Template polymerization poly

Microstructure. Interest in PVP microstmcture and the potential for tacticity has been reviewed (39,40). PVP generated by free radicals has been shown to be atactic except when polymerization is conducted in water. In this case some syndiotacticity is observed (40). In the presence of syndiotactic templates of poly(methacryhc acid) (or poly(MAA)), VP will apparentiy polymerize with syndiotactic microstmcture, although proof is lacking (41—45). The reverse, polymerization of MAA in the presence of PVP, affords, as expected, atactic poly(MAA) (46,47). 

The authors found that the yield of 30-mer (a product with 5—6 linkages) was not much smaller than that of 10-mer or 12-mer. These facts indicate that the stability of the complex between the oligonucleotides and the complementary template is the most important factor in determining the extent of the condensation. The strong influences of template polymer (Poly C) are demonstrated in Fig. 9, in which the elution profile is shown of the polymerization products of (2 MeIp)6 in the presence of Poly C (B) and in their absence (A). 

Spontaneous polymerization of 4-vinyl pyridine in the presence of polyacids was one of the earliest cases of template polymerization studied. Vinyl pyridine polymerizes without an additional initiator in the presence of both low molecular weight acids and polyacids such as poly(acrylic acid), poly(methacrylic acid), polyCvinyl phosphonic acid), or poly(styrene sulfonic acid). The polyacids, in comparison with low molecular weight acids, support much higher initial rates of polymerization and lead to different kinetic equations. The authors suggested that the reaction was initiated by zwitterions. The chain reaction mechanism includes anion addition to activated double bonds of quaternary salt molecules of 4-vinylpyridine, then propagation in the activated center, and termination of the growing center by protonization. The proposed structure of the product, obtained in the case of poly(acrylic acid), used as a template is ... 

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). 

Tewari and Srivastava published the results on interaction between atactic polyCvinyl acetate) and poly(acrylonitrile), and poly(methyl methacrylate) and poly(methacrylic acid). On the basis of viscometric measurements of DMF solutions of mixtures of the pair of polymers mentioned above, the authors concluded that for all the systems examined complex formation occurs. This observation explains the results published earlier by the authors about template polymerization of acrylonitrile, methacrylic acid, and methyl methacrylate carried out in the presence of poly(vinyl acetate). It was found that polymerization of acrylonitrile in DMF in the presence of atactic poly(vinyl acetate) (mol. weight 47,900) takes place much faster than without poly(vinyl acetate), especially, when concentration of the monomer is equimolar to the concentration of template repeat units. The overall energy of activation was found to be 55.76 kJ/mol for template polymerization and 77.01 kJ/mol for polymerization in the absence of the template. 

The template polymerization of methacrylic acid at 60 C in DMF was studied with atactic poly(vinyl acetate) M =66,400 used as a template. The effect of template, monomer, and initiator (AIBN) concentration on the kinetics of polymerization was studied dilatometrically. Viscometric measurements showed that complexation between poly(vinyl acetate) and poly(methacrylic acid) was maximized when the template to polymer ratio was 1 1, and for the same ratio of the monomer to the template, the rate of template polymerization also reached the maximum. The overall energy of activation was the same (115 kJ/mol) in the presence and absence of the template. The polymerization follows mechanism II ( pick up mechanism ). 

Very interesting method of template polymerization was proposed by Japanese scientists. The method is based on the charge transfer interaction between template and monomer. In the course of the studies on the interaction of poly(maleic anhydride) with organic amines, the authors found strong charge transfer interaction of pyridines with poly(maleic anhydride). The polymer with pyridine gives brown-colored system with the absorption maximum at 480 nm. 

In radical template polymerization, when only weak interaction exists between monomer and template and pick-up mechanism is commonly accepted, the reaction partially proceeds outside the template. If macroradical terminates by recombination with another macroradical or primary radical, some macromolecules are produced without any contact with the template. In fact, such process can be treated as a secondary reaction. Another very common process - chain transfer - proceeds simultaneously with many template polymerizations. As a result of chain transfer to polymer (both daughter and template) branched polymers appear in the product. The existence of such secondary reactions is indicated by the difficulty in separating the daughter polymer from the template as described in many papers. For instance, template polymerization of N-4-vi-nyl pyridine is followed, according to Kabanov et aZ., by the reaction of poly(4-vinylpyridine) with proper ions. The reaction leads to the branched structure of the product ... 

