THE EFFECT OF RING SIZE AND THE NATURE OF SIDE-GROUPS IN CYCLOLINEAR POLYSILOXANES ON THEIR ABILITY TO FORM LANGMUIR FILMS

Monomolecular films formed by cyclolinear polysiloxanes were studied b y measuring surface pressure as a function of the area per single silo xane group in the main chain of polymer. The effects of ring size (fro m 4 to 7 siloxane groups in the ring) and side substituents (methyl, e thyl, propyl, phenyl radicals and their combinations) were studied. It was found that most cyclolinear polysiloxanes are able to form monola yers at the water surface regardless of the ring size and the nature o f side substituents in spite of the fact that their linear analogs (po lydiethyl-, polydipropyl-, and polydiphenylsiloxanes) do not form such films. Like in the case of cyclolinear polydecamethylhexasiloxanes, f or most of the polysiloxanes studied here, the compression isotherm is described by a multistep pattern, which is related to their self orga nization into discrete multilayer structures. However, the magnitude o f pressure required to form a new monolayer, the area, and the number of layers are controlled by the ring size and the nature of side subst ituents.