Interfacial behaviors of densely anchored hydrophilic oligomeric chains on silica microspheres

Abstract

This work studies the interfacial behaviors of a thickly grafted hydrophilic oligomeric layer on silica microspheres ( $$\overline d \cong 1\;{\text{ $ \mu $ }}{\kern 1pt} m$$ ). The surface layer comprises the homopolymer or block-copolymer chains of sodium 4-styrenesulfonate (SSNa) and 4-vinylpyridine (4VP). Such a core-shell microspheric structure is constructed by the atom transfer radical polymerization method. Two types of block-copolymer chains are synthesized through reversing the chain growing sequence of PSSNa and P4VP blocks, a copolymer double layer is, therefore, generated. It is found that these two block-sequences produce rather different impacts on the chain–chain interaction patterns. Furthermore, the functional group type and the sequence of the grafted copolymer blocks influence the hydrodynamic volume of the particles in the designated dispersion media with different pH or polarity. More appealingly, the two types of double-layers exhibit very different roles in mediating ion (H+ or Na+) transport in the liquid medium where a substantially low content of the microspheres is present.