Synthesis, characterization, biodegradation, and drug delivery applicationof biodegradable lactic/glycolic acid polymers I. Synthesis and characterization

A series of lactic/glycolic acid polymers with various molar ratios of lact ic to glycolic acid and various molecular weights were synthesized using th e ring-opening polymerization method. The polymerization conditions for the lactic/glycolic acid polymer synthesis were as follows: 150 degrees C, 700 mu m Hg, 3 h, 0.03 wt% of catalyst (stannous 2-ethyl-hexanoate) concentrat ion. The molecular weight of these polymers was controlled by using a molec ular weight controller, lauryl alcohol. The synthesized polymers have been characterized with respect to polymer co mposition, molecular weight, inherent viscosity, and glass transition tempe rature. The characterization experiments show a good correlation between th e polymer compositions and the feed ratios of lactic to glycolic acid. The molecular weight of the lactic/glycolic polymers, ranging from 10 876 to 16 6 630 D and the intrinsic viscosity of the polymers, ranging from 0.16 to 0 .86 dl g(-1), are controlled by the amount of molecular weight controller u sed. The effect of the amount of the molecular weight controller on the pol ymer molecular weight and the polymer inherent viscosity was studied. Resul ts indicate that the molecular weight and inherent viscosity of the polymer s have a log-log linear relationship with the amount of molecular weight co ntroller used. The lactic/glycolic acid polymers are amorphous, glassy, and transparent. The glass transition temperature of the polymers range from 2 1.95 to 51.29 degrees C, depending on the polymer molecular weight and the composition.