Friday, February 8, 2013

Some notes on colloids, surfactants, and the Debeye length

In the lab I frequently handle and create colloids--suspensions of one type of material in another, such as solid particles in water. A good reference site I just found for understanding and working with colloids is at SubsTech's website.

Things I also learned today:
  1. The Debeye length may be conceptualized as the characteristic size of a fluctuation of the electrostatic potential inside a solution of charged particles. Longer Debeye lengths mean longer distances for which the potential remains roughly the same.
  2. Surfactants may be used to stabilize a colloidal dispersion. This is different from electrostatic stabilization, whereby some charge is permanently located on/inside the particles to cause them to repel one another.
Unfortunately, I do not yet have a good concept for why surfactants may stabilize a colloid. I suspect that the concept is related to polymeric stabilization.