Influence of molecular weight on stepwise collapse of Langmuir monolayers of cyclolinear polyorganosiloxanes

Abstract

 The series of hexacyclo-linear polyorganosiloxanes containing methyl and phenyl side groups, which differ by molecular weight and tacticity, were analyzed for the dependence of surface pressure on surface area per monomer unit. The effects of temperature and the nature of substrate were also investigated. All the polymers investigated are capable of forming Langmuir monolayers on the surfaces of liquid substrates. Being under compression, the monolayers of these polymers are able to form discrete multilayers. This property is closely related to the existence of thermodynamically stable mesophase in cyclolinear polyorganosiloxanes. It has been established that formation of the multilayers in these polymers is quite sensitive to the molecular weight of the polymer. This effect is explained by a change in the value of the shear module of the polymer with molecular weight.