Simple access to alkoxysilyl telechelic polyolefins from ruthenium-catalyzed cross-metathesis depolymerization of polydienes

Tandem metathesis depolymerization and cyclopolymerization toward flexible-rigid block copolymer with unique damping properties

Metathesis depolymerization (MDP) of natural rubber (NR) was readily conducted to afford depolymerized NR (dNRx) bearing the living chain end, which can initiate metathesis cyclopolymerization (MCP) of 1,6-heptadiyne monomers to...

Selectively Depolymerizable Polyurethanes from Unsaturated Polyols Cleavable by Olefin Metathesis

This communication describes a novel series of linear and crosslinked polyurethanes (PUs) and their selective depolymerization under mild conditions. Two unique polyols are synthesized bearing unsaturated units in a configuration designed to favor ring-closing metathesis (RCM) to five- and six-membered cycloalkenes. These polyols are co-polymerized with toluene diisocyanate to generate linear PUs and trifunctional hexamethylene- and diphenylmethane-based isocyanates to generate crosslinked PUs. The polyol design is such that the RCM reaction cleaves the backbone of the polymer chain. Upon exposure to dilute solutions of Grubbs' catalyst under ambient conditions, the PUs are rapidly depolymerized to low molecular weight, soluble products bearing vinyl and cycloalkene functionalities. These functionalities enable further re-polymerization by traditional strategies for polymerization of double bonds. It is anticipated that this general approach can be expanded to develop a range of chemically recyclable condensation polymers that are readily depolymerized by orthogonal metathesis chemistry.

One-step Synthesis of End-Functionalized Hydrogenated Nitrile-Butadiene Rubber by Combining the Functional Metathesis with Hydrogenation

End-functionalized hydrogenated polymers obtained from nitrile-butadiene rubber (NBR) yield new materials with suitable properties for a number of applications as sealing material and adhesives. We investigated the one-step synthesis of ester end-functionalized hydrogenated nitrile-butadiene rubber (EF-HNBR) by combining the functional metathesis with the hydrogenation of NBR in the presence of the 2nd generation Grubbs catalyst and a functionalized olefin as a chain transfer agent (CTA). We established the operating conditions for the effective production of saturated functional polymers with a high degree of hydrogenation, high chemo-selectivity and moderate molecular weight. The structures of the products were confirmed by FT-IR and 1H-NMR spectroscopy, rubber molecular weight, and distribution determined by using gel permeation chromatography (GPC); their thermal properties were determined by thermo-gravimetric analysis (TGA) and different scanning calorimetry (DSC).

Olefin metathesis in multiblock copolymer synthesis

Multiblock copolymers constitute a basis for an emerging class of nanomaterials that combine various functional properties with durability and enhanced mechanical characteristics. Our mini-review addresses synthetic approaches to the design of multiblock copolymers from unsaturated monomers and polymers using olefin metathesis reactions and other ways of chemical modification across double C=C bonds. The main techniques, actively developed during the last decade and discussed here, are the coupling of end-functionalized blocks, sequential ring-opening metathesis polymerization, and cross metathesis between unsaturated polymers, or macromolecular cross metathesis. The last topic attracts special interest due to its relative simplicity and broad opportunities to tailor the structure and hence the properties of the copolymer products. Whenever possible, we analyze the structure-property relations for multiblock copolymers and point to their possible practical applications.

Preparation and property investigation of chain end functionalized cis-1,4 polybutadienes via de-polymerization and cross metathesis of cis-1,4 polybutadienes

The end-functional cis-1,4 polybutadiene displayed improved thermal stability and mechanistic properties.

α,ω-Epoxide, Oxetane, and Dithiocarbonate Telechelic Copolyolefins: Access by Ring-Opening Metathesis/Cross-Metathesis Polymerization (ROMP/CM) of Cycloolefins in the Presence of Functional Symmetric Chain-Transfer Agents

Epoxide- and oxetane-α,ω-telechelic (co)polyolefins have been successfully synthesized by the tandem ring-opening metathesis polymerization (ROMP)/cross-metathesis (CM) of cyclic olefins using Grubbs' second-generation catalyst (G2) in the presence of a bifunctional symmetric alkene epoxide- or oxetane-functionalized chain-transfer agent (CTA). From cyclooctene (COE), trans,trans,cis-1,5,9-cyclododecatriene (CDT), norbornene (NB), and methyl 5-norbornene-2-carboxylate (NB^COOMe), with bis(oxiran-2-ylmethyl) maleate (CTA 1), bis(oxetane-2-ylmethyl) maleate (CTA 2), or bis(oxetane-2-ylmethyl) (E)-hex-3-enedioate (CTA 3), well-defined α,ω-di(epoxide or oxetane) telechelic PCOEs, P(COE-co-NB or -NB^COOMe)s, and P(NB-co-CDT)s were isolated under mild operating conditions (40 or 60 °C, 24 h). The oxetane CTA 3 and the epoxide CTA 1 were revealed to be significantly more efficient in the CM step than CTA 2, which apparently inhibits the reaction. Quantitative dithiocarbonatation (CS₂/LiBr, 40 °C, THF) of an α,ω-di(epoxide) telechelic P(NB-co-CDT) afforded a convenient approach to the analogous α,ω-bis(dithiocarbonate) telechelic P(NB-co-CDT). The nature of the end-capping function of the epoxide/oxetane/dithiocarbonate telechelic P(NB-co-CDT)s did not impact their thermal signature, as measured by DSC. These copolymers also displayed a low viscosity liquid-like behavior and a shear thinning rheological behavior.

Advances in the synthesis of silyl-modified polymers (SMPs)

Silyl-modified polymers (SMPs) are being synthesized from chemical modification and olefin metathesis strategies.

Converting natural rubber waste into ring-opening metathesis polymers with oligo-1,4-cis-isoprene sidechains

Cross-metathesis with acrylates is used as the key-step to recycle natural rubber waste.