versatile approach to develop porous hydrogels with a regular pore distribution and investigation of their physicomechanical properties

Porous polyacrylamide (PAAm) hydrogels with enhanced mechanical properties and regular pore distribution have been synthesized by a unique and facile methodology, which involves formation of the hydrogel pores by leaching out chemically modified silica particles. To improve the pore distribution and mechanical properties of the hydrogel network, porogen particles have been modified with PAAm chains chemically attached to the silica surface. Grafting polymerization initiated by peroxide groups immobilized on the particle surface has been used for this modification. The grafted PAAm layer on the silica surface improves the dispersibility of the porogen material in the hydrogel composition, and simultaneously forms pore "walls" reinforcing the hydrogel network, after leaching out the silica particles. The proposed synthetic way for the development of porous hydrogels includes three steps: (i) tethering of PAAm chains to silica particles due to the grafting polymerization initiated by an adsorbed polyperoxide macroinitiator (PPM), (ii) simultaneous crosslinking of grafted PAAm chains and PAAm forming hydrogel network, and (iii) pore formation by leaching out silica particles in the presence of hydrofluoric acid. The PPM has been synthesized by a free radical copolymerization of the peroxide monomer (PM) N-(tert-butylperoxymethyl)acrylamide with acrylamide. Both PM and PPM have been developed in our lab, and applied for the synthesis of porous polymeric hydrogels.