Synthesis and characterization of ethylenediamine modified poly (DL-lactic acid)

Hydrophobicity and increased acidity due to degradation are two fatal shortcomings for poly (lactic acid) (PLA) to be used in biomedical areas. Many chemical modifications have been done to improve its hydrophilicity, but the increased acidity is still a problem. Although introduction of basic salts into PLA by physical blending is a technique to control the pH in local environment of PLA, it could not essentially address the problem of increased acidity. Here we synthesized ethylenediamine modified poly (DL-lactic acid) (EMPLA) by the N-acylation of anhydrides in MPLA (maleic anhydride modified poly (DL-lactic acid)) with ethylenediamine, whereby basic ethylenediamine could neutralize the acidic degrading products of PLA. In this paper, the synthesis and purification of EMPLA were reported in detail, and ninhydrin reaction, DSC, FT-IR, ¹³C-NMR and ¹H-NMR were used to characterize EMPLA. The obtained results show that ethylenediamine could be covalently introduced into MPLA by the developed synthetic method, which provides technical and material supports for further detecting biodegradability and biocompatibility of EMPLA and finally applications in biomedical areas.