In contrast, similar examination of the product obtained by template polymerization of acrylic acid on poly(ethylene imine), using electrophoresis, leads to the conclusion that in this case graft copolymer is absent. 

Application of classical type of kinetic equations to the template polymerization was demonstrated by Kabanov at al It was shown that 4-vinylpyridine, in the presence of poly(methacrylic acid), poly(acrylic acid), poly(l-glutamic acid), and polyphosphate, polymerizes according to the classical equation and the order of reaction with respect to the monomer is 2 as demonstrated in the Figure 8.1. In log-log coordinates, for the all sets of polymerizations, experimental points fit straight lines. In the same paper dependence of the initial rate on the molar ratio of acid to monomer was examined. This relationship is shown on the Figure 8.2. The rate of polymerization in the presence of the poly(acrylic acid) is much higher than that for the low molecular analogue (acetic acid). The polymerization rate riches its maximum for the molar ratio [acid]/[monomer] 2. The authors found kinetic equation for template polymerization of 4-vinylpyridine in the presence of different polyacids in the form ... 

Figure 8.6. Template polymerization of AA along poly(N-vmylp)rridine) as a function of [T]o/[M]o at constant [M]o = 0.06 mol.dcm in methanol at 60°C. (o) Data from Fujimori The ciuves...

Indeed, it was observed that ov is lower for template polymerization (ASqv.t) than for blank reaction (ASov b)- Investigating polymerization of methyl methacrylate, in the presence of isotactic poly(methyl methacrylate), Gons et al. found that there is a difference in entropy of about 84 J mol" K" between template polymerization and the blank reaction. A similar value (90-100 J mol IC ) was found by Lohmeyer et al It is more likely that the decrease of AS originates predominantly in the propagation process. 

Aleksina et al. investigating polymerization of methacrylic acid in the presence of poly-L-lysine found that the complex obtained by template polymerization has a 1 1 stoichiometry, while the same components obtained by separation of the complex and repeated mixing gave a complex in which the ratio of polylysine units to polyacid units is 2 3. The stable conformation of polylysine macromolecule in the complex obtained by template polymerization is the conformation of a-helix. 

Production of materials in which the daughter polymer and the template together form a final product seems to be the most promising application of template polymerization because the template synthesis of polymers requiring further separation of the product from the template is not acceptable for industry at the present stage. Possible method of production of commonly known polymers by template polymerization can be based on a template covalently bonded to a support and used as a stationary phase in columns. Preparation of such columns with isotactic poly(methyl methacrylate) covalently bonded to the microparticulate silica was suggested by Schomaker. The template process can be applied in order to produce a set of new materials having ladder-type structure, properties of which are not yet well known. A similar method can be applied to synthesis of copolymers with unconventional structure. 

The polycomplexes obtained by template polymerization of methacrylic acid or acrylic acid in the presence of poly(N,N,N, N - tetramethyl-N-p-xylene-ethylenediammonium dichloride) were used for spinning of fine fibers 5 to 50 pm in diameter. The fibers are soluble in water but become stable after thermal treatment at about 80°C. The polycomplex with regular structure, obtained by template polymerization, is expected to be of considerable interest for textile industry. 

As reported, by polycondensation of dicarboxylic acids with diamines or by polycondensation of aminoacids in the presence of polyvinylpyrrolidone, polymers with very high molecular weight were obtained. The viscosities of poly(terephthalamides) prepared by template polymerization in the presence of polyvinylpyrrolidone from p-phenylenediamine and 4,4 -diaminodiphenylosulfone and of poly(m-benzamid) are very high. Also, polypeptides with molecular weight of 20-30 thousands were obtained by template polymerization in the presence of polyvinylpyrrolidone ... 

