Functional Materials Based on Self-Assembly of Comb-Shaped Supramolecules

Summary

During recent years Prof. Olli Ikkala (Helsinki University of Technology) and I developed a method to prepare functional polymeric materials based on self-assembly of comb-shaped supramolecules created by attaching “short” chain molecules (amphiphiles) with physical interactions (e.g. hydrogen bonding) to either a homopolymer or to one of the blocks of a diblock copolymer. One of the most interesting aspects of our approach is the possibility to construct hierarchically structured materials: the presence of structure at different length scales. In the simplest case of a so-called lamellar-within-lamellar structure, the material consists of alternating lamellae (the large length scale) of which every other one is in turn again internally self-organized in the form of alternating lamellae (the short length scale). Many other structures (lamellar-within-cylinders, lamellar-within-spheres, etc) have been constructed as well.

With the present proposal we seek support to continue our research in this area. Four main topics to be addressed concern the extension of the class of hierarchically structured materials, the exploration of macroscopic orientation by external fields, the application of these materials for elastic templates for conducting nanotubes with tunable diameter and the preparation and thermo-mechanical properties of nano-objects.

Project 1. New hierarchical structures. Self-organization of comb-shaped supramolecules based on chiral polymers.
The hierarchically ordered materials involve two length scales. The "short" length scale is introduced by microphase separation between the polar and nonpolar part of the supramolecular comb block. In all but one case the corresponding structure is lamellar. Here we propose to investigate what happens if chiral polymers, such as poly(diphenyl-4-pyridylmethyl methacrylate), are used as homopolymer or as one of the blocks block of a diblock copolymer to serve as the backbone of the supramolecular comb architecture.

Project 2. Macroscopic alignment of hierarchically ordered materials by external fields.
True macroscopic order in hierarchically structured materials poses special problems not present in ordinary diblock copolymers due to a conflict between thermodynamic and kinetic factors. To investigate pathways towards macroscale order in such systems we recently completed a rheometer that allows in-situ X-ray studies of shear-induced alignment. For the first time it is possible to study the process as a function of temperature and shear parameters in-situ not only tangentially (well known) but also radially. Besides mechanical fields most appropriate for bulk samples, we also propose to address surface directed alignment and electric field alignment of thin films. Here the supramolecular nature of the constituents presents special problems.

Project 3a. Elastic membranes as templates for conducting nanofibers with tunable diameter.
Our approach allows a facile way of preparing membranes with hexagonally ordered "empty" cylinders. After cross-linking, a stretchable nanoporous template may be obtained, where biaxial stretching gives relatively large nanopores to which appropriate monomers and chemical oxidizing agents can be added. Subsequent partial stress relief results in a porous membrane with cylindrical pores of a controlled diameter and filled with the appropriate solution. After polymerization conducting polymer fibres confined to nanocylinders of a controlled diameter are obtained.

Project 3b. Thermo-mechanical properties of core-corona nano-objects
The preparation of core-corona nanorods is very similar to that of membranes. We propose to study the mechanical properties of such nano-objects as a function of temperature using atomic force microscopy. To this end nanorods are dispersed on a suitable membrane thereby crossing pores. Given the dramatic effect of film thickness on glass transition temperatures of thin films, the influence of the dimensions of both the core and the corona on the elastic modulus is of special interest.

Products

Scientific article

  • O. Ikkala, G.O.R. Alberda van Ekenstein, W. van Zoelen, E Polushkin(2005): Nanorod Engineering by Reinforcing Hexagonally Self-Assembled PS-b-P4VP(DDP) with PPE Soft Matter pp. 280 - 283
  • W van Zoelen, G.O.R Alberda van Ekenstein, O Ikkala, G ten Brinke(2006): Incorporation of PPE in Lamellar Self-Assembled PS-b-P4VP(PDP) Supramolecules and PS-b-P4VP Diblock Copolymers Macromolecules pp. 6574 - 6579
  • G Gobius du Sart, R Rachmawati, V Voet, G.O.R Alberda van Ekenstein, E Polushkin, G ten Brinke, K Loos(2008): Poly(tert-butyl methacrylate-b-styrene-b-4-vinylpyridine) Triblock Copolymers: Synthesis, Interactions, and Self-Assembly. Macromolecules pp. 6393 - 6399

Thesis

  • W. van Zoelen(2009): PS-b-bP4VP(PDP) Comb-Shaped Supramolecules , GRONINGEN  March 13, 2009
  • G. G. du Sart(2009): Supramolecular Triblock Copolymer Complexes , GRONINGEN  May 1, 2009

Details

Project number

700.52.305

Main applicant

Prof. dr. G. ten Brinke

Affiliated with

Rijksuniversiteit Groningen, Faculteit Wiskunde en Natuurwetenschappen, Polymeerchemie

Team members

Dr. S. Bondzic, Dr. R.J. Nap, Dr. G. G. du Sart, Dr. N. Sushko, Dr. W. van Zoelen

Duration

15/10/2003 to 02/11/2010