Synthesis and characterization of ring-opening metathesis polymers bearing functional imidazole end group

Ring-opening metathesis polymerization (ROMP) is an efficient synthetic method that is used in the synthesis of polymeric structures bearing functional groups. Macromolecules bearing chain-end functional groups can be synthesized using the terminal and internal olefins as chain transfer agent via ROMP/cross-metathesis (CM) reactions. ROMP polymers bearing functional end groups are used in a variety of different fields such as biosensor applications, the development of hybrid materials, in the synthesis of polymeric ligand precursors. Up to date, a great variety of functional groups were integrated into chain ends of ROMP polymers, however, no ROMP polymers bearing imidazole end groups have yet been reported in the literature. Imidazole derivatives are frequently used in macromolecular chemistry owing to their unique properties such as biocompatibility, acting as ligand and ionomer precursors and as the metal scavenger in the form of imidazolium salts. The direct integration of imidazole groups to chain ends of ROMP polymers is not possible due to the poisoning of Grubbs type catalyst by imidazole groups. In this study, to overcome the above-mentioned difficulties, polycyclooctene derivatives bearing imidazole end groups were synthesized for the first time with a two-step procedure using ROMP/CM and aminolysis reactions. Cyclooctene (COE) was polymerized via ROMP reactions in the presence of first generation Grubbs catalysts (G1) using methyl-10-undecenoate (MU) as chain transfer agent (CTA). Polycyclooctenes bearing mono ester end group was obtained as the major product. Imidazole end-functionalized poly cyclooctenes were synthesized with aminolysis reactions between ester end-capped polycyclooctene derivatives and 1-(3-aminopropyl)-imidazole groups. All polymeric products were characterized by means of 1H and 13C NMR spectrometry, matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-ToF/MS), size exclusion chromatography (SEC). Keywords: Ring-Opening Metathesis Polymerization, Chain Transfer Agent, Imidazole, Cross-Metathesis, Ruthenium