ADMET Polymerization as a Route to Functionalized Polycarbosilanes

Abstract

It is now evident that ADMET chemistry can be employed to prepare a family of unsaturated carbosilane polymers containing a common backbone decorated with different alkoxysilane pendant groups, demonstrating the generality and potential utility of this chemistry. Four functionalized silicon containing dienes have been synthesized by nucleophilic substitution of the same parent diene monomer containing two reactive silicon‐chlorine bonds. These new α,ω‐diene monomers have been polymerized under ADMET conditions using the 2nd generation Grubbs's ruthenium catalyst, producing polymers with useful molecular weights. Variation of the pendant group results in differing chemical and physical properties of the resulting polymers. We believe this chemistry offers much to broaden the synthetic pathways to new organosilicon polymers. magnified image

Three‐dimensional computed tomography in the cardiac catheterization laboratory

“…The presence of reactive groups in each repeat unit of the polymer makes the characterization and handling of polymer challenging. Hydrolytic sensitivity makes GPC analysis unavailable, instead 1 H NMR end‐group analysis was performed indicating a Mn of 45,000 g/mol, four times higher than previously reported 58. Differential scanning calorimetry was performed yielding the same glass transition ( T g = −80 °C) as observed by Church et al…”

“…Indeed, metathesis does occur and can be easily observed by the disappearance of both the internal and external olefin protons at 5.8 and 5.0 ppm, respectively. This unsaturated carbosilane has been previously synthesized by Church58 et al during investigation of nucleophilic substitution on silicon‐containing α,ω‐dienes; however, 2nd generation Grubbs' ruthenium complex was used to promote ADMET polymerization.…”

Functional Precision Polymers via Stereo‐ and Regioselective Polymerization Using Group 6 Metal Alkylidene and Group 6 and 8 Metal Alkylidene N‐Heterocyclic Carbene Complexes

“…In case centrosymmetric monomers of the general formula H 2 CCH‐(CH 2 ) n ‐X‐(CH 2 ) n ‐CHCH 2 are used, polymers with a precise positioning of the X‐group along the polymer chain are formed. Depending on the catalyst employed, X can contain functional groups such as halo‐groups, esters, amides, carbosilanes (Schrock‐ and Grubbs‐type catalysts) but also carboxylic acids, boronic acids and esters, amino acids, phosphonates, phosphoramidates, thienylene vinylenes, diketopiperazines, or alcohols (Grubbs‐type catalysts). [6b,46] With prochiral dienes, only atactic polymers have been prepared so far; however, the issue of tacticity can be avoided using dienes in which X contains two identical substituents, that is, X = CR 2 .…”

Chain‐End and Chain‐Internal Crosslinking in “Latent Reactive” Silicon Elastomers

“…A few research groups have used this methodology to synthesize carbosilane/carbosiloxane copolymers bearing alkoxy or halide groups as well as the incorporation of disilacyclobutanes. [65,[70][71][72][73][74][75] For example, we have demonstrated the presence and significance of introducing ''chain-internal'' latent reactive silicon-methoxy bonds permitting the synthesis of a linear elastomer which can be easily shape processed. [65] Recently, Interrante and co-workers have synthesized carbosilane copolymers where the disilacyclobutane rings were imbedded into the copolymer's backbone.…”