| Popis: |
Copolymers of acrylonitrile (M 2 ) and two methacrylate-ended polysiloxane (PDMS) macromers have been prepared and characterized. As in previous investigations, the errors in r 1 render their values meaningless. Values of r 2 could be determined with more precision and increased from 0.41 to 0.89 as the molecular weight ( M n ) of the macromer increased from 500 to 1100. This effect, which has been noted previously, is probably due to a steric or excluded-volume effect, possibly involving repulsion between the growing chain and that of the macromer chain. Differential scanning calorimetry examination showed that the copolymers had a two-phase morphology comprising polyacrylonitrile and PDMS domains. There was slight interpenetration of one domain by the other and the PDMS exerted a significant plasticizing effect on the glassy domain only when the macromonomer content exceeded 60–70% by weight. The general lack of miscibility can be ascribed to the relatively high degree of incompatibility between PDMS and polyacrylonitrile. |
