Structural aspects of porous gels

The mode of formation and the structure of both chemically and physically crosslinked polymer gels are discussed. For both types elastic and porous ones are compared. The chemically crosslinked gels from trimethylolpropane trimethacrylate (TRIM) are interesting because of their narrow distributions of small pores (radii 20 Å) when polymerized in toluene. The large pores (200 Å) on the other hand varied with concentration as could be expected. One of the ways to obtain porosity for physically cross‐linked gels is to cool solutions of polymers in certain solvents mixtures. Thus, polyacrylonitrile (PAN) yields porous gels when cooling solutions thereof in dimethyl‐formamide/water mixtures. By NMR, DSC, and X‐ray diffraction evidence has been obtained of ordered structures which at least partially exist even above the gel melting temperature.