Conformation and rigidity of ladder polymer molecules

Abstract

Two new samples of cyclo-linear polyphenyl-siloxane (CLPhS) and a sample of cyclo-linear poly-3-methyl-butene-1 silsesquioxane (CLMBS) have been investigated by viscometry, diffusion, sedimentation and flow birefringence methods. The size of the Kuhn statistical segment ( A), characterizing the rigidity of macromolecules, was determined from hydrodynamic models using the theory of a persistent model. The values of A greatly exceed the corresponding values for flexible (coil-shaped macromolecules) and for linear siloxanes. This confirms the ladder structure of the double main chain of the polymers under investigation. The values of segmental anisotropy, anisotropy of the monomer unit and the unit length of the macromolecules in the CLPhS samples were determined from dynamooptical properties. A comparison of the rigidity for the three CLPhS samples investigated (one of them studied previously) shows that it is different for different samples. This fact suggests that the flexibility mechanism of polymers of this type is affected by the defectiveness of structure, i.e. by the occurrence of single bonds in the main chain. It is shown that the study of hydrodynamic and optical properties of the molecules of such polymers may serve as a sensitive method for detection and quantitative investigation of defectiveness of structure.