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

- Swelling ratio of PDMS without underestimation due to solvent volatility.
- Formula of the swelling ratio including solvent properties and sorbed amount.
- Misleading results stemming from the conventional experimental protocol.
- Reliable comparison between solvents with different volatility by our protocol.
- Experimental protocol that can be applied to any polymer swelling in contact with solvents.

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.

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