Template polymerization oxidation

The most examined monomers for template polymerization have been either acrylic or methacrylic acids. This is probably because many polymers, such as poly(ethylene oxide), PEG, and poly(vinyl pyrrolidone), PVP, form complexes with poly(acrylic acid). 

Ferguson and Shah described polymerization of AA in the presence of polyCethylene oxide), PEG, having mol. weight of 1,500 and 6,000. Polymerizations were carried out in water at 55 and 74°C. Potassium persulphate was used as an initiator. Having examined the influence of template concentration on the rate of polymerization, it was found that the maximum rate appears not at equimolar ratio of monomer to template, but at much lower concentration of the template. Polymerization of AA in the presence of PEG in water at 74°C was treated by the authors as an example of the system in which the interaction between template and the monomer is rather weak. Indeed, only tern-... 

Secondary reactions usually proceed in addition to template polymerization of the system template-monomer-solvent. They influence both kinetics of the reaction and the structure of the reaction products. Depending on the basic mechanism of reaction, typical groups of secondary reactions can take place. For instance, in polycondensation, there are such well known reactions as cyclization, decarboxylation, dehydratation, oxidation, hydrolysis, etc. In radical polymerization, usually, in addition to the main elementary processes (initiation, propagation and termination), we have the usual chain transfer to the monomer or to the solvent which change the molecular weight of the product obtained. Also, chain transfer to the polymer leads to the branched polymer. 

P.-C. Wang, E. C. Venancio, D. M. Sarno, and A. G. MacDiarmid, Simplifying the reaction system for the preparation of polyaniline nanofibers Re-examination of template-free oxidative chemical polymerization of aniline in conventional low-pH acidic aqueous media. React. Funct. Polym., 69, 217-223 (2009). 

The only example dealing with the template polymerization of simple monomers in the presence of two sorts of templates was described by Papisov et al. Polymerization of MAA in the presence of a mixture of poly (ethylene oxide) (PEO) and poly (N-vinylpyrrolidone) of sufficient chain lengths was examined. It was found that the rate of polymerization is determined by the template forming the stronger complex with a daughter polymer. 

Synthesis of hollow metal oxide nanospheres by templating polymeric micelles with core-shell-corona architecture. Inorg, Chem., 48,... 

An interesting example of a template polymerization was provided by Wu et al. [146]. Surfaces of Si02/Si substrates were first modified with a silane compound bearing pendant aniline groups via molecular self-assembly. This modified surface was then contacted with additional aniline monomer in the presence of the oxidant ammonium peroxydisulfate. The resulting CP films were claimed to be highly ordered with good substrate adhesion and conductivities for 1 /tm thick films were found to be 0.5 S/cm. 

According to Ref. [12], template for synthesis of nanomaterials is defined as a central structure within which a network forms in such a way that removal of this template creates a filled cavity with morphological or stereochemical features related to those of the template. The template synthesis was applied for preparation of various nanostructures inside different three-dimensional nanoporous structures. Chemically, these materials are presented by polymers, metals, oxides, carbides and other substances. Synthetic methods include electrochemical deposition, electroless deposition, chemical polymerization, sol-gel deposition and chemical vapor deposition. These works were reviewed in Refs. [12,20]. An essential feature of this... 

Martin and coworkers tried to prepare carbon tubes from the carbonization of polyacrylonitrile (PAN) in the channels of anodic oxide film (10). A commercially available film with a pore diameter of 260 nm was immersed in an aqueous acrylonitrile solution. After adding initiators, the polymerization was carried out at acidic conditions under N2 flow at 40°C. The PAN formed during the reaction was deposited both on the pore walls and on both sides of the film. Then the Film was taken from the polymerization bath, followed by polishing both faces of the film to remove the PAN deposited on the faces. The resultant PAN/alumina composite film was heat-treated at 250°C in air, and then it was heat-treated at 600°C under Ar flow for 30 min to carbonize the PAN. Finally, this sample was repeatedly rinsed in I M NaOH solution for the dissolution of the alumina film. The SEM observation of this sample indicated the formation of carbon tubes with about 50 xm long, which corresponds to the thickness of the template film. The inner structure of these tubes was not clear because TEM observation was not done. The authors claim that it is possible to control the wall thickness of the tubes with varying the polymerization period. 

---