Fatty acid terminated polyanhydrides

A systematic study on the synthesis, characterization, degradation, and dru g release of fatty acid terminated poly(sebacic acid) (PSA) is reported. Fa tty acid terminated sebacic acid polymers were synthesized by melt condensa tion of acetate anhydrides of linear fatty acids (C8-C18) and sebacic anhyd ride oligomers to yield waxy off-white materials. Polymers with molecular w eights (M-w) in the range of 9,000 and 5,000 were obtained for the 10% and 30% (weight ratio) containing fatty terminals, respectively. Up to about 30 % of fatty acid terminals, the final product is mainly fatty terminated pol ymer with up to about 5% w/w of the symmetric fatty anhydride. Increasing a mounts of fatty acid acetate anhydride in the polymerization mixture had li ttle effect on the polymer molecular weight up to a ratio of 40 : 60 (fatty acid acetate : sebacic acid oligomer) which remains in the range of 5,000- 8,000. Above this ratio the molecular weight dropped to a level of 2,000-3, 000 and the percent of the symmetric anhydride increased to 10-40%. The fat ty terminals had little effect on PSA melting point and crystallinity. Howe ver, the fatty terminals had a significant effect on the polymer degradatio n and drug release rate. PSA with 30% w/w of C14-C18 terminals degraded and released the incorporated drug for more than 4 weeks as compared with 10 d ays for the acetate-terminated PSA. (C) 1999 John Wiley & Sons, Inc.