Abstract
Abstract The synthesis of well-defined, near monodisperse, nonlinear block copolymers of the A2B (3-miktoarm star copolymers), A3B (4-miktoarm star copolymers), (AB)2(BA)2 (inversed 4-miktoarm star block copolymers), and A3BA3 (bridged miktoarm star copolymers) types is described. A is polyisoprene (PI) and B is polystyrene (PS). The synthetic approach involves the reaction of methyltrichlorosilane or tetrachlorosi-lane with monofunctional or difunctional macroanions of B under conditions unfavorable to chain coupling or linking, followed by addition of the monofunctional macroanion A. Characterization was carried out by size exclusion chromatography, low-angle laser light scattering, laser differential refractometry, membrane and vapor pressure osmometry, and NMR and UV spectroscopy. Microphase separation was studied by transmission electron microscopy and small-angle x-ray scattering. Comparison with the corresponding linear block copolymers showed that the macromolecular architecture not only strongly affects the morphological domain borders but can introduce new morphologies as well.
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