NAMS 2002 Workshop - ICOM 2008

Gas Separation I – 3
Monday July 14, 10:45 AM-11:15 AM, Kaua’i
Segmented Block Copolymers: A Molecular Toolbox to Tailor the Mass
Transport Properties of Polymeric Nanocomposites
S. Reijerkerk (Speaker), University of Twente, The Netherlands, s.r.reijerkerk@utwente.nl
A. IJzer, University of Twente, The Netherlands
A. Araichimani, University of Twente, The Netherlands
R. Gaymans, University of Twente, The Netherlands
K. Nymeijer, University of Twente, The Netherlands
M. Wessling, University of Twente, The Netherlands
The removal of CO2 from light gas mixtures such as H2, N2 and CH4 is an
important application in industry, for instance in synthesis gas, flue gas and
natural gas processing. Poly(ethylene oxide) (PEO) based block copolymers
have been studied extensively as membrane material for these CO2/light gas
separations. In general, block copolymers contain a phase separated
morphology in which the hard segments (usually polyamides, polyurethanes or
polyimides) provide mechanical stability and the soft segments control the gas
transport properties. The polar ether oxygen linkages in PEO interact favorable
with the quadrupolar CO2, resulting in high CO2/light gas solubility selectivities.
Simultaneously the flexible ether oxygen linkages ensure high CO2 diffusivities
and thus high CO2 permeabilities.
Incorporation of high concentrations of PEO is however difficult due to its strong
tendency to crystallize, which is detrimental for the permeation properties. This is
especially evident at ambient and sub ambient temperatures. Crystallization at
sub ambient temperatures is especially disadvantageous for CO2/CH4
separations, as these separations often occur offshore and because higher
hydrocarbons in natural gas are usually removed by condensation at low
temperatures, thus reducing the need for reheating such a gas stream.
Furthermore, the non-uniform nature of the hard segments usually used, leads to
inefficient phase separation of the soft and hard segments, which has reduced
the CO2 permeability and the mechanical strength. High hard segment
concentrations (> 30 wt%) are thus required to guarantee mechanical strength,
but at the same time reduce the gas permeability.
Here, we report the synthesis, characterization and gas permeation properties of
a series of segmented block copolymers based on a soft segment containing a
random distribution of 75 mol% PEO and 25 mol% poly(propylene oxide) (PPO)
with strongly improved phase separation and a significant reduction in
crystallinity of the soft segment. The crystallization of the ethylene oxide units is
suppressed due to the presence of the methyl side groups of PPO, that are
randomly distributed along the polymer backbone and which prevent regular