Superhydrophobic, i.e., water repellent, materials are important in a number of applications, such as self-cleaning paints, protective coatings, and textiles. Polymer-based materials such as polystyrene are of particular interest because they are cost effective, durable, heat and chemical resistant. We are fabricating superhydrophobic polystyrene membranes with controlled microstructure to determine how microstructure affects the hydrophobicity. Two methods have been explored to fabricate fibrous membranes with tunable microstructure: electrospinning and shear spinning. Using electrospinning of polystyrene/acetone/toluene, fibers were collected on a rotating mandrel to achieve uniaxially aligned fibers. Orthogonal fibers were achieved with layer-by-layer deposition, i.e., rotating the substrate between deposition of each layer. Fiber sizes between 6 µm and 30 µm by varying the polymer concentration used for electrospinning and fiber spacings from 67.2 µm to 623 µm were achieved. However, electrospinning involves inherently random fiber deposition and the variation in fiber spacing was over 70% relative standard deviation. To improve the uniformity of fiber spacing, we are currently exploring a shear spinning technique known as Spinneret Based Tunable Engineered Parameters (STEP). In STEP, a polymer solution is extruded through a needle and a rotating collector is brought in contact with the liquid droplet; the shear forces overcomes surface tension and pulls the droplet into fibers. Since STEP is a mechanical drawing method, it avoids the whipping instability inherent to electrospinning and greater fiber spacing uniformity is expected. Using STEP, the nanofiber diameters are comparable to electrospinning. The fiber spacing distribution is currently being investigated. To assess the effect of fiber spacing on membrane hydrophobicity, the apparent water contact angle will be measured.

Synthesis and characterization of superhydrophobic fibrous membranes

254th National Meeting (2017)

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