Rapid gel-like latex film formation through controlled ionic coacervation of latex polymer particles containing strong cationic and protonated weak acid functionalities.

We introduce a controlled ionic coacervation (CIC) process that rapidly forms uniform, gel-like latex films with significant mechanical integrity without loss of water from the film. This process uses latex particles that contain both strong cationic charges and weak protonated acid groups. An increase in pH ionizes the weak acid and triggers the rapid setting of the latex films. The necessary increase in pH can be achieved by coating the latex onto an alkaline surface (such as concrete) or by controlled release of a fugitive acid (such as carbon dioxide). We explore the effect of latex composition and concentration on this process. We show that the CIC process does not require a water-soluble polymer to obtain the rapid-set film properties. Our proposed mechanism for CIC process is consistent with models for rapid, irreversible, particle-particle aggregation.

Contact angle hysteresis, adhesion, and marine biofouling.

Adhesive and marine biofouling release properties of coatings containing surface-oriented perfluoroalkyl groups were investigated. These coatings were prepared by cross-linking a copolymer of 1H,1H,2H,2H-heptadecafluorodecyl acrylate and acrylic acid with a copolymer of poly(2-isopropenyl-2-oxazoline) and methyl methacrylate at different molar ratios. The relationships between contact angle, contact angle hysteresis, adhesion, and marine biofouling were studied. Adhesion was determined by peel tests using pressure-sensitive adhesives. The chemical nature of the surfaces was studied by using X-ray photoelectron spectroscopy. Resistance to marine biofouling of an optimized coating was studied by immersion in seawater and compared to previous, less optimized coatings. The adhesive release properties of the coatings did not correlate well with the surface energies of the coatings estimated from the static and advancing contact angles nor with the amount of fluorine present on the surface. The adhesive properties of the surfaces, however, show a correlation with water receding contact angles and contact angle hysteresis (or wetting hysteresis) resulting from surface penetration and surface reconstruction. Coatings having the best release properties had both the highest cross-link density and the lowest contact angle hysteresis. An optimized coating exhibited unprecedented resistance to marine biofouling. Water contact angle hysteresis appears to correlate with marine biofouling resistance.