Cryogenic formation-structure-property relationships of poly(2-acrylamido-2-methyl-1-propanesulfonic acid) cryogels

Abstract

Cryogelation is a simple and eco-friendly technique to produce macroporous cryogels exhibiting extraordinary mechanical properties. Most of the results on cryogels reported so far, however, lack a more detailed analysis to provide real conditions of the cryogelation system, which is an apparently frozen reaction solution. We investigate here the correlations between the cryogelation conditions and properties of poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) cryogels, which are attractive materials with a wide range of application areas. PAMPS cryogels are prepared by free-radical copolymerization of AMPS and N,N′-methylenebis(acrylamide) (BAAm) in aqueous solutions at −18 °C in the presence of a redox initiator system. The total pore volume of the cryogels decreases whereas the average pore diameter increases with increasing AMPS concentration Co. The morphological variations depending on Co could be explained with the local conditions during cryogelation, i.e., the melting temperature of the reaction solution, the ice volume, and the true concentration of the monomers in unfrozen domains. PAMPS cryogels prepared at 9.1 mol % BAAm exhibit the highest modulus (0.73 ± 0.05 MPa) and could withstand up to 6.0 ± 0.5 MPa compressive fracture stress.