Thermal activation of polyethylene@silica particles: Towards ceramic surfactants

The fabrication of "switch-on" amphiphilic submicrometer hybrid particles of cross-linked polyethylene (XPE)@silica is described. The synthesis of the particles is based on the simultaneous cross-linking of PE and the polycondensation of tetraethoxysilane in hot, surfactant-stabilized O/W micelles. Thermal activation of the particles results in particles with amphiphilic behavior. It is proposed that the thermal activation triggers partial phase-separation which pushes some of the PE chain to the surface, in a heterogeneous way. By this, on each particle two halves can be identified which differ in their degree of hydrophobicity ("Janus" structure), thus giving rise to the surfactant activity. The particles were intensively characterized before and after the thermal activation and their amphiphilic behavior was demonstrated. By the approach described in the paper it is in principle possible to design a library of functionalities out of a single surface active agent species. This was demonstrated by the thermal activation of functionalized composite particles of dyes@XPE@silica and of the triple hybrid Ag@XPE@silica. Full material characterization is provided, including SEM, TGA, surface area analysis, antibacterial tests and zeta potential measurements.