Preparation of polyacrylamide-based supermacroporous monolithic cryogel beds under freezing-temperature variation conditions

Continuous supermacroporous monolithic cryogel is a novel sponge-like chromatographic adsorbent for bioseparation in downstream process and it is always prepared under a constant freezing-temperature condition. In this work, polyacrylamide-based supermacroporous monolithic cryogel beds in different inner diameter glass columns (I.D. 10, 16 and 26 mm) have been prepared by radical cryogenic copolymerization process under the condition of freezing-temperature variation. The matrix microstructure morphologies of these cryogels were analyzed by scanning electron microscopy (SEM) and the axial liquid dispersion characteristics in these cryogel beds were also analyzed by measuring the residence time distributions (RTDs). The formation of cryogel bed under the present situation has been considered as a coinstantaneous process of solvent crystal growth and polymeric monomer copolymerization. Effects of freezing-temperature variation route, cooling rate and redox initiator concentration on the cryogel microstructure and the liquid dispersion characteristics were investigated experimentally to reveal the cooperative mechanisms of these two processes on the formation of cryogel bed. The results showed that the cryogel pore-structures and the axial liquid dispersion coefficients in the cryogel beds depended strongly on the cooling condition, which controls the solvent crystallization process, and the redox initiator concentration, which influences the monomer polymerization.