Novel Amphiphilic block copolymer of Poly (citric acid)-b-Poly (L-lactide)-b- Poly (citric acid) with ABA architecture: Synthesis, Characterization and Micellization

A novel biodegradable amphiphilic ABA block copolymer poly(citric acid)-b-poly(L-lactide)-bpoly( citric acid), (PCA-PLLA-PCA), was synthesizedby melt polycondensation reaction of citric acid and hydroxyl telechelic poly(L-lactide). In this block copolymer, block (B) is linear PLLA and block (A) bringing both hydrophilicity and functional group along the backbone for biomolecule coupling, is poly (citric acid) (PCA) block. Citric acid is a nontoxic metabolic product of the body (Krebs or citric acid cycle), and has been approved by the Food and drug administration of the United States (FDA) for its use in humans. It was found that the citric acid can be reacted with a variety of hydroxyl containing monomers at relatively mild conditions. The chemical structure of the resulting copolymer was characterized by various analytical techniques such as Fourier transform infrared spectroscopy (FT-IR), 1H nuclear magnetic resonance (1H NMR) spectroscopy, gel permeation chromatography (GPC), thermalgravimetry analysis (TGA) and derivative thermal analysis (DTG). The successful preparation of the linear hydroxyl telechelic polylactide and PCAPLLA-PCA block copolymer was confirmed by 1H NMR. In FT-IR spectra of PCA-PLLA-PCA, divided peak of carboxyl groups at 1690-1710 cm-1 is related to hydrogen bonding of carboxylic groups. GPC showed 49% (w/w) for PCA block in copolymer structure, confirmed by TGA diagrams. PCA-PLLAPCA can form polymeric micelles with carboxylic acid functional groups in an aqueous solution with critical micelle concentration (CMC) value of 1.99 ´ 10-3 mg/mL. The micellization was done by N,Ndimethyl formamide/water dialysis method and the average diameter of the obtained polymeric micelles was estimated to be about 79 nm in water by dynamic light scattering (DLS) measurements

کلیدواژه ها:

Block copolymer ، Micelle ، Polylactide