NAMS 2002 Workshop - ICOM 2008

confirmed by highly efficient re- initiation and successful synthesis of block
copolymers (at preserved high polymer density in swollen state). Influences of
membrane pore diameter, grafting density and chain lengths are currently
systematically investigated, and the results will be discussed and compared with
data of other groups who use non-porous SAM-coated planar inorganic or metal
substrates. The potential of the obtained systems as functional devices will also
be illustrated. For example, by combining temperature-responsive PNIPAAm with
pH- responsive poly(acrylic acid) (as grafted block copolymers, prepared via
grafted poly(tBA)), membrane pores with four distinctly different effective pore
sizes as function of the combination of temperature (25°C vs. 40°C) and pH (2
vs. 7) could be prepared, and those membranes were evaluated with respect to
their barrier properties in diffusion and filtration experiments.
In conclusion, we will demonstrate that the pore space of membranes can be
controlled by grafted functional polymer layers having densities and thicknesses
(between a few to several 100s nanometers), which are pre-determined by well-
defined ‘grafting-from’ reactions such as surface- initiated ATRP. An important
feature is the response of those layers to stimuli, and this can be used to create
‘gates’ or ‘valves’ in the nano- or microscale. The binding to functional groups in
those layers (e.g., immobilization or reversible binding of biomolecules) provides
additional attractive options. The knowledge gained from our model studies with
TEM on the correlations between synthesis, structure and function of such
tailored grafted polymer layers can be transferred to other porous membranes,
and this will enable the preparation of novel membrane-based materials for
advanced separations, controlled release, catalysis and other applications.
[1] M. Ulbricht, Polymer 2006, 47, 2217-2262.
[2] C. Geismann, A. Yaroshchuk, M. Ulbricht, Langmuir 2007, 23, 76-83.
[3] A. Friebe, M. Ulbricht, Langmuir 2007, 23, 10316-10322.