NAMS 2002 Workshop - ICOM 2008

Nanostructured Membranes I – 5
Monday July 14, 4:30 PM-5:00 PM, Moloka’i
Polymers of Intrinsic Microporosity in the Application of Organic Solvent
Nanofiltration
K. Heinrich (Speaker), GKSS Research Centre Geesthacht GmbH, Germany
D. Fritsch, GKSS Research Centre Geesthacht GmbH, Germany, fritsch@gkss.de
P. Merten, GKSS Research Centre Geesthacht GmbH, Germany
G. Bengtson, GKSS Research Centre Geesthacht GmbH, Germany
S. Dargel, GKSS Research Centre Geesthacht GmbH, Germany
Nanofiltration of aqueous solutions is a well developed method in industrial
applications because it saves energy and costs. For non- aqueous, i.e., organic
solvent nanofiltration (OSN) only a very few membranes are on the market
available. Widely in use nanofiltration membranes for reverse osmosis are not
stable against organic solvents. New kinds of polymers are the polymers of
intrinsic microporosity (PIM polymers) [1] which shows superior properties
concerning OSN. These are ladder-type poly(ether)s with a stiff backbone and a
contorted structure that cannot pack closely and lead to a high free volume
accompanied by a high surface area. They are only soluble in tetrahydrofurane
and some halogenated solvents and are stable against many organic solvents
without cross-linking. In this work composite membranes of PIM-1 and newly
synthesized co-polymers were tested. The PIMs were prepared by
polycondensation reaction from dicyanotetrafluorobenzene and
tetrahydroxytetramethylspirobisindane [2] . Co- polymers were synthesized by
analogous polycondensation with of a variety of new co- monomers. The
synthesized polymers were characterized by size exclusion chromatography
(SEC), NMR, IR, elemental analysis, density and permeability measurements.
The fractional free volume was calculated from the density data. For preparation
of composite membranes different membrane supports were applied, such as,
poly(acrylonitrile) (PAN), cross-linked poly(acrylonitrile-co-glycidyl methacrylate)
(PANGMA) and poly(vinyliden-fluoride) PVDF. Fillers were added to improve the
nanostructered materials. Hexaphenylbenzene (HPB, MW = 534,71g/mol) was
used as a model compound to test the retention in different solvents. The results
show high fluxes in the range of 5 to 10 l/m²hbar and retentions up > 90%.
[1] Peter M. Budd et al., Adv. Mater. 2004, 16, 456.
[2] Kricheldorf et al., J. Polym. Sci. Part A.: Polym. Chem. 2006, 44, 5344 -5352.