Effects of cryogenic condition and chemistry on the properties of synthetic and biopolymer cryogels

Abstract

We discuss here the properties of seven different synthetic and biopolymer cryogels prepared under identical conditions, and how the cryogenic condition and chemistry affect their properties. The monomers used in the study are acrylamide (AAm), N, N-dimethylacrylamide (DMAA), sodium acrylate (NaAA), sodium methacrylate (NaMA), and 2-acrylamido-2-methylpropane sulfonic acid sodium salt (AMPS). Silk fibroin (SF), and double-stranded deoxyribonucleic acid (DNA) are selected as the biopolymers for the preparation of the cryogels. The nonionic monomers AAm and DMAA produce cryogels with the largest total pore volumes and average pore diameters while ionic cryogels exhibit a small pore volume due to the collapse of the pores during their drying. Moreover, SF cryogel has the most mechanically stable porous structure followed by AAm and DMAA cryogels. The experimental findings can be explained with the cryogenic conditions namely, the total ice volume in the cryogelation system and the true concentration of the monomers or polymers in the unfrozen domains after cryoconcentration, as determined from DSC measurements. The extent of cryoconcentration and hence the true concentration of the monomers or polymers regulate the mechanical stability of the cryogel pore walls.