Synthesis and characterization of amphiphilic biodegradable poly(glutamic acid‐co‐lactic acid‐co‐glycolic acid) by direct polycondensation

Poly(glutamic acid‐co‐lactic acid‐co‐glycolic acid) (PGLG), an amphiphilic biodegradable copolymer, was synthesized by simply heating a mixture of L‐glutamic acid (Glu), DL‐lactic acid, and glycolic acid with the present of stannous chloride. The unique branched architecture comprising of glutarimide unit, polyester unit, and polyamide unit was confirmed by NMR spectrum. The PGLG was soluble in many organic solvents and aqueous solution of sodium hydroxide (pH ≥ 9.0). The thermal properties were evaluated using thermogravimetric analysis and differential scanning calorimetry. Molecular weights were determined by 1H NMR end‐group analysis and GPC, respectively, and the results indicated that the higher Glu content resulted in a decrease of the molecular weight.