Condensing Agents

Abstract

ABSTRACT:The direct polycondensation of racemic lactic acid using condensing agents, such as 1, 1' -carbonyldiimidazole (CDI), N,N,N',N' -tetrametbylchloroformamidinium chloride (TMCF AC), and N,N' -dicyclohexylcarbodiimide/4-dimethylaminopyridine (DCC(DMAP), was investigated. Reactions using CDI proceeded slightly. Polycondensation using TMCFAC with pyridine gave a polymer in 83% yield, but the number-average molecular weight (.M.) was 3700. Thus, TMCFAC is not effective in the direct polycondensation of lactic acid. However, DCC/DMAP is effective, and polycondensation in dichloromethane at room temperature for 24h afforded poly(lactic acid) having M. of 15400 in 89% yield.

Direct synthesis of poly(l-lactic acid) in supercritical carbon dioxide with dicyclohexyldimethylcarbodiimide and 4-dimethylaminopyridine

“…The molecular weights are comparable to molecular weight of PLA reported by Akutsu and co-workers, synthesised using the DCC/DMAP system in dichloromethane [23], which demonstrates the efficacy of these reagents in scCO 2 . The use of excessive amounts of DCC/DMAP (C3EX) was found to not significantly increase the product molecular weight.…”

“…The synthesis of PLA in dichloromethane was performed as described by Akutsu et al [23]. The yields of products were obtained gravimetrically from purified samples after precipitation.…”

“…The system has been applied to synthesis of graft copolymers [21], and to the copolymerisation of nucleotides with PLA and polyglycolide copolymers [22]. Akutsu et al reported the direct synthesis of racemic PLA with DCC/DMAP in dichloromethane with a molecular weight (M n ) of 15,800 g/mol [23].…”

New Insights into Poly(lactic-co-glycolic acid) Microstructure: Using Repeating Sequence Copolymers To Decipher Complex NMR and Thermal Behavior

“…60,61 In this way, for example, poly LLG was prepared by the DIC/DPTS-mediated condensation of the fully deprotected LLG segmer. All polymers were isolated as colorless solids by precipitation into methanol and purified by re-precipitation from methylene chloride into methanol to give yields ranging from 50 to 99% (Table 2).…”

Polyesters

“…Poly(lactic acid) has been synthesized by direct polyesterification in CH 2 Cl 2 in the presence of DCC and 4-(N ,N -dimethylamino)pyridine. 318 Improved yields and high-molar-mass products have been reported for the polyesterification of various aromatic-aliphatic hydroxy acids in methylene chloride in the presence of the 4-(N ,N -dimethylamino)pyridinium salt of p-toluenesulfonic acid (Scheme 2.33). 315 This salt is assumed to catalyze both the formation of an active Nacylpyridinium species (reaction 1) and the reaction of phenol endgroups with anhydride groups (reaction 2) arising from a possible side reaction of activated carboxylic acid (reaction 3).…”