Polycondensation heterogeneous

Pol5uireas were among the first polycondensation pol-5mers to be employed as catal dic supports for heterogeneous metal catalysts. The first report about palladium on polyurea, by Zhang and Neckers [99] dates back to 1979. They obtained their catalyst in a two step preparation, where the co-monomers (2,4- toluendiisocyanate, TDI, and the complex between palladium acetate and 4,4 -di-amino-2,2 -bip5Tiridine) were condensed together and... 

Polycarbonates have also been studied recently with regard to chemical heterogeneity. Polycarbonates are polycondensation products of phosgene and aliphatic or aromatic dihydroxy compounds. 

In Chap. C we have discussed in some detail the application of the cascade theory to polycondensates in their unperturbed state. In Chap. D some experimental results were already given for cross-linked or vulcanisated linear chains. In this chapter we shall now outline in brief how cross-linking chain reactions or the vulcanization of preformed chains of an arbitrary length distribution can be treated by cascade theory. Second, we shall discuss how heterogeneities in branching or a rigidity of a certain domain can be taken into account. 

The sol-gel method was applied for the preparation of heterogenized complexes such as Structure 3 based on the polycondensation of suitable trialkoxy-silyl-substituted organosulphides, organophosphines, and organoamines bound as ligands to a given complex (Pt, Rh, Ir, Ru). They were employed in the hydrosilylation of allyl chloride and other olefins [88]. 

It was found meanwhile that nearly every slim unbranched polymer chain, such as poly(trimethylene oxide) [224], poly(l,3-dioxolane) [225], poly(tetramethylene oxide) [226], polyethylene imine) [227], poly(3-hydroxy propionate), poly (4-hydroxybutyrate) and poly(6-hydroxyhexanoate) [228,229], poly(butylene succinate) [229], polyadipates [230], nylon-6 [231], and even oligomers of polyethylene [232], form a-CD ICs with channel structures. In all of these cases, inclusion is a heterogeneous process, since the guest polymer and its CD complex are almost insoluble in water. Therefore, extensive sonication had to be applied to accelerate the diffusion process. The polymer was also dissolved in an organic solvent, e.g., nylon-6 in formic acid, and this solution was added to the solution of a-CD [231], Alternatively, a monomer, such as 11-aminoundecanoic acid, was included in a-CD and polymerized to nylon-11 by solid state polycondensation within the channels of the IC. Thus, the IC of nylon-11 was formed under conservation of the crystal packing [233-235],... 

Various methods for anchoring Gp titanium derivatives onto organic or inorganic supports have been developed. Heterogeneous epoxidation catalysts have been prepared by the co-polycondensation of Cp2TiCl2 and (CpTiCl2)20 with tetraethoxysilane by a modified sol-gel procedure, and the use in epoxidations of non-activated olefins have been described.1936... 

The polycondensation of amino acids was affected significantly by the solvent. Interestingly, nonpolar solvents (such as n-hexane) and haloalkanes (such as chloroform) gave polymers of relatively higher viscosity than highly polar aprotic solvents (such as DMF) in spite of heterogeneity of the system in these nonpolar solvents. 

The actual process of growth involves the building up of substances such as proteins, polysaccharides, and nucleic acids, aU of which are macromolecular compounds formed by reactions of polymerization and polycondensation. Reactions of this type are not unfamiliar in the inanimate world. They usually involve radical chains, and sometimes they are heterogeneous. In the formation of ethylene polymer... 

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