Controlled Release of 5-Aminosalicylic Acid (5-ASA) from New Biodegradable Polyurethanes

Segmented polyurethanes containing azo aromatic groups in the main chain were synthesized by reaction of 3,3′-azobis(6-hydroxybenzoic acid) (ABHB), 5-[4-(hydroxyphenyl)azo] salicylic acid (HPAS), and 5-[1-hydroxynaphthyl)azo] salicylic acid (HNAS) with hexamethylenediisocyanate (HDI). All synthesized monomers and polymers were characterized by elemental analysis, FTIR, (1)H-NMR spectra, TGA and DSC analysis. All the synthesized azo polymers showed good thermal stability and the onset decomposition temperature of all these polymers was found to be above 195 °C under nitrogen atmosphere. The release of 5-ASA under physiological conditions (pH = 7.8 and pH = 1.5) was investigated at body temperature (37 °C). The release rate of 5-ASA increased with increasing pH (i.e., 7.8 > 1.5).