Research Overview

Research in the group is highly interdisciplinary and combines polymer synthesis, soft-lithography, microfabrication, optoelectronic devices and physical aspects of polymer science. Broadly speaking, the research is organized into three main projects:

1.    Polymer Brushes
Polymer brushes are thin films of polymer chains tethered at one end to the surface. In good solvents, sufficiently densely packed chains are forced to stretch away from the surface. This stretching is entropically unfavourable and leads to more or less aligned polymer chains with a tendency to coil back to the surface upon diminishing the repulsive interactions. We are interested in exploiting polymer brushes in responsive surfaces where properties such as wetting, roughness and stiffness can all be switched using external triggers such as pH, temperature, light or salt concentration. Polyelectrolyte brushes provide a particularly versatile (and synthetically challenging) platform, as the mobile counterions in such brushes can be exchanged for a wide range of different salts, thereby imparting a whole range of new properties. One particularly interesting development is the use of polyelectrolyte brushes in nanoactuators, and we recently demonstrated the bending of cantilevers by harvesting the repulsive interactions that lead to surface stresses. We are currently extending the actuation properties of these brushes to explore, in collaboration with Prof. Ulli Steiner in the Cavendish laboratory, the possibility of fabrication molecular 'conveyor belts'.



Recent publications:
Tunable Wettability by Clicking Counterions into Polyelectrolyte Brushes
O. Azzaroni, A. A. Brown, W. T. S. Huck
Adv. Mater. 2007 , 19, 151-154

Multicomponent Polymer Brushes
F. Zhou, Z. Zheng, B. Yu, W. Liu, W. T. S. Huck
J. Am. Chem. Soc. 2006 , 128, 16253-16258

Mechanically-Induced Generation of Counterions Inside SurfaceÐGrafted Charged Macromolecular Films:
Towards Enhanced Mechanotransduction in Artificial Systems
O. Azzaroni, B. Trappmann, P. van Rijn, F. Zhou, B. Kong, W. T. S. Huck
Angew. Chem. Int. Ed. 2006, 45, 7440-7443.

2.   Nanostructured polymers for optoelectronic devices
Polymeric (opto) electronic devices (LEDs, FETs and photovoltaic devices) have attracted enormous commercial and scientific interest because of their potential application in low cost, flexible electronics. Despite considerable progress in the understanding of the fundamental physical processes involved, it is becoming increasingly clear that nanoscale control over the morphology and polymer-polymer interfaces in such devices is of extreme importance to enhance the properties of these devices and make them competitive with silicon based electronics. Unfortunately, most polymeric materials are inherently disordered at the nanometer scale and do not present a molecularly ordered surface chemistry. Our research aims to control the morphology and interfacial structures using polymer brushes, nanoimprint lithography and (block copolymer) self-assembly. The devices are all fabricated in collaboration with the groups of Prof. Richard Friend and Prof. Henning Sirringhaus in the Cavendish laboratory.



Recent publications:
Uniaxial Alignment of Liquid-Crystalline Conjugated Polymers by Nanoconfinement
Z. Zheng, K.-H. Yim, M.S.M. Saifullah, M.E.Welland, R.H. Friend, J.-S. Kim, W.T.S. Huck
Nano Letters 2007, 7, 987-992

Enhancement of Charge-Transport Characteristics in Polymeric Films Using Polymer Brushes
G. L. Whiting, H. J. Snaith, S. Khodabakhsh, J. W. Andreasen, D. W. Breiby, M. M. Nielsen, N. C. Greenham, R. H. Friend and W. T. S. Huck
Nano Letters 2006, 6, 573-578

Dewetting of conducting polymer inkjet droplets on patterned surfaces
J. Z. Wang, Z. H. Zheng, H-W. Li, W. T. S. Huck and H. Sirringhaus
Nature Materials 2004, 3, 171-176

3.   Microdroplets in microfluidics
The central concept is to carry out experiments in small water droplets, separated from each other by a continuous oil phase, within a microfluidic channel. The selection of the catalytically active enzymes is entirely on chip, using molecular biology to generate the new catalysts and analytical chemistry to screen them. The power of the discovery platform is such that it should be able to screen catalysts at rates up to 105 times faster than is presently possible. Combining the attributes of compartmentalisation of reactions into microdroplets with the rapid advances occurring in microfluidics offers the prospect of a completely new approach to experimental science. This requires the development of devices for the generation and manipulation of droplets, and new analytical approaches to follow what is happening, on a very small scale, inside the droplets. This will be achieved by integrating developments in physics, microfabrication, microfluidics, and colloid science.



Recent publications:
From Microdroplets to Microfluidics: Selective Emulsion Separation in Microfluidic Devices
L. M. Fidalgo, G. Whyte, D. Bratton, C. F. Kaminski, C. Abell, W. T. S. Huck
Angew. Chem. Int. Ed. Engl. 2008, in press

A Self-Assembly Approach to Chemical Micropatterning of Poly(dimethylsiloxane)
M. L. van Poll, F. Zhou, M. Ramstedt, L. Hu, W. T. S. Huck
Angew. Chem. Int. Ed. Engl. 2007, 46, 6634-6637.

Surface-Induced Droplet Fusion in Microfluidic Devices
L.M. Fidalgo, C. Abell, W.T.S. Huck
Lab Chip 2007, 7, 984-986