Examples of Template Polycondensation

Another example of template polycondensation was described by Ogata and co-workers (82-85). Polycondensation of dimethyl tartrate or dimethyl muconate with hexamethylenediamine was increased by the presence of poly(vinylpyrrolidinone) and poly(vinyl alcohol). It was also foimd that polysaccharides increase the polycondensation rate. It seems that hydroxyl groups play a substantial role in the absorption of monomers onto the template. 

For the preparation of nano- and microstructures there are numerous examples of endo- and exo-templates that have been used for the synthesis of particle- and pore structures from the nanometer to the micrometer scale. Templates can be inorganic, organic, or biological materials as are the materials or casts produced therefrom. The hardening process can be physical (crystallization from the melt, glass formation) or chemical (cross-linking, polycondensation). Templates usually have to be extracted in order to obtain the desired material. 

In thecfe novo synthesis the nucleoside triphosphates are polycondensed to polynucleotides under the influence of certain enzymes and in the absence of templates, primers and Mg " ions. One-strand homopolymers are produced by this method, for example, poly(dA) or poly(dG). The molar mass distribution corresponds to that of the most probable Schulz-Flory distribution. 

Another example is the template-assisted hydrolysis/polycondensation of precursors with a C=C bond in the unit that can be bonded to a metal centre like precursors 64 and 5593,101 -pjjg templating effect of palladium(II) compounds was readily demonstrated by the gelation time which is 100 times smaller for 64 when the Pd(II) compound is present. In contrast, the presence of the same palladium(II) compound has no effect on... 

The reactivity of butadiene and -diyne derivatives in layer perovskites demonstrates the suitability of these complex salts to act as templates for solid state reactions. Besides the polyaddition also other chemical reactions should be able to occur with a high stereoselectivity, as for example isomerizations, or addition reactions, such as hydrations, halogenations, oxidations, or polycondensations. In any case it will... 

A new type of polycondensation by means of phosphoms compounds in mild conditions was described by Higashi and co-workers and template effects were observed. The synthesis of polyamidation of polyamides by direct polyamidation of terephthalic acid with 4,4 -diaminodiphenylmethan was examined. P2VP, P4VP, poly(vinylpyrrolidone), and PEO were used as templates. For example, it was found that poly (terephthalamides) prepared from p-phenylenediamine and 4,4 -diaminodiphenylsulfone in the presence of PVP have much higher molecular weight than the same polymer obtained by a direct polycondensation reaction. 

A more reliable method to control the dimensions of hollow silica particles can be achieved using molecular assemblies, such as micelles and vesicles, as soft templates. For example, hollow silica particles of a controlled diameter (60-120 nm) were obtained using unilamellar vesicles consisting of mixtures of cationic and anionic surfactants [10]. The key point is that these vesicles are stable under the conditions for acid-catalyzed hydrolysis and polycondensation of... 

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