Synthesis of multicyclic polymers by intramolecular cyclization via a “tail-biting” strategy and their characterization

Abstract

This paper elaborates the preparation of “flower-shaped” tricyclic and hexacyclic polymers by intramolecular cyclization via a “tail-biting” strategy. Multifunctional initiators with equal amounts of alkynyl groups and 2-bromoisobutyrate groups are synthesized by catalyst-free azide-alkynyl click reaction, and then used in atom transfer radical polymerization (ATRP) of styrene to afford multiarm star polystyrenes (PS). After azidation of terminal bromines, multicyclic polymers are prepared by intramolecular cyclization via Cu-catalyzed azide-alkynyl cycloaddition (CuAAc) click reaction between terminal azide groups and interior alkynyl groups. Structures of tricyclic and hexacyclic polystyrenes are characterized by 1H NMR, GPC and FT-IR. Fluorescence emissions of initiators and polymers are observed, and the influence of topology on fluorescence intensity is discussed.