ORDERING PHENOMENA OF STAR POLYMERS IN SOLUTION BY SANS

In this paper we present the experimental evidence of incipient ordering of star polymers in solution near the overlap concentration-phi* as predicted by scaling laws. We have studied 8- and 18-arm polyisoprene stars in the dilute and semi-dilute regime. A peak in the interparticle structure factor S(Q) due to a liquidlike ordering of spheres was found by small-angle neutron scattering. A shift of the peak position to higher Q was observed with increasing concentration. The corresponding mean particle distance 2-pi/Q(max) scales with phi--1/4 for both stars. Our results, in accordance with predictions, follows the general scaling behavior.