Intramolecular Hydrogen-Bond-Based Latent Initiator for Olefin Metathesis Polymerization

Abstract

Latent olefin metathesis polymerization catalysts have enormous potential, as they provide access to thermoset polymers. However, developing a novel latent catalyst is difficult because the catalyst must be inactive at room temperature and completely convert the starting material to the product upon activation. Herein, we report the synthesis of a series of novel initiators 1–4 bearing an additional hydrogen donor that can form a weak hydrogen bond with the metal-bound chloride anion of the active species of an alkylidene-containing N-heterocyclic carbene (NHC)-Ru-based initiator, and their latent catalytic behavior was examined in the ring-opening olefin metathesis polymerization (ROMP) of dicyclopentadiene (DCPD) and cyclooctadiene (COD). The presence of intramolecular hydrogen bonds in initiators 1 and 2 facilitates latent polymerization, whereas the absence of intramolecular hydrogen bonds in initiators 3 and 4 allowed polymerization of DCPD at 30 °C. The TGA and DSC results for poly-DCPD (PDCPD) suggest that the intramolecular hydrogen bonding in initiators 1 and 2 did not alter the nature of the NHC-Ru-based initiator at 80 °C.

Storable, Dual-Component Systems for Frontal Ring-Opening Metathesis Polymerization

“…e ., temperature and ν f ) and materials properties of the polymer products . Given these challenges, we sought to adapt a soluble, latent catalyst for FROMP. − …”

“…While a plethora of thermally − or photolytically triggerable ,, catalytic systems exist for bulk ROMP, several major challenges exist for application to FROMP. Many of these tailor-made catalytic species require multistep syntheses, which precludes application to industrially relevant scales.…”

Preparation and properties of an interpenetrating network polymer based on polydicyclopentadiene and phenolic resin

“…When the content of the phenolic resin is high, a large number of cyclopentene ring double bonds of DCPD react with hydroxyl groups of phenolic resin during the polymerisation process to form a linear crosslinked structure, and this part of the double bonds cannot be crosslinked with itself, thus reducing the crosslinking degree of PDCPD. 20,21 This argument is also reflected in the FT-IR spectrum. Another reason for the decrease of the crosslinking degree is that in the crosslinking process, the hydrogen atom provided by PF first occupies the site of the DCPD double bond, and thus polymerizes with PDCPD, which inhibits the "radical" contribution of crosslinking, thus reducing the crosslinking degree of PDCPD.…”

Olefin Metathesis Catalyzed by a Hoveyda–Grubbs-like Complex Chelated to Bis(2-mercaptoimidazolyl) Methane: A Predictive DFT Study

“… 20 Other examples encompass Ru–N chelating agents like amidobenzylidene that shows catalytic activity in acidic medium 21 or carbamate and acetamide that induce metathesis more effectively in the presence of RuCl 2 ···H weak bonds compared to similar catalysts lacking such H bonds. 22 …”

“…Interestingly, the incorporation of a chelating ligand, such as 2-isopropoxystyrene, in Hoveyda–Grubbs ( HG ) catalysts revealed new opportunities in tuning catalytic properties through substituent variation in the styrene fragment. , For example, the substitution of NO 2 prepared by Grela made possible an efficient low-temperature metathesis, which is attributed to the electron-withdrawing effect of the NO 2 moiety, that weakens the Ru–O bond strength . Other examples encompass Ru–N chelating agents like amidobenzylidene that shows catalytic activity in acidic medium or carbamate and acetamide that induce metathesis more effectively in the presence of RuCl 2 ···H weak bonds compared to similar catalysts lacking such H bonds …”