STAR-SHAPED POLY(2,6-DIMETHYL-1,4-PHENYLENE ETHER)

The properties of star-shaped poly(2,6-dimethyl-1,4-phenylene ether) ( PPE), as prepared by the redistribution of PPE and tyrosine-modified p oly(propylene imine) dendrimers, are studied in solution and in 50/50 wt% blends with linear polystyrene. Star polymers with constant armlen gth but increasing number of arms show the same hydrodynamic volume as measured by Size Exclusion Chromatography (SEC), but decreasing hydro dynamic radius as measured by Dynamic Light Scattering (DLS). This is caused by the restricted mobility of the more densely packed chains at high numbers of arms, also leading to a decrease in intrinsic viscosi ties. These solution properties are also reflected in the miscibility behaviour in polymer blends. Star-shaped polymers with a high number o f PPE arms (16,32 or 64 respectively) give inhomogeneous blends with l inear polystyrene, in contrast to the miscible combination of linear p olystyrene with linear PPE or starshaped polymers with a low number (4 or 8) of PPE arms.