[Prev][Next][Index][Thread]
Re: WSN: salting out, deionized H2O,.. (from P.Wiggins)
From: Philippa Wiggins <p.wiggins@auckland.ac.nz>
-------------------------------------------------------------------------------
I find in my experiments with polymers in aqueous systems that water
associated with the polymers exists in two states of different
density and different solvent properties. High density water appears
to be highly reactive, while low density water is relatively inert.
Both the amounts of these water populations and their properties are
sensitive to even low concentrations of solutes; eg. 0.1 mM MgCl2 or
CaCl2 or even NaCl have substantial effects. Moreover the effects of
the ions differ: some stabilise low density water and some stabilise
high density water. Other solutes have mixed effects. These effects
are all non-linear so that it is not possible to extrapolate from
experiments I have done down to the very small concentrations that
you are interested in. I found, however, with the 0.1 mM
concentrations that I have used that low density water was stabilised
to a remarkable degree compared with no added ions at all. Higher
concentrations were less effective. I do not, of course, know the
answer to your problem, but I wonder whether changes in the
reactivity of water associated directly with your polymers might not
hydrolyse bonds etc.
Good luck
Philippa Wiggins