It has been established about a decade ago that dopamine (DA) oxidizes, polymerizes, and aggregates readily in solution and deposites onto a variety of substrates to form robust polydopamine (PDA) coatings. The coating process typically involves submerging a substrate of interest in a buffered solution containing dopamine. Recently, we observed self-assembled patterns of PDA films upon drop casting aqueous solution containing DA, sodium periodate (SP) and acetate buffer onto silicon wafer substrates. The formation of the ordered thin films appears to consist of drying-induced self-assembly of component materials (DA, oxidant and buffer salt) in addition to PDA materials. Experiments have been carried out by varying the type of oxidant (SP or oxygen), using solutions containing a subset of the components and dopamine solutions that are aged for a varying amount of time. Optical microscopy is used to study drying dynamics of freshly cast DA solution as well as to image dried films. Dynamic light scattering and transmission electron microscopy are utilized to characterize the PDA particles formed in solution in parallel. The stability of the PDA thin films prepared by self-assembly is assessed by soaking the samples in water under acidic, basic, and neutral conditions. The films are characterized by ellipsometric thickness, dynamic water contact angles, and surface morphology before and after the stability test. The objectives of this research are to elucidate the role of the individual component in the self-assembly and film formation process as well as the integrity of the resultant PDA thin films.

Self-assembled polydopamine coatings via drop casting

255th National Meeting (2018)

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