Structural and Mechanical Behavior of Polymethylmethacrylate Containing Diethyl Siloxane Oligomer

Using the method of positron annihilation, structural changes induced by introduction of diethyl siloxane oligomers to PMMA were studied. The effect of these structural changes on the mechanical behavior of PMMA was discussed in terms of structural inhomogeneity of PMMA: existence of structural sublevels with different packing density and ordering. Deformation of glassy polymers at low strains as well as such mechanical characteristics as yield stress and contribution of low-temperature component to the temperature-induced relaxation of plastic deformation were shown to be controlled by segmental mobility in structural sublevels with a lower packing density.