New biodegradable polyurethanes containing azo-linked polymeric prodrugs of 5-aminosalicylic acid (5-ASA) in the main chain were prepared by reacting 1,6-Hexamethylenediisocyanate (HDI) with 3,30-azobis(6-hydroxy benzoic acid) (ABHB) and 5-[4-(hydroxyl phenyl) azo] salicylic acid (HPAS) as azo derivatives of 5-ASA. The polymers were characterized by FTIR and 1H-NMR spectroscopy. The hydrolysis of polyurethane containing azoderivatives of 5-ASA was carried out in cellophane membrane dialysis bags containing aqueous buffer solution (pH 1/4 8.5 and pH 1/4 1) at 37 C. Detection of the hydrolysis product by UV spectroscopy showed that ABHB and HPAS were released by the hydrolysis of the urethane bond in the polymer chain.

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A series of acrylic terpolymers containing silyl pendant groups was prepared by free radical cross-linking copolymerization. Me 3 Si, Et 3 Si and t-BuMe 2 Si together with cubane-1, 4-dicarboxylic acid (CDA) were covalently linked with 2-hydroxyethyl methacrylate (HEMA). The silyl-linked HEMA are abbreviated as TMSiEMA, TESiEMA and TBSiEMA respectively. Cubane-1, 4-dicarboxylic acid (CDA) linked to two HEMA group is the cross-linking agent (CA). Free radical cross-linking terpolymerization of the methyl methacrylate (MMA) and methacrylic acid (MAA) with two different molar ratios of organosilyl monomers and CA was carried out at 60-70 • C. The compositions of the cross-linked three-dimensional polymers were determined by FT-IR spectroscopy. The glass transition temperature (Tg) of the network polymers was determined calorimetrically. The Tg of network terpolymers increases with increasing of cross-linking degree. Equilibrium swelling studies were carried out in enzyme-free simulated gastric and intestinal fluids (SGF and SIF, respectively). The gels swelled more in SIF than in SGF. The swelling behaviour of the copolymers was dependent on the content of MAA groups and caused a decrease in gel swelling in pH 1 or an increase in gel swelling in pH 7.4. Based on the great difference in swelling ratio at pH 1 and 7.4 for P-1, P-6 and P-10 appear to be good candidates for colon-specific drug delivery.

Attaching the organosilyl groups to macromolecular chains of 2-hydroxyethyl methacrylate (HEMA) should lead to important modifications of polymer properties. t-BuMe 2 Si and cubane-1,4-dicarboxylic acid (CDA) were covalently linked with 2-hydroxyethyl methacrylate (HEMA). The silyl-linked HEMA is abbreviated as TSMA, while cubane-1,4-dicarboxylic acid (CDA) linked to two HEMA groups is the cross-linking agent (CA). Free radical cross-linking copolymerization of TSMA and HEMA with various ratios of CA as the cross-linking agent was carried out at 60-70 o C. The compositions of the cross-linked, three-dimensional polymers were determined by FTIR spectroscopy. The glass transition temperature (T g ) of the network polymers was determined calorimetrically. The T g of the network polymer increased with increasing cross-linking degree.

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