Template Polycondensation

In this case one monomer with groups x (e.g., COOH) can he ahsorhed on the template -T-T-. The second monomer with groups y (e.g., amine) reacts, forming a daughter polymer having groups xy and the template is available for further reaction. Low molecular weight product is not indicated in this scheme. 

Mathematical description of the polymerization of biological macromolecules on templates, based on simple models, has been published by Simhaet al Two types of reaction were discussed. The first type of reaction was initiated by polymerization of two monomers on each template. The reaction proceeded throughout the addition of monomer to the growing ends or by the coupling of the growing chains. In the second type of re- 

Experimental investigation of the kinetics of template step polymerization, determination of average molecular weights of the product, and molecular weight distribution are still available for future studies. 

---

The template processes can be realized as template polycondensation, polyaddition, ring-opening polymerization, and ionic or radical polymerization. These types of template polymerization are fundamentally treated in the separate chapters below. 

Because template polycondensation is not very well studied at present/ general mechanism is difficult to present. Two main types of polycondensation are well known in the case of conventional polycondensation. They are heteropolycondensation and homopolycondensation. In the heteropolycondensation two different monomers take part in the reaction (e.g., dicarboxylic acid and diamine). In the case of homopolycondensation, one type of monomer molecule is present in the reacting system (e.g., aminoacid). The results published on the template heteropolycondensation indicate that monomer (dicarboxylic acid) is incorporated into a structure of the matrix (prepared from N-phosphonium salt of poly-4-vinyl pyridine) and then the second monomer (diamine) can react with so activated molecules of the first monomer. The mechanism can be represented as in Figure 2.2. 

There is far less information in the scientific literature about template copolymerization than about template homopolymerization. As in the case of template homopolymerization, template copolymerization can be realized according to different types of reaction stepwise (template polycondensation), copolyaddition, radical or ionic polymerization, ring-opening copolymerization, etc. 

In contrast to template polycondensation or ring-opening polymerization, template radical polymerization kinetics has been a subject of many papers. Tan and Challa proposed to use the relationship between polymerization rate and concentration of monomer or template as a criterion for distinguishing between Type I and Type II template polymerization. The most popular method is to examine the initial rate or relative rate, Rr, as a function of base mole concentration of the template, [T], at a constant monomer concentration, [M]. For Type I, when strong interactions exist between the monomer and the template, Rr vs. [T] shows a maximum at [T] = [M]q. For type II, Rr increases with [T] to the critical concentration of the template c (the concentration in which template macromolecules start to overlap with each other), and then R is stable, c (concentration in mols per volume) depends on the molecular weight of the template. 

Special type of template polycondensation product was obtained by Papisov at al Polycondensation of urea with formaldehyde in the presence of polyCacrylic acid) gives polycomplexes or polycomplex composites with various structures and properties. The... 

Properties of composites obtained by template poly condensation of urea and formaldehyde in the presence of poly(acrylic acid) were described by Papisov et al. Products of template polycondensation obtained for 1 1 ratio of template to monomers are typical glasses, but elastic deformation up to 50% at 90°C is quite remarkable. This behavior is quite different from composites polyacrylic acid-urea-formaldehyde polymer obtained by conventional methods. Introduction of polyacrylic acid to the reacting system of urea-formaldehyde, even in a very small quantity (2-5%) leads to fibrilization of the product structure. Materials obtained have a high compressive strength (30-100 kg/cm ). Further polycondensation of the excess of urea and formaldehyde results in fibrillar structure composites. Structure and properties of such composites can be widely varied by changes in initial composition and reaction conditions. 

PDMS has also been cured using UV (ultraviolet) radiation, " " gamma or electron beams, ° and laser irradiation. Thermal cures are also available. i 2-iss Iso relevant here are physically cross-linked fluo-rosilicone elastomers obtained by self-assembly and template polycondensation of tailored building blocks. ... 

Longuet, C. Ratsimihety, A. Andre, S. Boutevin, G. Guida-Pietrasanta, F. Deschamps, B. Ramonda, M. Joly-Duhamel, C. Boutevin, B. Ganachaud, F., Physically Crosslinked Fluorosilicone Elastomers Obtained by Self-Assembly and Template Polycondensation of Tailored Building blocks. J. Mater. Chem. 2010, 20,10269-10276. 

Template polycondensation or template polyaddition is much less elaborated than the chain template reaction. However, many cases of homo- and heteropolycondensation have been considered (11). 

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. 

A template polycondensation of urea with formaldehyde in the presence of acrylic acid was pnblished by Papisov and co-workers (88-92). The authors suggest that a complex with poly acid is formed during the reaction. The complex has a different structure than does urea—formaldehyde resin mixed with poly(aciylic acid). The reaction can he written as follows ... 

The quite remarkable properties of composites obtained by template polycondensation of urea and formaldehyde are described by Papisov and co-workers (92). The structure and properties of such composites can be widely varied by changing initial composition and reacting conditions. 

Synthesis.—A number of interesting developments in synthetic techniques have taken place recently. The use of template polymerization has up to now been confined to vinyl polymerization and the preparation of polypeptides from the A-carboxyanhydrides of amino-acids. The template polycondensation of active esters containing nucleic acid bases with diamines has been reported. The enantioselective ester synthesis in the presence of optically active polymers, a not dissimilar process to template polymerization, has also been reported. ... 

Template polycondensation of such monomers in the presence of P2VP and poly(4-vinylpyridine) (P4VP), poly (vinylpyrrolidone), poly(vinyl alcohol), and others was described. " The most interesting results obtained were by examining the template polycondensation of two monomers diethyl tartrate (A) and dimethyl mucate (B) or diethyl mucate (DEM). 

This type of template polycondensation was applied to the preparation of polypeptides directly from free amino acids. It was fotmd, for instance, that an increase in the amotmt of PVP template in polycondensation of r-leudne lead to the increase of molecular weight of polyleudne obtained. Also, increasing the molecular weight of the template from 1 x fO to 3.6 x 10 increased the obtained molecular weight of polyleudne more than 30 times. 

Properties of composites obtained by template polycondensation of urea and formaldehyde in the presence of PAA were described by Papisov et al. 

---