 |
Manny's Project Page - CAMP Summer 2007 |
 |
Intern: Manuel Galan, Chemical Engineering
Mentor: Robert Farina
Faculty Supervisor: Matthew Tirrell
Department: Chemical Engineering |
MODELING OF POLYELECTROLYTE BRUSHES IN VARIOUS IONIC ENVIRONMENTS
Polyelectrolytes are polymers with repeating charged monomer segments.
Polyelectrolytes are used in biological applications such as in coating the
surfaces of artificial joints and also in commercial applications which include
shampoo and skin care products. Understanding polyelectrolyte behavior is
essential to the improvement of these applications. The polyelectrolytes we
study are composed of a hydrophobic neutral block and a hydrophilic
polyelectrolyte block which contains negatively charged segments. In an aqueous
solution with a hydrophobic surface present, polyelectrolytes tether to the
surface by anchoring themselves with the hydrophobic block. The hydrophilic
tails extend into the solution forming what are called “polyelectrolyte
brushes”. Depending on the salt concentration in the solution surrounding the
polyelectrolyte brush, we determine the brush to be functioning in either an
osmotic or a salted brush regime. An osmotic brush regime occurs when there are
a greater number of counterions inside the brush than the concentration of salt
in the solution. The salted brush regime has a greater external salt
concentration than the concentration of counterions inside the brush. The
purpose of this work is to model these brushes according to force balance and
thermodynamic equations. With these equations, the forces of interaction
between polyelectrolytes in different salt concentrations will be calculated.
These models will be compared to future experimental results using a Surface
Forces Apparatus (SFA). Gaining a greater understanding of these brushes can
lead to new ideas and breakthroughs both commercially and biologically.
Return to the CAMP 2007 project list
