Acetals ADMET polymerization

The molybdenum catalyst 2 has been used extensively for ADMET polymerization. This complex is easier to handle than the tungsten analog and is more tolerant of functionality. This complex has allowed the synthesis of polymers containing esters, carbonates, ethers, sulfides, aromatic amines, boronates, dichlorosilanes, siloxanes, acetals, and conjugated carbon-carbon double bonds [38-45]. Aldehydes, ketones, and protic functionahty are not tolerated. The molybdenum alkylidene will react with aldehydes and ketones, but not esters, in a Wittig fashion [64]. 

Watson and Wagener [95] reported a tandem ADMET polymerization/ hydrogenation approach to acetoxy-end-functionalized telechelic polyethylene. DCD was polymerized in the presence of 9-decenyl acetate to form the corresponding di-ester-functionalized homo-telechelic polymer. The crude unsaturated polymer was intimately mixed with silica gel and exposed to 120 psi of H2 at 90 °C. The silica gel was added to suppress catalyst homo-dimerization, and the hydrogenated polymer was recovered as the di-ester-functionalized telechelic polyethylene with a molecular weight of 1.5 X 10 g moD fDP = 48) and a PDI of 1.9. 

Monomers with multiple ether functionalities have also been polymerized via ADMET [76, 77]. Acetal-containing dienes have undergone ADMET polymerization with Grubbs [Ru] 1 catalyst to yield the polymer in quantitative yield [78,53]. Additionally, dienes containing primary, secondary, and tertiary alcohols have been shown to be amenable to ADMET polymerization (Figure 13.7) [79]. 

Figure 13.7 ADMET polymerization of acetal and alcohol dienes.

By designing the repeat unit into the parent diene (containing either an alkyl branch or functionality), only a single type of repeat unit is formed upon polymerization, giving pure polymer microstructures. To date, perfectly controlled ADMET ethylene copolymers have included ethylene-CO,34 ethylene-vinyl alcohol,35 ethylene-vinyl acetate,36 and ethylene-propylene.20 Figure 8.12... 

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