Polymer brushes for nano-devices, bio-technologies, adhesion and ...

Polymer brushes for nano-devices, bio-technologies, adhesion and friction Mini-colloquium (12) Fabien LEONFORTE

Lionel BUREAU

Instit¨ ut f¨ ur Theoretische Physik Georg-August-Universit¨at, Friedrich-Hund-Platz 1 D-37077 G¨ottingen Germany [email protected]

Laboratoire Interdisciplinaire de Physique (LIPhy) UMR5588 CNRS-UJF, 140 rue de la Physique F-38402 St Martin d’Heres France [email protected]

Keywords: Numerical modelisation; nano-scale experimental approaches; nano-structuration; Soft Matter and complex macromolecular systems; polymers and bio-polymers. Development and processing of functional materials is one of the main issue in micro- or nanotechnologies. A growing number of technological applications are in need of e.g. adhesives that could stick on every type of surfaces, super-hydrophobic, anti-friction or anti-fouling coatings, or adaptive materials that could respond to some variations induced in their environment. Because of their versatility as surface coatings as well as their ability to provide experimental and theoretical models, polymer brushes have been widely used in order to address problems like fine tuning of interactions between surfaces [1], reversible tuning of adhesion and wetting [2, 3, 4], or control of the motion of nano-objects [5]. They can also be fabricated on the nano and macroscale for electronics [6] and microfluidic devices [7]. Furthermore, new experimental grafting from techniques have allowed to turn inorganic surfaces to organic, biologically friendly ones that provide broad release, selectivity and attachment capabilities, including under the control of an external stimulus. Such functionalization of stimuli-responsive brushes, like multi-component pH- and thermo-responsive mixed brushes (see Fig. 1 for example), is therefore extremely relevant for biological purpose like control release of drug delivery. Despite their apparent simplicity, the properties of functionalized and adaptive polymer brushes are difficult to address theoretically and experimentally (e.g. due to their use in in-situ applications, or because of the coupled constraints induced by the nanoscale, the changing environment and the induced response of the material). Their promising applications thus necessitate to capture the relevant parameters that can alter their stimulated response to environmental modifications, as well as to anticipate and optimize the architecture of the adaptive materials in relation to the used stimuli (electric field, solvent, temperature, salinity, magnetic field, optical triggering...). Therefore, a detailed understanding of such systems is critically dependent on the bi-directional passing of relevant and pertinent parameters between experiment, theory and modeling. The aim of the Mini-colloquium is precisely to favor such an exchange by gathering researchers from various fields (nano-fluidics, membranes, biophysics...) working with polymer brushes. We plan to address three main topics: (i) multi-component pH- and thermo-responsive brushes : properties and applications, (ii) self-organization of nano-objects in contact with functionalized and responsive polymer brushes, (iii) nano-fluidics for biology and bio-engineering and adaptation to friction. Experimentalist or theoreticist, you are welcome to propose an oral contribution or a poster if your studies deal with the aforementioned topics.

Figure 1: Side and top views of a thermo-responsive multi-component poly(acrylic acid)-b-poly(Nisopropylacrylamide)/poly(ethylene oxide) brush in water. The grafted densities are ρg = 0.16 nm−2 for the diblock and ρg = 0.48 nm−2 for the PEO components of the brush. The last row depicts the density profile ρα (z) of each components α as a function of the distance z to the grafted substrate. Results obtained using SCMF [8] simulations.

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