Synthesis and Characterization of Poly(L-glutamic acid) with High Molecular Weight

Abstract

A high molecular weight poly(L-glutamic acid) (PLGA) was synthesized by the polymerization of γ-benzyl-L-glutama-N-carboxy (BLG-NCA) and by subsequent removal of the benzyl groups. The influence of initiator, monomer/initiator molar ratio, monomer concentration, and reaction temperature of BLG-NCA polymerization upon the molecular weight was investigated. High molecular weight PBLG of 389,000 were achieved at an appropriate combination of all variables. The protecting benzyl groups in the PBLG were removed by hydrogenation with palladium hydroxide on activated charcoal as a catalyst to give a high molecular weight PLGA (molecular weight = 378 000), containing pendant primary carboxyl groups.

Keywords:

• Biomaterials
• Poly(L-glutamic acid)
• Ring-opening polymerization
• Synthesis

ACKNOWLEDGMENTS

Gratitude is expressed to the Young Scientists Fund of the National Natural Science Foundation of China (Grant No. 51003051), Science-Technology Foundation for Middle-aged and Young Scientist of Shandong Province, China (Grant No.BS2011CL021) and the High-level Talent Initial Funding for Scientific Research of Qingdao Agricultural University (Grant No. 630924) for financial support.

Notes

^a The polymerizations run in dioxane solution with triethylamine initiation and monomer/initiator molar ratio of 50 at 30°C.

^b Determined by viscometry.

^a The polymerizations run in dioxane solution at 30°C.

^a The reaction run in a THF/methanol mixture (3:1 v/v).