Microcapsules with compact wall from hydrocarbon/fluorocarbon composite surfactants for electrophoretic display

The components and their concentration ratio of surfactant mixture in aqueous solution of gelatin and sodium carboxymethylcellulose (NaCMC) are very important during the preparation of stable microcapsules for electrophoretic display. In this work, hydrocarbon/fluorocarbon composite surfactant was introduced for the first time into the capsule wall to improve the chemical resistance and barrier property of the microcapsules. By investigating surface tension and zeta potential of NaCMC with the mixture of sodium dodecyl sulfate (SDS)/perfluoro-nonene oxy benzene sulfonate (OBS), we found that both the presence of hydrophobic interaction and the hydrogen bonding between NaCMC and SDS/OBS enhanced the adsorption of NaCMC at the oil/water interface and thus facilitated the formation of capsule wall. The morphology, particle size, surface free energy and thermal stability of the obtained microcapsules were characterized. The results showed that optically transparent microcapsules with uniform size, smooth surface and compact wall can be obtained by adjusting the pH value of the reaction system and the concentration ratio of SDS/OBS. Based on the prepared microcapsules, a matrix display prototype operated at 9 V direct current in static driven mode was fabricated.