Inviterte foredrag til 8. Norske Polymer- og kolloidvitenskapelige Vårmøte

Novel Amphiphilic Block Copolymers

Made by Controlled Free Radical Polymerization

André Laschewsky

Universität Potsdam, Institut für Chemie Karl-Liebknecht Str.24-25, 14476 Potsdam-Golm
laschews@rz.uni-potsdam.de
and
Fraunhofer Institut für Angewandte Polymerforschung FhG-IAP , Geiselbergstr.69, 14476 Potsdam-Golm (Germany), laschewsky@iap.fraunhofer.de

Amphiphilic block copolymers are a most intriguing species of amphiphiles.1-6 However, the preparation of such block copolymers had been considered for long to be the "holy grail" of polymer synthesis, as generally, delicate living polymerization methods had been necessary. These methods are mostly cumbersome, very sensitive against impurities, and have only low tolerance to functional groups, in particular to such that are hydrophilic, consequently limiting the synthesis of amphiphilic block copolymers to few systems. This situation changed dramatically with the advent of the methods of controlled free radical polymerization (CFRP) since 2000,7-9 which are much more tolerant of functional groups. This created a booming research field in the past decade, and has made numerous polymers with so far unusual - or even unknown - block structure and of unusual architecture accessible.3, 4

This contribution will first introduce to the strategies, opportunities and difficulties encountered in the synthesis of amphiphilic block copolymers by CRP, in particular by the RAFT (reversible addition fragmentation chain transfer) method. Then, the making of classical polymer architectures will be addressed. Finally, unusually complex block copolymer amphiphiles made accessible by virtue of this technique will be exemplified, highlighting amphiphilic stimulus-sensitive systems, triphilic ternary block copolymers, and dual brush giant surfactants.10-16

Block copolymer

Scheme 1.  Comparison of the architecture of a standard surfactant, a macrosurfactant, and a giant surfactant (from top to bottom). The left (~~~) and the right side (·) represent the hydrophobic and hydrophilic elements, respectively.

References

  1. I. W. Hamley, Block Copolymers in Solution: Fundamentals and Applications. John Wiley & Sons Ltd: Chichester, England, 2005.
  2. S. Garnier; A. Laschewsky; J. Storsberg, Tenside Surf. Det. 2006, 43, 88-102.
  3. J.-F. Lutz, Polym. Int. 2006, 55, 979-993.
  4. A. Blanazs; S. P. Armes; A. J. Ryan, Macromol. Rapid Commun. 2009, 30, 267-277.
  5. M. A. Cohen Stuart, Colloid Polym. Sci. 2008, 286, 855–864.
  6.  I. C. Reynhout; J. J. L. M. Cornelissen; R. J. M. Nolte, Acc. Chem. Res. 2009, 42, 681-692.
  7. K. Matyjaszewski; T. P. Davis, Handbook of Radical Polymerization. John Wiley and Sons, Inc.: Hoboken, 2002.
  8. K. Matyjaszewski; ed., Macromolecular Engineering: Precise Synthesis, Materials Properties, Applications. Wiley-VCH: Weinheim, 2007; Vol. 1.
  9. V. Percec; ed., Chem. Rev., vol.109 (11), thematic issue on: Frontiers in Polymer Synthesis 2009.
  10. M. Arotçaréna; B. Heise; S. Ishaya; A. Laschewsky, J. Am. Chem. Soc. 2002, 124, 3787-3793.
  11. K. Skrabania; J. Kristen; A. Laschewsky; Ö. Akdemir; A. Hoth; J.-F. Lutz, Langmuir 2007, 23, 84-93.
  12. M. Mertoglu; S. Garnier; A. Laschewsky; K. Skrabania; J. Storsberg, Polymer 2005, 46, 7726-7740.
  13. K. Skrabania; H. v. Berlepsch; C. Böttcher; A. Laschewsky, Macromolecules 2010, 43, 271-281.
  14. A. Laschewsky; J.-N. Marsat; K. Skrabania; H. v. Berlepsch; C. Böttcher, Macromol. Chem. Phys. 2010, 211, 215-221.
  15. D. Zehm; A. Laschewsky; M. Gradzielski; S. Prévost; H. Liang; J. P. Rabe; R. Schweins; J. Gummel, Langmuir 2010, 26, in press (doi: 10.1021/la903087p).
  16. A. M. Bivigou-Koumba; E. Görnitz; A. Laschewsky; P. Müller-Buschbaum; C. M. Papadakis, Colloid Polym. Sci. 2010, 288, online first.

Preparation of non-spherical composite nanoparticles

Alex M. van  Herk, Hans Heuts, Syed Imran Ali

Eindhoven University of Technology, The Netherlands


Colloidal nanocomposites are of major interest to improve properties of polymeric films. Many projects focus on incorporation of clay platelets in latex systems. Only few systems actually succeed in encapsulation of clay platelets. In order to use the full potential of incorporation of clay in latex particles the orientation of the clay platelets in the final film should be non-random. This means that the anisotropy of the clay platelet should be expressed also in the shape of the latex particle. So peanut shaped and flat latex particles are desired structures that in principle could lead to maximum usage of the high aspect ratio of the clay platelets. In this presentation the results of successful encapsulation of both natural and synthetic clay is shown, leading to anomalous latex particle shapes that can be used to make polymeric films with desired alignment of the clay platelets.

Modification of the clay in combination with a designed emulsion polymerization process is the key to obtaining the desired results. Growing polymer from the surface by a RAFT approach can lead to uniform layer thickness of the encapsulating polymer and therefore to flat latex particles.
Picture 1 Picture 2
Dumbell or peanut shaped latex particles obtained in a conventional starved emulsion polymerization in the presence of modified montmorrilonite clay platelets [1]. Flat latex particles obtained in a RAFT controlled emulsion polymerization onto synthetic Gibbsite clay platelets [3].


References:
  1. D.J. Voorn, W. Ming, A.M. van Herk, Macromolecules 2006, 39, 4654-4656
  2. A.M. van Herk and A.L. German, "Microencapsulated pigments and fillers", contribution to the book 'Microspheres, Microcapsules & Liposomes', vol 1 : Preparation & Chemical Applications, Citus Books, London , ed Prof. R Arshady (1999).
  3. S.I. Ali, J.P.A. Heuts, B.S. Hawkett, A.M. van Herk, Langmuir 2009, doi:101021/1a9012697

Siden oppdatert 29.1.2010