Homogeneous,
highly porous, low density, open cell polymer foams were prepared by
polymerizing the continuous phase of HIPEs (high internal phase emulsions)
containing monomers such as styrene (S), divinylbenzene (DVB), 2-ethylhexyl
methacrylate (EHMA), 2-ethylhexyl acrylate (EHA) and perfluorooctylethyl
methacrylate. The structure, thermal properties and mechanical properties of
the foams were characterized and their interactions with water and haloorganics
were evaluated. The cell diameters of the polyHIPEs ranged from 1.5 to 15 mm, the intercellular pore diameters
from 0.3 to 1.5 mm,
the densities from 0.05 to 0.15 g/cm3 and the surface areas from 7.0
to 132.0 m2/g. The glass transition temperatures (Tg) and
compressive moduli of the polyHIPE were similar to those expected from
literature. Copolymer foams with low S contents were more elastomeric (Tgs
below 25°C) whereas foams with high S contents were rather brittle (Tgs
above 25°C). Increasing the crosslinking comonomer (DVB) content caused an
increase in Tg and in brittleness. Two methods were used in an attempt to
increase the surface areas of the polyHIPE: (a) soxhlet extraction with water
and methanol; (b) the addition of up to 50% of a solvating porogen, toluene, in
the organic phase. The removal of a halo-organics from water using
polyHIPE sorbents was studied by performing kinetic (rate) and equilibrium
experiments. Important process design parameters were calculated from both the
sorption isotherms and from the batch experiment kinetics: the feasibility of
sorbing a specific sorbate, the sorbent capacity, and the quantity of sorbent
required to achieve a given degree of sorbate removal. The rate and isotherm
studies showed that there were only small differences in the amounts of
bromoform sorbed by the P(S/DVB), P(EHMA/DVB) and P(EHA/DVB) polyHIPE, none of
which underwent Soxhlet extraction. P(S/DVB) polyHIPE that underwent Soxhlet
extraction exhibited significant increases in surface area, from 7.9 to 28.9 m2/g,
and in the amount of bromoform absorbed, from 19 to 32 mg/g. When toluene
is used as a solvating porogen the cell wall is rough and contains pores
ranging from 5 to 100 nm in diameter. Extraction increased the surface area by
about 20 fold and the sorption capacity by about 200 fold. This research has
shown that polyHIPE exhibit great potential as sorbents for the removal of
haloorganic contaminants from water.
