Anomalous Swelling of a Polystyrene Matrix in Organic Solvents

摘要

Swelling behavior of a commercial linear polystyrene, containing a small amount (<5 wt) of mineral oil, has been studied in three different classes of organic solvents (alkanes, alcohols and carboxylic acids)using both gravimetry and light microscopy. A comparisonhas been made with the results presented in earlier publications using a different linear polystyrene, without mineral oil. It is shown that the polystyrene containing mineral oil absorbs much higher amounts of solvent at lower temperatures then at higher temperatures. Thisanomalous behavior sharply contrasts with the polystyrenewithout mineral oil, which at lower temperatures absorbsmuch less solvent. Light microscopy of the diffusion layerreveals that in the polymer with mineral oil precipitationoccurs during diffusion at low temperatures, but not athigh temperatures. These results clearly show that thepresence of small amounts of mineral oil (in quantitiesbelow the detection limit of FTIR) can cause significantchanges in the sorption behavior of polymers. Theseresults are interpreted by pre-existing nano-inhomogeneities,formed by the mineral oil, limited miscibility of oil inthe polymer phase and high miscibility of solvent in theoil phase.