Alcohols ADMET polymerization

However, the regio-random distribution of functional groups can be avoided by an acyclic diene metathesis (ADMET) polymerization technique using symmetric monomers (33). The molecular weights of these polymers are restricted to < 3 x 104 Dalton by ADMET. Due to their rich hydrocarbon content, the barrier properties in final ethylene vinyl alcohol copolymers are reduced. 

More industrial polyethylene copolymers were modeled using the same method of ADMET polymerization followed by hydrogenation using catalyst residue. Copolymers of ethylene-styrene, ethylene-vinyl chloride, and ethylene-acrylate were prepared to examine the effect of incorporation of available vinyl monomer feed stocks into polyethylene [81]. Previously prepared ADMET model copolymers include ethylene-co-carbon monoxide, ethylene-co-carbon dioxide, and ethylene-co-vinyl alcohol [82,83]. In most cases,these copolymers are unattainable by traditional chain polymerization chemistry, but a recent report has revealed a highly active Ni catalyst that can successfully copolymerize ethylene with some functionalized monomers [84]. Although catalyst advances are proving more and more useful in novel polymer synthesis, poor structure control and reactivity ratio considerations are still problematic in chain polymerization chemistry. 

ADMET polymerization of dienes containing functional groups has been explored to some extent. It appears that diene ethers such as 36 are tolerant of Schrock s W-alkylidene catalysts when undergoing ADMET polymerization, but Grubbs first-generation catalyst is required to successfully polymerize diene alcohol 37,61 because the OH group is too Lewis basic for catalysis by W- and Mo-alkylidenes.62... 

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.

Amorphous, hydrophobic telechelic diols, which may be used in hydrolysis-and UV-resistant polyurethanes, have also been synthesized by ADMET [181]. ADMET polymerization and subsequent hydrogenation of a ew-dimethyl substituted a,m-diene produced the hydrocarbon backbone, which was end-capped by chain termination reactants having a varied number of methylene units between their olefin and alcohol precursor group. This resulted in 2.0 functional telechelics with good molecular weight control. 

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... 

The ruthenium catalyst system, 14, shown in Fig. 3, also carries out ADMET condensation chemistry, albeit with higher concentrations being required to achieve reasonable reaction rates [32]. The possibility of intramolecular compl-exation with this catalyst influences the polymerization reaction, but nonetheless, ruthenium catalysis has proved to be a valuable contributor to overall condensation metathesis chemistry. Equally significant, these catalysts are tolerant to the presence of alcohol functionality [33] and are relatively easy to synthesize. For these reasons, ruthenium catalysis continues to be important in both ADMET and ring closing metathesis chemistry. 

The mapping shown in Fig. 1 includes references to SBR and styrene block copolymers in the PB search. Removing these citations from the database reduced the number to 4297, which can be seen mapped in Fig. 3. the area of high activity is centered on hydroxy terminated PB (HTPB). Low-Mn HTPB can be prepared by a variety of polymerization processes such as radical, anionic, or even using acyclic diene metathesis (ADMET).f The HTPB has a variety of uses as a propellant. " Other uses include reaction with epoxy resins, nylon, urethane, or even in the formulation of adhesives.t" The use of HTPB as an oxygen scavenger in polyamide, polyvinyl alcohol, and multilayer... 

In the case of polyesterification, the condensate is water or an alcohol, which are somewhat more difficult substances to remove from the reaction. Removal of ethylene may be accomplished by applying vacuum to the reaction mixture or by passing an inert carrier gas over the reaction, although moderately high molecular weights can be achieved at room pressure without active removal of ethylene. For these reasons, high DP is attainable via ADMET, as demonstrated by a reported DP of almost 830 for the polymerization of 1,9-decadiene by a tungsten-based catalyst [31]. 

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