Macromolecules, Vol.30, No.8, 2373-2376, 1997
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 copolymers having 16 arms/molecule was characterized using transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), and small-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 ranging from 330 000 to 894 000, were all found to microphase separate into lamellar morphologies. In this respect all three samples, in agreement with theory, behave in the same way as linear diblock copolymers of the same relative volume fractions. Incorporating results from previous studies in the literature of miktoarm block copolymers containing trifunctional and tetrafunctional branch points, as well as the new Vergina star data, the scaling behavior of the area per junction versus junction functionality was investigated.