Special features of structuring in carboxyl-containing polydimethylcarbosiloxanesстатья
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Дата последнего поиска статьи во внешних источниках: 8 августа 2017 г.
Аннотация:The physicochemical properties (viscosity, elastic modulus, thermomechanical properties) of polydimethyl-carboxysiloxanes containing lateral carboxyl groups in the macromolecule with a distance between them of 30–80 siloxane units over the temperature range 20–160°C is studied. Increase in temperature above 80°C leads to structuring of the polymers and their passage from the liquid into the high elastic state. The elastic modulus of the polymer, and also the shift of the glass transition temperature and the fluidity are directly related to the temperature and the duration of heating and to the carboxyl group content in the macromolecule. The phenomenon is reversible in character, and when the heated elastic sample is held for a long period at room temperature it changes completely to the original liquid state. The results are interpreted from the point of view of the change in the type of bond with rise in temperature (passage from intra- to intermolecular hydrogen bonds) or the formation of clusters at the cross-links of the physical network.