Metal-polymer bond

The preparation of the surfaces being together is often decisive in adhesion. Therefore, in the following we will briefly discuss the effects of different gas phase treatments of polyolefins (mainly plasma and corona discharge) on the adhesion for three representative groups polymer polymer or polymer adhesive bonding, metal-polymer bonding, and polymer-matrix composites. 

The primary challenge facing adhesive bonding of metals is to obtain sufficient durability of a bonded structure. Initial bond strength in metal-polymer adhesive joints is almost invariably excellent. Challenging the application of adhesives in polymer-polymer joining, however, is the problem of obtaining a joint that is... 

Molecularly imprinted polymers (MIPs) can be prepared according to a number of approaches that are different in the way the template is linked to the functional monomer and subsequently to the polymeric binding sites (Fig. 6-1). Thus, the template can be linked and subsequently recognized by virtually any combination of cleavable covalent bonds, metal ion co-ordination or noncovalent bonds. The first example of molecular imprinting of organic network polymers introduced by Wulff was based on a covalent attachment strategy i.e. covalent monomer-template, covalent polymer-template [12]. 

However, in olefin polymerization by two-component catalysts during polymerization not only active transition metal-polymer bonds are formed, but also inactive aluminum-polymer ones, as a result of the transfer process with the participation of a co-catalyst (11, 162-164). The aluminum-polymer bonds are quenched by tritiated alcohol according to the scheme (25), so an additional tagging of the polymer occurs. The use of iodine (165, 166) as a quenching agent also results in decomposing inactive metal-polymer bonds. 

The experimental evidence for the availability of the coordinative insufficiency of the transition metal ion in the propagation centers was obtained (175) in the study of the deactivation of the propagation centers by coordination inhibitors. On the introduction of such inhibitors as phosphine and carbon monoxide into the polymerization medium, the reaction stops, but the metal-polymer bond is retained. It shows that in this case the interaction of the inhibitor with the propagation center follows the scheme ... 

Some experimental data on the lifetime of the active metal-polymer in one-component catalysts and the polarization of the active bond can be presented. 

The Mean Lifetime of the Active Metal-Polymer Bond... 

The mean lifetime of the active metal-polymer bond in one-component catalysts is limited by the following transfer processes (69, 76, 159) ... 

Olefin polymerization by catalysts based on transition metal halogenides is usually designated as coordinated anionic, after Natta (194). It is believed that the active metal-carbon bond in Ziegler-Natta catalysts is polarized following the type M+ - C. The polarization of the active metal-carbon bond should influence the route of its decomposition by some compounds ( polar-type inhibitors), e.g. by alcohols. When studying polymerization by Ziegler-Natta catalysts tritiated alcohols were used in many works to determine the number of metal-polymer bonds. However, as it was noted above (see Section IV), in two-component systems the polarization of the active bond cannot be judged by the results of the treatment of the system by alcohol, as the radioactivity of the polymer thus obtained results mainly from the decomposition of the aluminum-polymer bonds. 

The most frequently used organic supports are polystyrene and styrene-divinylbenzene copolymer beads with functional groups such as diphenylpho.sphine covalently bonded. The polymer-anchored catalyst complex can then be obtained, for example, by displacement of a ligand already co-ordinated to a soluble metal complex (Cornils and Herrmann, 1996) ... 

One way to overcome the problem of chirality existing only at the metal-matrix interface is to encase the metal particle inside the chiral matrix. In that case, all of the metal surface atoms should be close to a chiral center however, this approach has some problems too. For example, access to the metal surface may be inhibited by the encasing matrix. In spite of this, several attempts have produced moderately successful catalysts by creating metal—polymer catalysts. Pd has been deposited on poly-(5)-leucine (Scheme 3.4) and Pd and Pt colloids have been encased in a polysaccharide to produce catalysts that enanti-oselectively hydrogenated prochiral C=C and C=N bonds (Scheme 3.5).7... 

The previous section described the supramolecular side chain functionalization of polymers based on a single recognition motif. However, biological systems use a wide variety of noncovalent interactions such as hydrogen bonding, metal coordination, and hydrophobic interactions in an orthogonal fashion to introduce function,... 

When the radicals, coordinated with a catalyst, produce polymers, the catalyst is precipitated and inactivated by forming an inseparable bond with polymers, especially in a nonpolar solvent such as benzene. However, a polar solvent such as butyric acid or dimethyl sulfoxide is believed to expel the coordinated peroxy radical from the metal, thereby keeping it active during the reaction. 

Polymer-metal complexes often exhibit high efficiency in the catalytic decomposition of hydrogen peroxide. The following reasons for this activity have been advanced, (i) Some polymer-metal complexes contain incomplete complexes due to steric hindrance, and this contributes to their catalytic activity121, 122. (ii) In other polymer complexes, the coordinate bond between polymer ligand and metal ion is relatively weak and the substrate coordinates with high frequency124. ... 

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