Ruthenium-catalyzed cascade metathetical cyclopolymerization of bisnorbornenes with flexible linkers

Abstract

Treatments of bisnorbornenes tethered by a flexible linker (triethylene glycol, tetramethylene moiety, or crown ether) with the first generation of Grubbs catalyst give the corresponding single-stranded polybisnorbornenes via cascade metathetical cyclopolymerization (CMCP). The structures of these polymers were proved by spectroscopic means, MALDI-TOF mass spectrometry, gel permeation chromatography, and dynamic light scatterings as well as by chemical degradation via hydrolysis followed by esterification. The presence of N-aryl pendants to connect the norbornene moiety and the flexible linker is crucial for the success of such CMCP process. Presumably, intramolecular π-π interactions between the pending aryl groups may take place to direct the ring closure process. Substrates without such N-aryl pendants give a mixture of single- and double-stranded polynorbornenes in addition to cross-linking polymers. © 2013 American Chemical Society.