Synthesis and characterization of a novel drug-loaded polymer, poly(lactic acid-co-aminomethyl benzimidazole)

Using aminomethyl benzimidazole (AMB) as a model of benzimidazole-type drugs, a potential biodegradable drug-loaded polymer poly(lactic acid-co-aminomethyl benzimidazole) (PLAAMB) is synthesized as designed via direct melt polycondensation starting from d,l-lactic acid (LA). When the molar feed ratio LA/AMB is 40/1, the optimal synthetic conditions, including catalyst type and dosage, polycondensation temperature, and copolymerization time are discussed. After the prepolymerization at 140 °C for 8 h, using 0.4 wt% stannous oxide (SnO) as the catalyst, the melt copolymerization at 160 °C for 6 h gives the copolymer with the biggest weight-average molecular weight (Mw) 5300 Da. The structure and properties of the copolymer are systematically characterized with Fourier transform infrared, 1H NMR, gel permeation chromatography, differential scanning calorimetry, and X-ray diffraction. And the investigations on the influences of different molar feed ratios on the properties of PLAAMB show that, the copolymer PLAAMB with the biggest Mw of 9400 Da can be obtained. After the drug model AMB as a monomer is introduced into polylactic acid during the condensation, the Tg of the obtained PLAAMB is lower than the Tg of homopolymer poly(d,l-lactic acid) (PDLLA). The Mw and crystallinity of PLAAMBs can meet the requirement of drug-loaded polymers in the drug delivery.