Investigation of pH-dependent swelling behavior and kinetic parameters of novel poly(acrylamide-co-acrylic acid) hydrogels with spirulina

Abstract

Poly(acrylamide-co-acrylic acid)-spirulina (AAm-AAc-Sp) hydrogels were prepared by free radical solution polymerization of the monomer acrylamide (AAm) and the comonomer acrylic acid (AAc) with N,N-methylene bisacrylamide (BAAm) as the crosslinker in the presence of spirulina (Sp), which is a microalga species. The swelling ratios of the hydrogels were followed by gravimetric measurements. Hence, swelling kinetics and diffusion parameters were determined. Furthermore, the morphological structures and mechanical behaviors of the hydrogels were investigated by scanning electron microscopy and by using a uniaxial compression machine, respectively. All the results showed that spirulina had strong influence in the pH-dependent swelling behavior, as well as on the kinetic and diffusion parameters due to its interaction with the acrylic acid units. These interactions were attributed to spirulina, which caused a change in pore size and its distribution. The present novel hydrogels showed high swelling at neutral pH, but collapsed slowly at low and high pH values. Thus, these AAm-AAc-Sp hydrogels can be good candidates for pH-sensitive drug delivery systems.