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Weiche Materie Poster: Do., 13:00–15:30 D-P349
Small Angle X-ray Scattering Studies on Mesoporous Organic-Inorganic
Proton-Conductors Based on 2,5-diaminobenzenesulfonic acid.
Luis Antonio Sanchez de Almeida Prado 1 , Suzana Pereira Nunes 2 , Sergio
S. Funari 3 , Karl Schulte 1
1 Technische Universität Hamburg-Harburg, Polymer Composites (AB 5-09),
Denickestrasse 15, Geb. 2B, D-21073 Hamburg. – 2 GKSS, Forschungszentrum, Institut
für Polymerforschung, Max-Planckstrasse 1, D-21520, Geesthacht. – 3 HASYLAB
at DESY, Notkestr. 85, D-22603 Hamburg.
The development of new inorganic materials with good thermal stability and high
proton-conductivity gained an additional importance due to their potential application
as additives for polyelectrolyte membranes for fuel cells. Recently, it was proved that
the incorporation of mesoporous molecular sieves (MCM-41) caused an improvement of
the methanol barrier properties of polyelectrolyte membranes for DMFC applications
[1]. Even better results could be achieved after the surface modification of MCM-41
with proton-conducting groups derived from imidazole rings attached to organosiloxanes
[1]. The use of sulphonated oxadiazole-based telechelics as modifiers of organically
modified silicas (ormosils) containing C-Br bounds at the surface, lead to membranes
with improved proton-conductivity and stability at temperatures higher than 373 K
[2].
In the present communication, the very first results concerning the preparation and
structural characterisation of sulphonated MCM-41 are presented. These organicinorganic
materials were prepared by hydrolysis and condensation of a silica source
and a sulphonated alkoxysilane (SAS). The aforementioned alkoxysilane was produced
in situ via reaction between 2,5-diaminobenzenesulfonic acid and 3-glycidyloxypropyltrimethoxysilane
(GLYMO). SAXS experiments were carried out at A2 beamline at
HASYLAB (DESY) in order to confirm the formation of the MCM-41 mesophase.
It was observed that the polycondensation of the sulphonated alkoxysilane did not
produce any meso-structured material even in the presence of surfactant micelles as
templates. However, the combination of the sodium metasilicate and the SAS enable
the production of materials with a well-ordered hexagonal array of cylindrical pores
(MCM-41), which were stable after the removal of the template by ethanol:heptane
acidic mixtures. This extraction with acidic mixture leads to the partial removal of the
sulphonated alkoxysilane moieties. On the other hand, the co-polymerisation between
the SAS and tetramethoxysilane produced materials with less-ordered array of pores,
although little extraction of AS could be observed after the removal of the template
by the acidic ethanol:heptane mixture. New experiments are been currently carried
out in order to optimize the reaction between sodium metasilicate and SAS aiming at
developing of meso-structured materials with higher functionalization degrees.
The authors acknowledge HASYLAB for the SAXS measurements (Project II-04-072).
[1] C.S. Karthikeyan et al., J. Membrane Sci 254 (2005) 139.
[2] D.Gomes et al., J. Polym. Sci. Polym. Phys. Ed. (2006) (submitted).