Template-guided polymerization

The inter-relationship between colloid and polymer chemistries is completed by colloidal polymer particles. The formation of 50-nm-diameter, 100- to 200-nm-long polyaniline fibrils in a poly(acrylic acid)-template-guided polymerization, similar in many ways to those produced from polymerized SUVs (see above), provides a recent example of polymer colloids [449], The use of poly(styenesulfonic acid) as a template yielded globular polyaniline particles which were found to be quite different morphologically from those observed in the regular chemical synthesis of polyaniline [449]. 

FIGURE 5.18 Template-guided polymerization to make water-soluble polyaniline (PanAquas). Aniline monomer is complexed to a polyacid template and then oxidatively polymerized inacontrolled fashion. (After Nguyen, M. T., Kasai, P., Miller, ). L., and Diaz, A. F. 1994. Macromolecules, 27, 3625.)... 

Protonic doping is necessary to convert PAN from an insulator to a conductor (136), and so various dopants such as acid-substituted polymers (143-146) and chiral sulfonic acids (147-149) have been employed. Emulsion polymerization of aniline-afforded PAN particles (150-156) and PAN-silica particles (157,158). Polyaniline nanofibers have been synthesized by template-guided polymerization... 

Fig. 32.11 Template-guided polymerization of water-soluble polyanilines (PanAquas). (1) Aniline monomer is complexed to a polyacid template (2) complex is oxidatively polymerized in a controlled fashion. (From Ref. 49.)...

All nucleic acids are usually synthesized by DNA template-guided polymerization of nucleotides— ribonucleotides for RNA and deoxy(ribo)nucleotides for DNA. The reactant monomers are 5 ribonucleoside (or deoxyri-bonucleoside) triphosphates. These can be described in the following chemical equations ... 

Early work on DNA polymerase I led to the definition of two central requirements for DNA polymerization. First, all DNA polymerases require a template. The polymerization reaction is guided by a template DNA strand according to the base-pairing rules predicted by Watson and Crick where a guanine is present in the template, a cytosine deoxynucleotide is added to the new strand, and so on. This was a particularly important discovery, not only because it provided a chemical basis for accurate semiconservative DNA replication but also because it represented the first example of the use of a template to guide a biosynthetic reaction. 

An elaboration of this technique, incorporating the concept of template-guided synthesis, is the use of nanoporous matrices such as zeolites and polycarbonates as a template within whole pores to perform the chemical polymerization of aniline monomers. For example, Wu and Bein254 have prepared nanofilaments of conducting PAn in the 3-nm-wide channels (pores) of the aluminosilicate host, MCM-41, through initial adsorption of aniline vapor into the dehydrated host followed by oxidation with (NH)2S208. 

J. M. Liu and S. C. Yang, Novel coUoidal polyanihne fibrils made by template guided chemical polymerization, J. Chem. Soc., Chem. Commun., 1529 1531 (1991). 

Polymer complexes of PANI and a polymeric dopant such as polyfacrylic acid) or poly (methylvinlyether-flZt-maleic add) have been synthesized using what the authors describe as a template-guided synthetic method to form aqueous solutions or dispersions of the complex [230]. An advantage of these polymer complexes is that they remain conductive at pH value up to 9, making them potentially usefiil in marine environments. The PANI complexes were used as additives (l%-5%) in a commercial waterborne epoxy, which was then applied to various A1 alloys (AA 2024-T3, AA 7075-T6, and AA 6061). The coatings were found effective in inhibiting corrosion of the A1 alloys in air-saturated seawater. 

Template-guided synthesis 2,4) is currently being used increasingly to synthesize water soluble polyaniline. Apofyadd is used as a tenq>late to bind the aniline monomers to form the corresponding anilinium salt. Aniline monomers polymerize to form a conq)lex with the template. The hydrophobic and hydrophilic ends of the tenq)late he in sohibifizing the hydrophobic polyaniline chains. Some of the pofyadds used (25) in the synthesis of polyaniline are polystyrenesulfonic add, poly(aci dic add) and poly(methacrylic acid). 

Template-guided synthesis Comparison of chemically and electrochemically prepared PAn films In situ chemical polymerization Deposition on glass/plastics... 

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