End-tethered polyelectrolyte brushes have been a major area of research in the Tirrell group during recent history.  Polyelectrolyte brushes, block copolymers with one polyelectrolyte block and one hydrophobic block, are found both in nature (e.g., surfaces of cartilage and mammalian lung interiors) and in commercial products (e.g., shampoo, skin care, and surfaces of medical devices).  Because their uses are so vast, it is considered important to understand both their behavior and the forces of interactions between them.  This is done by first tethering two separate polyelectrolyte brush layers to two separate hydrophobic surfactant layers.  Using the Surface Forces Apparatus (SFA) the two polyelectrolyte brush layers are then brought together and separated several times while in an ionic solution.  This gives us information on how polyelectrolyte brushes repel and attract to themselves and also how their brush heights vary in different solutions. 

Polyelectrolyte brushes respond very differently depending upon the ions used in solution.  The group has done extensive research using the SFA to study polyelectrolyte brushes in mono-valent ionic solutions; mostly using Na+.  This work has led to curiosity about multi-valent ions in solution.  While studies have also been done using the di-valent Ca2+ and the tri-valent Al3+ ions, there is still much more that needs to be learned in these areas.  My work will consist of studies of various mono and multi-valent salt solutions.  We plan on using a variety of different salt solutions.  Physiologically there are both mono and multi-valent salts in the body which make our future studies extremely important for biological applications.