Study of Self-Diffusion of Silicone MQ Resins in Chloroform Solutions by Pulsed Field-Gradient NMR Spectroscopy

The self-diffusion of silicone MQ copolymers in solutions with chloroform was studied by pulsed field-gradient nuclear magnetic resonance over a wide range of macromolecular concentrations. The highly branched structure of the molecules reveals some characteristic features of the translational mobility. The studies were performed with the initial MQ copolymer as well as with the narrow-dispersed fractions obtained from it. The data indicate the differences in dynamics between fractions. The appearance of the species with different self-diffusivity with increasing of the polymer concentration in solutions was observed. Such behavior was attributed to the formation of aggregates of macromolecules in solution. The results show that the molecular weight influences the diffusion behavior of the MQ resins in solutions. The diffusion of the MQ resins reveals features characteristic for rigid macromolecular structures rather than flexible polymers. Differences in translational dynamics of MQ copolymers, linear flexible polymers and particle-like macromolecules are discussed.