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 pro perties of polylactic-glycolic acid two experiments were conducted acc ording 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 la ctic-glycolic to glycolic-glycolic units (C-13-NMR). The variables inc luded in the first study were the relative proportion of lactide and g lycolide in the mixture and the concentrations of lauryl alcohol and s tannous octoate; the results showed a statistically significant influe nce of the relative proportions of lactide and glycolide in the mixtur e and the concentration of lauryl alcohol on the lactic/glycolic propo rtion in the polymer. The second study involved time, temperature and lauryl alcohol concentration as variables. The findings showed a stati stically significant negative effect of temperature on weight average molecular weight and of temperature, time and time-temperature interac tion on yield. Ratios between lactic-glycolic and glycolic-glycolic un its ranged from 1:1 to 1:4. None of the variables studied had any effe ct on this characteristic.