Morphogical and swelling properties of porous hydrogels based on poly(hydroxyethyl methacrylate) and chitosan modulated by ice-templating process and porogen leaching

Abstract

A comparative evaluation of the morphological and swelling properties corresponding to the porous poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels and to the chitosan (CS) hydrogels was developed in this paper. The porous structure of hydrogels based on PHEMA or CS was tailored by ice-templating process and porogen leaching. Poly(methylmethacrylate) (PMMA), as fractionated particles, was used as polymer porogen. The influence of the average size of the fractionated PMMA particles on the internal morphology and swelling properties of the hydrogels was followed. The average pore diameter of PHEMA cryogels increased from 10 ± 2 μm up to 22 ± 5 μm with the increase of the size of the fractionated PMMA particles from below 32 μm up to 50–90 μm. On the other hand, in the case of CS cryogels prepared in the presence of the PMMA particles with different sizes, pores with an average size of 74 ± 6 μm, irrespective of the size of PMMA particles were formed, strong changes being observed in the morphology of the pore walls, these being less compact and, therefore, more accessible for the diffusion of low molecular weight species. Hydrogels based on PHEMA or CS with microchanneled structures arranged along the freezing direction, were generated by unidirectional freezing. The swelling measurements showed that the cryogels prepared in the presence of PMMA particles attained the equilibrium swelling much faster than those prepared without PMMA.