Polymeric amphiphiles at solid-fluid interfaces: Forces between layers of adsorbed block copolymers

AUTOR(ES)

Tirrell, Matthew

RESUMO

Block copolymers are macromolecular amphiphiles and as such have a wide variety of interesting interfacial behavior. We present here a case of block copolymer adsorption from solution studied by the direct measurement of forces between two adsorbed layers. The case is polystyrene (PS)-poly(2-vinylpyridine) (PVP) adsorbed on mica from toluene. Under these circumstances a layer of firmly anchored PS cilia (or loops in the case of PVP-PS-PVP tri-blocks) is assembled on the surface. Furthermore, the PS cilia adopt an extended chain configuration due to lateral crowding imposed on them by the high graft density. The long-range repulsive forces measured in toluene are direct evidence for the well-known efficacy of this sort of macromolecule in the stabilization of colloidal dispersions. The picture of the adsorbed configuration for di-block copolymers is reasonably clear; that for tri-blocks is less so. Some thoughts are offered on new experiments and technological uses of these materials.

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