Star - block -linear - block -star triblock polystyrene polymers with identical stars at each end of a linear block (pom-pom polymers) were synthesized by the convergent living anionic polymerization method. The sequential synthesis involved first the formation of a living anionic polystyrene star with a hyperbranched core via continuous addition of coupling agent, 4-(chlorodimethylsilyl)styrene, to living polystyrene chains. Subsequent addition of styrene monomer to the living polystyrene star anions produced star - block -linear diblock polystyrene anions that were then coupled with dichlorodimethylsilane to make the architectural triblock. The obtained pom-pom polymers were purified by fractionation. Gel permeation chromatography−multiangle laser light scattering characterization clearly showed the molecular weight changes due to the progression of polymerization. The star - block -linear - block -star triblock copolymers were characterized by NMR ( 1 H and 29 Si) spectroscopy and dilute solution viscometry. The architectural triblock copolymers demonstrate interesting dilute solution properties.
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Knauss et al. (2002) studied this question.
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