Nonlinear fatty acid terminated polyanhydrides

A systemic study on the synthesis, characterization, degradation, drug rele ase, and stability of nonlinear fatty acid terminated poly(sebacic anhydrid e) (PSA) is reported. Ricinoleic acid was transformed into a nonlinear fatt y acid by esterification with fatty acid chlorides of C8-C18 chain length i n the presence of pyridine. Pure nonlinear fatty acids were obtained by pur ification of the reaction product using column chromatography. Poly(sebacic acid)s terminated with 30 wt % of various nonlinear fatty acids were synth esized by melt condensation to yield waxy off-white materials with molecula r weights in the range of 5000-9000. The terminated polymers are soluble in common organic solvents and melt at temperatures between 70 and 79 degrees C, which allow their fabrication into microspheres and implants. These poly mers degrade into their counterparts during a period of a few weeks while c onstantly releasing an incorporated drug. The incorporation of nonlinear fa tty acid terminals to poly(sebacic anhydride) increased the polymer hydroph obicity and decreased polymer crystallinity when compared to PSA or to line ar fatty acid terminated PSA. The hydrophobic nonlinear side chains retard water from penetrating into the polymer mass, which resulted in higher stab ility and surface erosion front mechanism of polymer degradation and drug r elease.