Subject: Question about charged micellar spheres

From: [email-masked] (Tony Schmidt)
Date: Tue, 25 Jul 95 14:40:27 -0400

Dear Dr. Shapiro,

>     Suppose there are two sets of positively-charged spherical micelles
>one "big" and one "small", and these micelles are capable of binding to a
>surface.  It stands to reason that when two such positively-charged micelles
>bind to a surface they will not come right up against one another because
>they will be repulsed by their mutual positively-charged surfaces.  Now, if
>the _density_ of charges on the surface of the spheres is the same (i.e.,
>both the big micelles and the small micelles have the same number of positive
>charges per unit surface area), will two small micelles be able to sit closer
>to one another than two large micelles, i.e., will there be greater repulsive
>forces between two large micelles resulting in their sitting further away
>from one another than between the two smaller micelles?

The answer to your question may not be simple and, perhaps, cannot be found
within the classical Debye-Huckel theory of ionic mixtures. In particular,
more accurate statistical theories point to the conditions at which equally
charged polyions in electrolyte can ATTRACT each other. In that case, 
polyions should be sufficiently large and/or carry low charge. Discussion
of this problem is given in:
A.B. Schmidt, Phys.Rev. 47E, 3276 (1993); Chem.Phys.Lett. 205, 587 (1993).

Tony Schmidt
[email-masked]