Polydopamine (PDA) films, formed by oxidative polymerization of dopamine (DA), have a wide variety of applications as they can function as versatile “primers” for further surface modification and attachment. Typically, PDA films are prepared by submerging a substrate of interest in a basic solution containing DA for an extended period of time, utilizing oxygen in air as the oxidant. In this research, we explored using the facile spin casting method to prepare PDA films on native and functionalized silicon wafers. Sodium periodate was chosen as the oxidant because it is stronger than the commonly used oxygen. All the DA solutions were prepared in acidic acetate buffers to avoid the interference from oxidation by native oxygen. The reaction variables include DA concentration, pH, solution aging time, adsorption time, and surface chemistry. PDA coatings were characterized by contact angle goniometry, ellipsometry, and optical and atomic force microscopy. Additionally, (P)DA chemistry in solutions was monitored by dynamic light scattering and UV-Vis spectrophotometry to correlate with the PDA adhered to surfaces. Our results so far indicate that it is important to control reaction kinetics in terms of solution pH and DA concentration in order to produce thick and homogeneous PDA films - small PDA particles are surface adhesive but do not yield thick PDA films while large particles can improve film thickness but do not readily adsorb to surfaces. Adsorption time was optimized to allow for surface adhesion and to minimize solvent evaporation. The importance of substrate chemistry on the spin-cast PDA film thickness and morphology will also be presented.

Dopamine surface adhesion via spin casting

2019 Spring National Meeting

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