The deposition of functional particle coatings can be achieved in simple and efficient ways by controlled drying of films from liquid suspensions. The particles are organized by combination of convective transport and capillary forces at the liquid/air interface. However, the making of particle coatings is facing two groups of crucial problems. The first challenge is to achieve efficient control over the coating thickness and uniformity. The second problem is the weak adhesion of the particles to the substrate. We will discuss how the first of these key problems could be resolved by understanding and controlling of the process fundamentals, while the second problem can be solved by developing new types of polymer particles with ultrahigh adhesivity. First, we will show how the process of convective assembly can be engineered to rapidly deposit structured coatings at high particle volume fractions. The technique made possible the deposition of colloidal crystals, metallic nanoparticle films, SERS sensor substrates, antireflective coatings, and films of organized biomolecules and live cells. On a side note, we will discuss the process of evaporative assembly of supraparticles in sessile suspension droplets on superhydrophobic surfaces. In the second part of the talk we will discuss the properties of coatings from a new class of ultra-adhesive dendrimeric polymer particles (DPPs). The DPPs are made by scalable processes of antisolvent-induced biphasic precipitation under shear. They are hierarchically structured and thus have a big branched corona of nanofibers. In biomimetic similarity to gecko lizards’ setae, the nanofiber coronas endows the DPPs with extraordinary strong cohesion and adhesion. The strong adhesion was correlated to the contact splitting and van der Waals interactions in the nanofibrous structures. This new class of "gecko leg" polymeric particles can be used to make highly adhesive coatings and nonwovens with exceptionally strong superhydrophilic, superhydrophobic and icephobic capabilities.

Engineering of functional coatings from polymer particles: From ordered microspheres to "gecko leg" morphology

256th National Meeting (2018)

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