Environmentally Compliant Fluoro-Containing MMA/nBA Colloidal Dispersions; Synthesis, Molecular Modeling, and Coalescence
Originally published in Macromolecules, 2009, 42, 7828–7835
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While aqueous phase colloidal synthesis of F-containing dispersions is often restricted by low solubility and surface tension of monomers, the use of bioactive dispersing agents, such as phospholipids, may alleviate these problems. Using 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC), we copolymerized heptafluorobutyl methacrylate (FBMA), heptafluorobutyl acrylate (FBA), heptadecafluorodecyl methacrylate (FMA), heptadecafluorodecyl acrylate (FA) with methyl methacrylate (MMA) and n-butyl acrylate (nBA) monomers which resulted in the formation of stable nonspherical colloidal dispersions that contain up to 15% (w/w) of the fluoropolymer (FP) phase. These studies report for the first time an aqueous phase FP colloidal dispersion synthesis without the use of fluoro-dispersing agents. Experimentally determined by transmission electron microscopy (TEM) particle phase-separated morphologies consist of the FP phase that polymerize on the surface of p-MMA/nBA core particles. Thermodynamic molecular modeling simulations show that the coexistence of fluorinated and nonfluorinated segments is energetically favorable and the presence of the FP phase decreases the cohesive energy density of macromolecular chains. These theoretical predictions are in agreement with the experimental results. Nonspherical FP containing colloidal particles coalesce to form stable films with ultra low static and kinetic coefficients of friction as well as the low surface energy which result from stratification of the FP phase near the film-air (F-A) interface. As a result, property gradients are achieved, which are manifested by the low static and kinetic coefficients of friction near theF-Ainterface due to the presence of the FP phase and lower glass transition temperature (Tg) of p-MMA/nBA phase near the film-substrate (F-S) interface. The latter facilitates the flow during coalescence.