| Abstract
| - The relationships between the viscoelastic and structural properties of glass-forming materials with polysiloxanebonds, which serve as network formers, and phenyl groups, which act as network terminators, are examinedbased on shear viscoelasticity, 29Si MAS NMR, and GPC measurements during the early stages of the network-forming process. The viscosities of the present samples do not depend on the frequency at temperatures upto 200 °C, suggesting that the origin of the viscous flow does not include intermolecular entanglement.According to the results of the strain dependence of the elastic modulus, the bridging-oxygen number, andmolecular weight, the present polysiloxane system has a complex structure, or distribution of various-sizedmolecules composed of a polysiloxane network with various dimensionalities, and furthermore an elementaryprocess of the viscosity is simple flow of these molecules. The structural factors that determine the viscosityand its temperature dependence are categorized into the molecular size and the intramolecular structure byusing a theory based on the free-volume model. The relationship between the viscosity and the structurearound the glass transition temperature is quantitatively examined and it is concluded that introducing largernumbers of Ph groups makes the viscosity less sensitive to structural factors.
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