PostDoc
Dr. Wiebe M. de Vos
I joined the Polymers at Interfaces group in December 2009 to work on a short industrially sponsored research project. In May 2010 I started on an ESPRC funded Post-Doc project “Understanding the effects of confinement on near-surface soft nanostructures using neutron and X-ray reflection”. A full description of the project is given below.
Before coming to Bristol, I performed my PhD at the Wageningen University in the Netherlands, working under the supervision of Professor Martien Cohen Stuart. My project focused on polymer brushes, their production, their applications and their interaction with particles. For my research I combined experimental techniques such as optical reflectometry and atomic force microscopy with theoretical approaches based on Self Consistent Field Theory. Examples include a study of the adsorption of the protein BSA to a poly(acrylic acid) brush, and a study into the adsorption of SDS micelles to a PEO brush. In addition, I showed that polydispersity in brushes has a large effect on both their structure and their anti-fouling properties. Finally, I developed a new technique to produce very dense polymer brushes by the simple means of adsorption. The technique was named the Zipper Brush approach, due to its inherent reversibility. A copy of my thesis can be found here . A current list of my publications can be found here.
My research interests include:
- Polymers at interfaces: adsorption, structure, polymer brushes, competition with surfactants, polyelectrolyte multilayers.
- Self-consistent field modelling of polymer brushes, adsorption and polymeric structures.
- Reflection techniques such as optical reflectometry, neutron reflection and ellipsometry.
- Polymers and surfactants at the air-water interface: Langmuir-isotherms, Langmuir-Blodgett transfer and drop shape analysis.
Current project: Understanding the effects of confinement on near-surface soft nanostructures using neutron and X-ray reflection.
The forces that act between surfaces are central to the physics of adhesion, lubrication, friction and determine the stability of emulsions and particles suspensions. One of the most powerful ways to control these inter-surface forces is by the adsorption or other attachment of polymers to the interacting interfaces. Applications include ant-fouling coatings, stabilization of particles suspension and anti-friction coatings. However, the functionality of the polymer depends on how it reacts to being compressed between two interfaces.
While many investigations have focused on measuring the forces between polymer coated interfaces only very little work has been done to measure the structure of the polymer layer under compression. We have recently developed setup that combines a surface force type apparatus with neutron reflection. This setup consists of a silicon or quartz block and a flexible membrane (Melinex or Kapton). Inflation of the membrane against the solid surface provides good contact between the interfaces over a large surface area. The compression force is controlled by the pressure used to inflate the membrane. With this setup it is possible to study the effect of compression on the structure of polymer layers, allowing a clear relation of the measured polymer structures to the forces needed for compression. Early experiments with the setup showed promising results but have also brought to light a number of ways in which the cell could be improved. In this project we will continue the development of this setup. In addition we are now starting our investigations on the compression of thin polymer layers such as swollen polymer gels, polymer brushes and polyelectrolyte multilayers.
Contact: wiebe.devos@bristol.ac.uk
