Fabrication of polymeric surfaces with similar contact angles but dissimilar contact angle hysteresis

This note provides methods to fabricate polymer surfaces which have similar advancing or receding contact angles with distilled water but dissimilar contact angle hysteresis. Poly(methyl methacrylate) (PMMA), Polystyrene, Polypropylene and Teflon AF were chosen, and three different methods namely spin coating, spray coating, and heat press were used in the fabrication. Contact angle measurements were performed using the sessile drop method, and atomic force microscopy was used to measure the roughness of the fabricated surfaces. Surfaces obtained from spin coating, spray coating and heat press showed very different wettability, which can be explained by their different surface roughness or heterogeneity. For spin coating, by changing the spinning rate and concentration of the solution, contact angle hysteresis of the PMMA surface can be changed in the range of 13-25°. For heat press, contact angle hysteresis can be varied from 21° to 29° by changing the plate and/or the method of separating the plate from the surface. For Teflon AF surfaces, the contact angle hysteresis can be varied from 10° to 23° by using different surface fabrication methods. For surfaces made of mixed solution of PMMA and Polystyrene, the ratio of PMMA:Polystyrene was shown to affect the surface wettability, and the results were explained by changes in the pattern and size of the heterogeneous domains on the surface.