MORPHOLOGY OF VERGINA STAR 16-ARM BLOCK-COPOLYMERS AND SCALING BEHAVIOR OF INTERFACIAL AREA WITH GRAFT POINT FUNCTIONALITY

The morphological behavior of three well-defined miktoarm star block c opolymers having 16 arms/molecule was characterized using transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), and s mall-angle neutron scattering (SANS) techniques. The molecules, called Vergina stars, have 8 arms of polyisoprene and 8 arms of polystyrene radiating from a single junction point. The samples, with polystyrene volume fractions of 0.37, 0.44, and 0.47 and total molecular weights r anging from 330 000 to 894 000, were all found to microphase separate into lamellar morphologies. In this respect all three samples, in agre ement with theory, behave in the same way as linear diblock copolymers of the same relative volume fractions. Incorporating results from pre vious studies in the literature of miktoarm block copolymers containin g trifunctional and tetrafunctional branch points, as well as the new Vergina star data, the scaling behavior of the area per junction versu s junction functionality was investigated.