Nature has developed elegant and economical strategies to produce materials with exquisite structure control to accomplish specific properties. The use of these concepts to synthesize and/or process materials (biomimetics) is an active research field of materials science. In our research group, we combine expertise in polymer synthesis, structure format ion and bioadhesion. We aim to use biologically inspired strategies to develop polymeric materials for next generation adhesives and functional materials. Currently, the group is mainly working on three research areas:
(1) Reversible Anti-Fouling Polymer Coatings
Fouling and fouling control are major challenges in a wide variety of applications, ranging from biomedical devices to membrane technology. Fouling of surfaces leads to an increase in energy consumption, together with an increase in operational and maintenance costs to keep these devices running. Currently used cleaning methods, which remove these fouling agents, are often incomplete and their harsh conditions may damage the system of interest. Coating the system with a dense layer of end-grafted polymer, a polymer brush, has proven to reduce the fouling behaviour, but their long-term stability is poor. Hence, irrespective of the cleaning or anti-fouling strategy employed, all surfaces will eventually become fouled.
We aim to develop reversible anti-fouling polymer coatings via a cheap and simple adsorption method. Moreover, if the polymer coating gets fouled or damaged, the coating can easily be removed and reapplied. This is expected to lead to a new generation of anti-fouling coatings that can easily be applied on large surfaces, and that can be easily regenerated when needed.
(2) Complex Coacervate-Based Adhesives
Sea creatures like mussels and sandcastle worms are able to anchor themselves underwater onto rocks (mussels) or glue sand grains together (sandcastle worms). One of the mechanisms that enables the strong underwater adhesion is the mixing of oppositely charged polyelectrolytes. The resulting dense liquid polymer phase is called a complex coacervate. Based on this principle we aim to develop an adhesive that works in a wet environment. Due to the introduction of thermoresponsive crosslinkers a second interaction is possible. This second interaction will enable the material to be more durable, firmer and stronger. These adhesives can have applications in, for example, healing of deep tissue wounds.
In this project we focus on the architecture and the mechanical behaviour of the complex coacervates and the effect of environmental changes, such as pH, salt, and temperature. Besides experiments we will use molecular dynamics simulations to predict the behaviour of the polyelectrolyte complex coacervate for a better guide to the design of polyelectrolytes.
(3) Well-defined hydrophobic/strong polyelectrolyte block copolymers for enhanced underwater adhesives
Strong polyelectrolytes are polymers that are formed through polymerization of charged monomers, with the presence of these charges being independent of the pH and temperature. In other words, and unlike weak polyelectrolytes, the charge density of these polymeric materials is insensitive to the environment. Block copolymers that combine such strong polyelectrolytes with hydrophobic features are therefore highly interesting for use in underwater adhesives (Adv. Mater., 2018, 30, 1704640). However, due to their amphiphilic nature, the synthesis, characterization and processing of such polymers remains a challenging task, and is likely even impossible.
To this end, in this research project new polymeric materials will be developed that are based on protected strong electrolytes and hydrophobic monomers, resulting in well-defined and fully hydrophobic block copolymers that can be synthesized, characterized and processed by the conventional methods. Subsequently, an external stimulus (either thermal or chemical) will transform the hydrophobic material into the desired ionic-hydrophobic block copolymer (See Figure). Before being applied in adhesives, a better understanding of the amphiphilic character is expected to be achieved by studying the self-assembly of these copolymers in bulk and solution, using techniques like light scattering, X-ray diffraction and electron microscopy.
In summary, the research project will involve the following aspects:
- Design and synthesis of new protected monomers;
- Preparation of block copolymers by living and/or controlled polymerization techniques;
- Studying the self-assembly of the deprotected materials in bulk and/or solution;
- Incorporation of the copolymers in polyelectrolyte-containing adhesives.
(4) Complex Coacervate-Based Fibers
Green processing is extremely challenging, because of the low solubility of most polymers in water, especially considering the relatively high polymer concentrations and molecular weights required for spinning. Polyelectrolytes are a clear exception to this rule, but in the absence of salt result in solutions with significantly higher viscosities than neutral polymer solutions. Only in recent years oppositely charged polyelectrolytes were mixed to enable processing: solid polyelectrolytes complexes were processed with extrusion and complex coacervates were processed with electrospinning, without requiring any organic solvents. These approaches demonstrated the processability of polyelectrolyte complexes and electrostatically driven coacervates, but did not exploit alignment or conformational changes to achieve new property profiles. If high performance fibers, with high strength and high stiffness are required, the polymer chains need to be highly extended and aligned. The complex coacervate extrusion approach, proposed here, is thus unique as it combines the processability of polyelectrolytes complexes with their potential high mechanical performance, without requiring any toxic solvents.
|Last modified:||01 October 2019 2.26 p.m.|