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Porous Polymer Films and Honeycomb
Structures Made by the Self-Organization of
Well-Defined Macromolecular Structures
Created by Living Radical Polymerization
Techniques**
Martina H. Stenzel-Rosenbaum, Thomas P. Davis,*
Anthony G. Fane, and Vicki Chen
Macroporous polymers have become materials of high
interest in recent years, because of their potential applications
in diverse areas from membranes to medical devices.[1] Star
and block polymers are known to template around water
droplets to form isoporous arrays.[2±5] However, the utilization
of this discovery has been severely restricted because the
synthetic route used, anionic polymerization, is difficult and
limited to a small number of (generally nonfunctional)
monomers. A number of other synthetic routes to star
polymers have become available in recent years,[6] and the
development of living radical polymerization provides a great
opportunity to significantly broaden the range of functional
materials. We have adopted both metal-mediated radical
polymerization and reversible addition ± fragmentation trans-
fer (RAFT) polymerization to synthesize star polymers for
application in isoporous film and honeycomb-structure pro-
duction. The porous structures are created from casting
solutions of star polymers in an organic solvent onto a glass
substrate under a humid atmosphere as described by Francois
and co-workers.[4, 7, 8]
 Ã
[6] a) P. Schnider, G. Koch, R. Pretot, G. Wang, F. M. Bohnen, C. Krüger,
The star polymers were synthesized either by metal-
mediated polymerization using a copper (atom-transfer
radical polymerization, ATRP) or an iron catalyst system or
by RAFT polymerization. Both types of polymerization
require a multifunctional initiator, from which arm growth
occurs. The preparation of 6-arm polystyrene stars by the
RAFT process utilized hexakis(thiobenzoylthiomethyl) ben-
zene (1) as an initiator.[9] The polymerization process is shown
in Scheme 1.[10] The pseudo first-order reaction kinetics and
molecular-weight development were both found to be con-
sistent with a living radical polymerization process. This
RAFT method yielded narrow polydispersity polystyrene
stars with molecular weights of up to 400000, and six arms,
each with a thioester end group. One complication in this
process is the parallel synthesis of a linear chain along with the
star structure (Scheme 1).
A. Pfaltz, Chem. Eur. J. 1997, 3, 887; b) S. Kainz, A. Brinkmann, W.
Leitner, A. Pfaltz, J. Am. Chem. Soc. 1999, 121, 8421.
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Angew. Chem. 1996, 108, 1581; Angew. Chem. Int. Ed. Engl. 1996, 35,
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[8] D. Xiao, Z. Zhang, X. Zhang, Org. Lett. 1999, 1679.
[9] For a review and selected examples of chiral phosphanes with a
ferrocene backbone, see: a) T. Hayashi, M. Kumada, Acc. Chem. Res.
1982, 15, 395; b) Ferrocenes (Eds.: A. Togni, T. Hayashi), VCH,
Weinheim, 1995; c) C. J. Richards, A. J. Locke, Tetrahedron: Asym-
metry 1998, 9, 2377; d) W. Zhang, T. Hirao, I. Ikeda, Tetrahedron Lett.
1996, 37, 4545; e) J. Kang, J. H. Lee, S. H. Ahn, J. S. Choi, Tetrahedron
Lett. 1998, 39, 5523; f) L. Schwink, P. Knochel, Chem. Eur. J. 1998, 4,
950; g) H. Brunner, M. Janura, Synthesis 1998, 45; h) M. T. Reetz,
E. W. Beutternmüller, R. Goddard, M. Pasto, Tetrahedron Lett. 1999,
40, 4977; i) F. Maienza, M. Wörle, P. Steffanut, A. Mezzetti, F.
Spindler, Orgamometallics 1999, 18, 1041; j) U. Nettekoven, P. C. J.
Kamer, P. W. N. M. van Leeuwen, M. Widhalm, A. L. Spek, M. Lutz,
J. Org. Chem. 1999, 64, 3996, and ref. [7].
[10] a) M. J. Burk, M. F. Gross, Tetrahedron Lett. 1994, 35, 9363; b) A.
ATRP/metal-mediated polymerization was also utilized to
synthesize stars. Two different approaches were taken, both
based on the application of sugar initiators. The first approach
we took was based on the work of Haddleton and co-workers
Ã
Marinetti, F. Labrue, J.-P. Genet, Synlett 1999, 12, 1975; c) U. Berens,
M. J. Burk, A. Gerlach, A. W. Hems, Angew. Chem. 2000, 112, 2057;
Angew. Chem. Int. Ed. 2000, 39, 1981.
[11] a) F. Spindler, B. Pugin, H.-U. Blaser, Angew. Chem. 1990, 102, 561;
Angew. Chem. Int. Ed. Engl. 1990, 29, 558; b) Y. Ng, C. Chan, J. A.
Osborn, J. Am. Chem. Soc. 1990, 112, 9400.
[12] F. Spindler, A. Togni, personal communication.
[13] M. D. Fryzuk, P. A. MacNeil, S. J. Rettig, J. Am. Chem. Soc. 1987, 109,
2803.
[*] Prof. T. P. Davis, Dr. M. H. Stenzel-Rosenbaum, Prof. A. G. Fane,
Dr. V. Chen
Centre for Advanced Macromolecular Design
School of Chemical Engineering & Industrial Chemistry
The University of New South Wales (UNSW)
Sydney, NSW 2052 (Australia)
Fax : (61)29385-6250
[**] We acknowledge a DAAD (German Academic Exchange Service)
Scholarship (HSPIII) for Dr. M. H. Stenzel-Rosenbaum.
3428
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Angew. Chem. Int. Ed. 2001, 40, No. 18