Polymer, Vol.119, 245-252, 2017
Synthesis of fluorescent hyperbranched enediynes and Bergman cyclization polymerization for generating spatially locked persistent radicals
A series of AB(2) type monomers with terminal alkyne (A) and iodine (B) were synthesized from dichloromaleic anhydride by amidation with terminal alkynylamine followed by chlorine-iodine exchange reaction. Starting from these AB2 monomers, three kinds of fluorescent hyperbranched polymers with enediyne repeating units (HBEP1 similar to HBEP3) were synthesized via one-pot Sonogashira cross coupling polymerization reaction. The HBEPs was characterized by a variety of techniques and the degree of branching (DB) of the HBEPs were determined by H-1 NMR spectroscopy. The molecular weights (M-n) of HBEPs are up to 73 kDa and the DBs are up to 0.97, close to that for a dendrimer. Due to the different degree of conjugation of these HBEPs, the HBEPs display different photo-luminescence and excitation dependent fluorescence behavior. These HBEPs were further subjected to thermal Bergman cyclization to generate crosslinked polymeric networks with spatially locked persistent radicals. EPR experiments showed that the free radicals in these materials were stable for a long time at room temperature and can be slowly quenched when exposed to air, providing a promising application as long-term free radical cleaner. (C) 2017 Elsevier Ltd. All rights reserved.