Synthesis, characterization, and fluorescence of pyrene-containing eight-arm star-shaped dendrimer-like copolymer with pentaerythritol core

Novel and well-defined pyrene-containing eight-arm star-shaped dendrimer-like copolymers were successfully achieved by combination of esterification, atom transfer radical polymerization (ATRP), divergent reaction, ring-opening polymerization (ROP), and coupling reaction on the basis of pentaerythritol. The reaction of pentaerythritol with 2-bromopropionyl bromide permitted ATRP of styrene (St) to form four-arm star-shaped polymer (PSt-Br)(4). The molecular weights of these polymers could be adjusted by the variation of monomer conversion. Eight-hydroxyl star-shaped polymer (PSt-(OH)(2))(4) was produced by the divergent reaction of (PSt-Br)(4) with diethanolamine. (PSt-(OH)(2))(4) was used as the initiator for ROP of epsilon-caprolactone (CL) to produce eight-arm star-shaped dendrimer-like copolymer (PSt-b-(PCL)(2))(4). The molecular weights of (PSt-b-(PCL)(2))(4) increased linearly with the increase of monomer. After the coupling reaction of hydroxyl-terminated (PSt-b-(PCL)(2))(4) with 1-pyrenebutyric acid, pyrene-containing eight-arm star-shaped dendrimer-like copolymer (PSt-b-(PCL-pyrene)(2))(4) was obtained. The eight-arm star-shaped dendrimer-like copolymers presented unique thermal properties and crystalline morphologies, which were different from those of linear poly(epsilon-caprolactone) (PCL). Fluorescence analysis indicated that (PSt-b-(PCL-pyrene)(2))(4) presented slightly stronger fluorescence intensity than 1-pyrenebutyric acid when the pyrene concentration of them was the same. The obtained pyrene-containing eight-arm star-shaped dendrimer-like copolymer has potential applications in biological fluorescent probe, photodynamic therapy, and opto-electronic devices. (c) 2008 Wiley Periodicals, Inc.