Physicochemical and antifungal properties of waterborne polymer nanoparticles synthesized with caffeine

In this work, caffeine was used as a natural additive in the emulsion polymerization of methyl methacrylate with cetyltrimethylammonium bromide (CTAB) or sodium dodecyl sulfate (SDS). Mean particle size and ζ-potential of the particles, glass transition temperature, and molecular weight of polymer chains were not affected by caffeine. However, caffeine improved considerably the colloidal stability of polymer dispersions at ionic strength of 1.0 mol L −1 NaCl. Fourier transform infrared vibrational spectra in the attenuated total reflectance mode (FTIR-ATR) of PMMA synthesized with CTAB or SDS in the presence of caffeine showed shifts of caffeine bands assigned to isolated and conjugated carbonyl groups to higher wavenumbers, indicating favorable interactions. Density functional theory (DFT) calculations revealed interactions between the negatively charged sulfate and the caffeine imidazole ring and between positively charged ammonium group and the isolated carbonyl of the caffeine. Such interactions are responsible for the improved colloidal stability of polymer dispersions synthesized with caffeine. Cell viability assays showed that adding caffeine at 26 × 10 −3 mol L −1 in the polymerization reaction is enough to prevent C. albicans growth in waterborne polymer dispersions.