Synthesis, characterization and rheological behavior of pH sensitive poly(acrylamide-co-acrylic acid) hydrogels

Poly(acrylamide-co-acrylic acid) poly(AAm-co-AAc) hydrogels were prepared by free radical polymerization initiated by redox initiators of ammonium peroxodisulphate (APS) and N,N,N′,N′-tetramethyl ethylene diamine (TEMED); N,N′-methylene bisacrylamide (BIS) was employed as a crosslinking agent. The copolymers were characterized by infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), dynamic rheology and swelling measurements. Results indicated that the strong interaction in the hydrogels resulted in the formation of a more stable copolymer. The single glass transition temperature (Tg) in sample suggested that the two polymers into the hydrogel have a good miscibility. The elastic modulus (G′) and linear viscoelastic region increased with increase in PAAc concentration. The oscillation time sweep study of the hydrogels exhibited a flat G′ indicating a stable structure and good mechanical strength. In the swelling measurements, the gels exhibited appreciable water uptake and were highly sensitive to pH environment. So the poly(AAm-co-AAc) hydrogel will have promising application in pharmaceutical use and in biomaterials.