Influence of hypercrosslinking on adsorption and absorption on or in styrenic polymers

摘要

Hypercrosslinking of swollen resins can substantially modify their sorption properties. This effect was investigated on three series of polymers with different degree of hypercrosslinking prepared from gel-type and macroreticular precursors. The sorption properties were characterized by measurements of sorption isotherms of aromatic hydrocarbons (benzene, toluene, ethylbenzene and 2-methylpropyl benzene) from methanol and water. This made possible to assess sorption processes both at high sorbate concentrations and at conditions close to possible practical applications. In the evaluation of sorption it is necessary to take into account both adsorption (the accumulation of sorbate on the border between polymer and fluid phase) and absorption of sorbate into the polymer matrix. Importance of the adsorption mechanism increases with the increase of the hypercrosslinking degree. Due abundance of narrow micropores in the hypercrosslinked materials, the adsorption in is not a classical surface phenomenon but the sorbate molecules rather fill the pore volume. At sorbate concentrations approaching the saturation, in the macroreticular polymers the pore filling is extended even to mesopores. This seems to be a phenomenon similar to the capillary condensation in gas-solid systems.