Logarithmic Expansion of Swellable Organosilica Material

Swellable organically modified silica (SOMS) is a matrix of crosslinked polysilsesquioxanes that undergoes rapid reversible swelling upon contact with organic solvents. This material has applications in environmental remediation, catalysis, and personal care products. We demonstrate that SOMS exhibits a logarithmic stress-strain relationship when it swells. Using a two-piston force sensor, we measured the swelling force exerted by various samples of SOMS when treated with acetone. As the mass of SOMS inside the force-measurement apparatus increases, the force generated by the swelling also increases, up to a maximum value of approximately 180 N at 650 mg of SOMS. However, the rate-of-change of the force generated by SOMS decreases at larger masses, implying that SOMS is dynamic rather than static. A data collapse of two different SOMS samples (Osorb® and Cyclasorb® ) shows that the underlying behavior of SOMS is uniform across sample types.