Use of contrast-enhanced small-angle neutron scattering to monitor the effects of solvent swelling on the pore structure of styrene-divinylbenzene resins

The pore structure of series of porous styrene-divinylbenzene resins has been monitored both in the non-swollen state and when swollen with a range of solvents of varying Hildebrand solubility parameter using small-angle neutron scattering. It has been shown that the Pored scattering invariants increase as swelling increases, indicating an increase in the interfacial scattering surface area. For the sample prepared with a relatively small amounts of porogen during polymerization, the scattering curves of the acetic acid and toluene swollen samples each consist of two linear regions up to ca. 45 Angstrom is size, corresponding firstly to scattering from swollen, highly crosslinked regions and secondly to mass fractal aggregates of these regions. Samples produced with higher amounts of porogen have a surface fractal structure in the swollen state. Porosity that is closed to the external surface in dry samples is accessible to swelling solvents.