Cyclic and Multiblock Polystyrene-block-polyisoprene Copolymers by Combining Anionic Polymerization and Azide/Alkyne “Click” Chemistry

• Published in: Macromolecules Vol. 44; no. 7; pp. 1969 - 1976
• Main Authors: Touris, Athanasios, Hadjichristidis, Nikos
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 12.04.2011
• Subjects: Applied sciences; Copolymerization; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Preparation, kinetics, thermodynamics, mechanism and catalysts; Linear copolymer; Intramolecular reaction; 1,3-Dipolar cycloaddition; End group; Chain elongation; Cyclic copolymer; Experimental study; Azides; Monodispersed polymer; Chemical modification; Cyclization; Multiblock copolymer; Preparation; Isoprene copolymer; Diblock copolymer; Triazole copolymer; Anionic copolymerization; Intermolecular reaction; Nucleophilic substitution; Styrene copolymer
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma102900d

An α,ω-heterotelechelic block copolymer of polystyrene (PS) and polyisoprene (PI), α-acetylene-ω-azido-PS-b-PI, with Μ n = 18 900 and PDΙ = 1.05, was synthesized by (a) sequential anionic polymerization of styrene and isoprene with 5-triethylsilyl-4-pentynyllithium (TESPLi) as initiator to afford α-(TES-acetylene)-ω-lithium-PS-b-PI, (b) reaction of the living heterofunctionalized copolymer with 1,4-dibromobutane and sodium azide to give α-(TES-acetylene)-ω-azido-PS-b-PI, and (c) deprotection of the acetylene group to afford the final product α-acetylene-ω-azido-PS-b-PI. This α,ω-heterotelechelic block copolymer with “clickable” groups, in the presence of CuBr and N,N,N′,N′′,N′′-pentamethyldiethylenetriamine, led to cyclic block copolymer in dilute solution (lower than the equilibrium concentration <6 × 10−5 g/mL), whereas in concentrated solutions (5.3 × 10−2 g/mL) gave multiblock copolymers.