Seminar by Olli Ikkala

Supramolecular concepts combined with synthetic block copolymers allow self-assembled hierarchies and macromolecular engineering to tune the properties.(1-2) Here we address some recent approaches to extend the concepts towards biological and bioinspired materials.

Previously it has been shown that star-shaped synthetic block copolymers allow Archimedean tiling-type self-assemblies.(3) Here we discuss our first results on star-shaped macromolecules that have both polypeptidic and synthetic blocks, which show related hierarchical self-assemblies.(4) Previously, polypeptide-surfactant complexes are shown to allow self-assemblies and control of conformation.(5-8) By incorporating supramolecular approaches, hierarchies are here discussed by complexing block-like lipids to homopolypeptides.(9) Recently we (Walther et al) showed that nacre-mimetic mechanically strong materials could be achieved by facile lamellar self-assemblies between nanoclay and polyvinyl alcohol, followed by chemical cross-linking of the polymer.(10) This allowed for the first time methods to prepare nacre-mimetic materials using processes that can be scaled towards large-scale production. Here we describe a more recent method, where the connectivity of the polymers between the layered nanoclays is controlled using supramolecular ionic concepts.(11) Finally, we emphasize the importance of native cellulose nanofibers as constructional units for bioinspired materials. The nanofibers are expected to have excellent mechanical properties, which we exploit to show the first ductile and deformable aerogels.(12) Such materials are useful templates for nanoscale engineering. The various shown routes pave ways for biomimetic engineering using biological and synthetic tectons of different sizes, according to the general scenario suggested already early(1-2).

1.   O. Ikkala and G. ten Brinke, Science, 295, 2407 (2002).
2.   O. Ikkala and G. ten Brinke, Chem. Comm., 2131-2137 (2004).
3.    Y. Matsushita, Polymer, 50, 2191 (2009).
4.    S. Junnila, S. Hanski, H. Iatrou, N. Hadjichristidis, N. Houbenov, O. Ikkala, to be submitted.
5.    W. McKnight, E. Ponomerenko, D. Tirrell, Acc. Chem. Res. 31, 781 (1998).
6.    S. Hanski, S. Junnila, L. Almásy, J. Ruokolainen, Olli Ikkala, Macromolecules, 41, 866 (2008).
7.    R. Ramani, S. Hanski, A. Laiho, R. Tuma, S. Kilpeläinen, F. Tuomisto, J. Ruokolainen,  O. Ikkala, Biomacromolecules, 9, 1390 (2008).
8.    S. Junnila, S. Hanski, R. J. Oakley, S. Nummelin, J. Ruokolainen, C. F. J. Faul, O. Ikkala, Biomacromolecules, 10, 2787 (2009).
9.   S. Hanski, S. Junnila, A. J. Soininen, J. Ruokolainen, O. Ikkala, submitted
10.  A. Walther, I. Bjurhager, J.-M. Malho, J. Ruokolainen, J. Pere,  L. Berglund, O. Ikkala, Nano Letters, asap, (2010).
11.  A. Walther, I. Bjurhager, J.-M. Malho, J. Ruokolainen, L. Berglund and O. Ikkala, submitted.
12.   M. Pääkkö, R. Silvennoinen, J. Vapaavuori, A. Nykänen, M. Ankerfors, H. Kosonen, J. Ruokolainen, T. Lindström, L. A. Berglund, and O. Ikkala, Soft Matter, 4, 2492 (2008).