ARM-NUMBER DEPENDENCE OF DIMENSIONS OF STAR-SHAPED POLYSTYRENE IN A GOOD SOLVENT

Radii of gyration R(g) and hydrodynamic radii R(h) of star-shaped polystyrenes with different arm numbers and their arm polymers were measured in toluene solution by static and dynamic light scattering. R(h) depends on the number of arms f stronger than R(g). The ratios g(g)a = R(g) (star)/R(g)(arm) and g(h)a = R(h) (star)/R(h) (arm) were compared with other experimental and computer simulation results to examine the universality of these ratios. Universality of the relation of g(g)a versus number of arms f is confirmed. No clear indication of failure of g(h)a in universality is observed, and it was suggested that g(h)a is not sensitive to systems. Experimental results were also compared with available theories. The renormalized two-parameter theory by Douglas and Freed for static quantities g(g)a and g(A) (= A2 (star)/A2 (linear), where A2 is the second virial coefficient) reproduces the experimental data very well at lower fs and agreement in g(g)a is excellent over a wide range of f.