Eur. Phys. J. E (2016) 39: 99
https://doi.org/10.1140/epje/i2016-16099-0

Tips and Tricks

Measuring the solubility of solids in non-solvents: case of polystyrene in alkanes

¹ Department of Physics & Astronomy, University of Waterloo, 200 University Ave. W., Waterloo, N2L 3G1, Ontario, Canada
² Perimeter Institute for Theoretical physics, 31 Caroline St. N. Waterloo, N2L 2Y5, Ontario, Canada

^* e-mail: jforrest@uwaterloo.ca

Received: 18 March 2016
Accepted: 20 September 2016
Published online: 23 October 2016

Abstract

We introduce a simple and sensitive technique for measuring extremely low solubilities with a small sample size and small solvent volume. This technique involves measuring the decrease in the thickness of a supported thin film after exposure to a drop of known volume of solvent and removal of the solution. The feasibility of measuring very small changes in film thickness directly translates to the ability to measure extremely low solubility while at the same time using only μL of solvent. We apply the technique to the case of polystyrene with M_w values in the range 2500 g/mol to 22200 g/mol in alkane solvents and show that we can easily measure a solubility of 0.1 g/L using only 1 g of material and 3 L of solvent for each sample.