Spectrophotometric measurement of swelling of polymer films by very poor solvents

Abstract Solvent swelling of polymers is important for many applications, but can be difficult to measure when thin films or very poor solvents are involved. A novel spectrophotometric method is presented that is well suited for measuring swelling of thick or thin polymer films by very poor solvents. In this method, the solvent is stained with iodine, and solvent uptake is measured by observing the change in visible light absorption of the polymer using a spectrophotometer. Using this method, swelling can be accurately measured in thin (< 2 μm) polymer films and with poor solvents that cause little swelling, even water. Results are presented for PMMA films of varying molecular weights swelled by water, by water–alcohol mixtures, and by undiluted alcohols. Swelling of these films is more rapid and more Fickian than has been reported for bulk samples, probably due to differences in PMMA molecular weight and processing. The properties of the iodine–PMMA complex are also explored. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1082–1089, 2005