Practical strategy to realistically measure the swelling ratio of poly(dimethylsiloxane) without underestimation due to the solvent volatility

We present an experimental method for measuring "realistically" the swelling ratio in terms of weight (SRw) of PDMS, where "realistically" means without the underestimation involved by the standard protocol (weight-measurements in open environment with time-delay incompatible with fast solvent evaporation rate). Comparison with the literature demonstrates that misleading conclusions can result under application of the standard protocol to very volatile solvents. To discuss this point, we develop a mathematical expression of SRw including solvent properties and the effective amount of sorbed solvent determining a weight gain, consider two solvents with different volatility that severely swell PDMS (i.e., toluene and dichloromethane), check that the results of our measurements are consistent with theoretical predictions, demonstrate that our protocol rules out any dependence of SRw on the solvent volatility and its reliability to measure and compare SRw values of PDMS (or any swelling polymer/soft material) in the case of solvents with very different volatility. (C) 2017 Elsevier Ltd. All rights reserved.