Large pore size and quasi-order in polyacrylamide gels at high crosslinkercontent

Polyacrylamide gels at high crosslinker content are studied by means of sma ll-angle light scattering. These gels are seen to exhibit a quasi-ordered s tructure, as indicated by the presence of a peak at nonzero angle in the sc attering profiles. The quasi-ordered structure presumably results from a tw o-phase separation phenomenon, induced in the gelling solution by the growt h of crosslinker-rich polymers. Upon the onset of gelation, separation is a rrested. Concentration fluctuations with a typical length scale of a few mi crons are frozen in the gel. As a result, the gel is macroporous.