Effect of Chemical and Physical Modifications on the Wettability of Polydimethylsiloxane Surfaces

The importance of understanding factors that contribute to surface wettability is highlighted in this new organic chemistry laboratory experiment, which aims to introduce the application of organic chemistry at the interface of polymer chemistry and material science. Polydimethylsiloxane (PDMS), a hydrophobic silicon-based rubber, is polymerized and molded onto templates of varying roughnesses and textures to introduce topology that changes surface hydrophilicity. The topological changes are assessed through optical microscopy imaging, and the wettability is analyzed by measuring the contact angle using an inexpensive digital camera. The molds are treated with boiling water which generates hydroxyl groups on the surface. Successful chemical modification of the polymer surface is confirmed using attenuated total reflection infrared (ATR-IR) analysis, and wettability is assessed through contact angle measurement. Postlab questions focus on the wettability of the physically and chemically modified surfaces and their potential use as scaffolding for tissue engineering. This adaptable experiment is designed to reinforce concepts such as intermolecular forces, introduce polymer structure and synthesis, showcase polymer applications in biological research, and provide an introduction to surface wettability in a visually interesting manner.