Synthesis of macroporous thermosensitive hydrogels: a novel method of controlling pore size.

Macroporous thermosensitive poly(N-isopropylacrylamide) hydrogels were synthesized in the presence of dodecyl dimethyl benzyl ammonium bromide (DDBAB). Poly(vinyl alcohol) (PVA) was involved to control the pore size of the hydrogels. The morphology of the resulting hydrogels was studied by both an optical microscope and a scanning electron microscope. Moreover, the pore size and its distribution were examined by mercury intrusion porosimetry. The results indicated that size of the pores decreased with the increase of the amount of PVA added. The mechanism was explained after dynamic light scattering measurement of the size of hydrophobic initiator DDBAPS aggregates that were formed in situ in PVA aqueous solutions of various concentrations as the product of the reaction between DDBAB and the water soluble initiator ammonium persulfate. Swelling ratio and deswelling/reswelling kinetics of the hydrogels were also measured to investigate the response properties of the hydrogels. It would be a promising method of pore size control for synthesizing hydrogels of other vinyl monomers that could be initiated by persulfates.