Macroporous elastic polyacrylamide gels prepared at subzero temperatures:: control of porous structure

Macroporous polyacrylamide gels (MPAAGs) with unique elastic morphology and open porous structure are prepared at subzero temperatures. The porous structure of MPAAGs consisting of large, 1 - 100 mu m-sized interconnected pores, is controlled by the freezing temperature, the content of the initiator system ( ammonium persulfate and N,N,N',N'-tetramethyl-ethylenediamine) in the initial reaction mixture and the solvent used. The initiator content, through its effects on the kinetics of polymerization, is an efficient tool of control allowing for the preparation of well defined macroporous elastic structures with either open interconnected pores or closed pores. In the semi-frozen reaction mixture, the dissolved monomers and initiators are concentrated in the unfrozen liquid microphase where the polymerization reaction proceeds. The final freezing temperature, T-f ( defined as temperature fixed in a low temperature thermostat), as well as the solvent used affect the porous structure through their effect on the formation of the unfrozen liquid microphase.