Abstract
pH sensitive hydrogels containing azoaromatic crosslinks were synthesized by a polymer‐polymer reaction. To minimize cyclization, a three step synthesis was employed. First, a polymeric precursor (P‐ONp) containing side‐chains terminated in reactive p‐nitrophenyl ester groups was synthesized by free radical precipitation copolymerization of N,N‐dimethylacrylamide, acrylic acid, N‐tert‐butylacrylamide, and N‐methacryloylglycylglycine p‐nitrophenyl ester. In the second step, the p‐nitrophenyl ester groups of P‐ONp were converted to NH~2~ groups (P‐NH~2~) by a polymer‐analogous reaction with an excess of a diamine, namely N,N′‐(ω‐aminocaproyl)‐4,4′‐diaminoazobenzene. The hydrogel was then prepared in the third step by a polymer‐polymer reaction of P‐ONp with P‐NH~2~. The linear copolymers were characterized by the content of functional groups and molecular weights. The hydrogels were characterized by equilibrium degree of swelling, modulus of elasticity in compression at pH 7.4, the network structure, and in vitro degradability. The swelling, mechanical properties, and rate of degradation depended on the crosslinking density. Although we were able to restrict cyclization, other side reactions such as unreacted pendent groups and hydrolysis need to be controlled. These hydrogels have potential for colon‐specific drug delivery.