Many coatings only need to either be durable or fast drying, usually sacrificing long term stability in favor of quick setting, or vice versa. One coating type that cannot afford to sacrifice either performance feature is traffic paint. These paints are made up of a weak polycation, an anionic latex, and a volatile base which evaporates upon application. The high pH in the initial formulation deprotonates the polycation, rendering it charge neutral. However, upon evaporation, the resulting drop in pH allows for the electrostatic complexation between the polycation and the latex. The electrostatic interactions used in these formulations parallels that of complex coacervation, an associative liquid-liquid phase separation. In this thesis, we will take advantage of model coacervate systems to elucidate the design parameters necessary for the formulations to serve as paints.
We used a series of simplified systems, starting with a system consisting of a weakly cationic homopolymer and weakly anionic homopolymer before moving on to anionic copolymers with decreasing charge density, and ultimately an anionic latex. We investigated the effects of pH, charge stoichiometry, and salt concentration for each of these systems, using turbidimetry and optical microscopy as a means of measuring the extent of coacervation. We determined that, the removal of 99.9% of the charge on our polymers was necessary for coacervation to no longer occur. This can be achieved using either salt or pH, however, salt may be preferable, due to the inherent hazardous properties of highly acidic or basic solutions. Very excitingly, we were able to observe coacervation with latex particles. To our knowledge, there are no known observations of polymer-particle coacervation prior to this study.
These results suggest that the underlying physics and design principles associated with fast setting paints can be explored using complex coacervation, and that a much broader range of parameters can be used to control the setting of these materials, beyond just pH used in existing technology. Future efforts are still needed to better understand the effect that polymer chemistry has on the complexation of these materials, and how it also affects the mechanical and adhesive properties of coating produced by such formulations.
| Identifer | oai:union.ndltd.org:UMASS/oai:scholarworks.umass.edu:masters_theses_2-2102 |
| Date | 01 July 2021 |
| Creators | Bryant, Nicholas |
| Publisher | ScholarWorks@UMass Amherst |
| Source Sets | University of Massachusetts, Amherst |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Masters Theses |
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