EFFECTS OF POLYMERIZATION VARIABLES ON PLGA PROPERTIES - MOLECULAR-WEIGHT, COMPOSITION AND CHAIN STRUCTURE

In order to study the influence of the variables which control the properties of polylactic-glycolic acid two experiments were conducted according to appropriate experimental designs. The responses studied were yield, weight average molecular weight (GPC), relative proportion of lactic and glycolic acids in the polymer (H-1-NMR) and the ratio of lactic-glycolic to glycolic-glycolic units (C-13-NMR). The variables included in the first study were the relative proportion of lactide and glycolide in the mixture and the concentrations of lauryl alcohol and stannous octoate; the results showed a statistically significant influence of the relative proportions of lactide and glycolide in the mixture and the concentration of lauryl alcohol on the lactic/glycolic proportion in the polymer. The second study involved time, temperature and lauryl alcohol concentration as variables. The findings showed a statistically significant negative effect of temperature on weight average molecular weight and of temperature, time and time-temperature interaction on yield. Ratios between lactic-glycolic and glycolic-glycolic units ranged from 1:1 to 1:4. None of the variables studied had any effect on this characteristic.