Effect of Pore-Forming Agent Type on Swelling Properties of Macroporous Poly(N-[3-(dimethylaminopropyl)]-methacrylamide-co-acrylamide) Hydrogels

Macroporous poly(N-[3-(dimethylaminopropyl)]methacrylamide-co-acrylamide) [P(DMAPMA-co-AAm)] hydrogels were prepared by free-radical crosslinking copolymerization of corresponding monomers in water using two different pore-forming agents such as hydroxypropyl celluose (HPC) and poly(ethylene glycol) (PEG). The effect of these pore-forming agents on the volume phase transition temperature (VPT-T), interior morphology and swelling/deswelling kinetics of the P(DMAPMA-co-AAm) hydrogels was investigated. Scanning electron micrographs revealed that the interior network structure of the hydrogel matrix became more porous due to the presence of HPC or PEG pore-forming agents. The more porous matrix provided numerous water channels for water diffusion in or out of the matrix and, therefore, an improved response rate to the external stimuli. Particularly, due to its unique macroporous structure, the PEG-modified hydrogel showed a tremendously faster response to the external temperature changes during deswelling process and the swelling process at 22°C.