The total concentration of complex formed during the complexation is proportional to X. During template polymerization of acrylic acid, a stable colloidal precipitate resulted in the systems under investigation, and turbidity measurements could be used, assuming that direct reading from the turbidimeter (in logarithmic scale) is proportional to the amount of polymeric product. The assumption was checked by calibration procedure. The light absorption (%) is proportional to the concentration of poly(acrylic acid)-poly(vinyl pyrrolidone) mixture.100% conversion was assumed when no increase in turbidity was detected by the recorder. In the case when copolymers were used as templates, the apparatus was calibrated for each copolymers separately. 

Paper chromatography was also used to separate the complex obtained by polymerization of acrylic acid in the presence of poly(ethylene imine). In this case, both the complex obtained by mixing of two polymers and the complex obtained in template polymerization gave two distinct spots. No trace was found of any graft copolymer. 

A similar procedure was described by Eboatu and Ferguson. An object of analysis was the complex obtained by template polymerization of acrylic acid in the presence of poly(vinyl pyrrolidone). The polycomplex was dispersed in dry benzene and treated with diazomethane. The insoluble portion was filtered. The filtrate containing poly(methyl acrylate) was concentrated and finally dried. The insoluble fraction was scrubbed with methanol to extract polyCvinyl pyrrolidone). The residue was further washed with methanol and then dried. These three portions were characterized by IR spectroscopy. It was found that only about 70% separation of the complex is achieved. The occurrence of inseparable portion is attributed to a graft copolymer formation. For the separated... 

Another complex obtained by template polymerization of dimethylaminoethyl methacrylate in the presence of polyCacrylic acid) was synthesized and analyzed by Abd-Ellatif. The procedure of separation was as follows to the complex dissolved in 10% NaCl solution, 10% NaOH solution was added dropwise and white gel was precipitated. Addition of sodium hydroxide was continued until no more precipitate was separated. The soluble polymer after dialysis was dried and identified as poly(acrylic acid). The insoluble polymer fraction was found to be insoluble in toluene, benzene, tetrahydrofurane, but soluble in acetone/water (2 1 v/v). Elemental analysis and IR spectra lead to the conclusion that this fraction consists of pure poly(dimethyl aminoethyl methacrylate) which was expected as a daughter polymer. 

The first result is that pyrimidine nucleosides do not give template polymerizations under the conditions tried. This is attributed to the inability of pyrimidine nucleosides to stack on the poly A or poly G template. It is possible that early template polymerizations used dimers, trimers, etc. which may stack, or that there may be conditions not yet found which... 

The template polymerization of MAOT in the presence of stereoregular poly-MAOA was never accelerated. A strong tendency to cause self-association of adenine bases observed along the polyMAOA chain32) as well as in poly-VAd17,24) appears to inhibit the complex formation between a growing chain and polyMAOA and may result in a depression of the template effect of the polymerization. 

Xiao et al. investigated the electrochemical synthetic mechanism of conducting-polymer nanotubes in a porous alumina template using poly(3,4-ethylenedioxythiophaie) (PEDOT) as a model compound [70]. The electrochemical polymerization of EDOT was performed potentiostatically at various potentials from 1.0 to 1.8 V (vs. Ag/AgCl) in a solution containing EDOT, LiC104, and acetonitrile. They found that the tubular portion of the nanotube structure increased as the applied potential increased from 1.4 to 1.8 V at a fixed concentration of EDOT, while the tubular portion decreased with increasing monomer concentration from 10 to 100 mM at a fixed poteitial of 1.6 V. 

There were attempts at controlling steric placement by a technique called template polymerization. An example is methyl methacrylate polymerization in the presence of isotactic poly(methyl methacrylate). The presence of template polymers, however, only results in accelerating the rates of polymerizations. 

An alternative strategy toward the formation of such inclusion complexes, reported by Kadokawa et al., is to use the enzymatic polymerization of glucose on a template polymer, where phosphorylase catalyzes a polymerization reaction of a-D-glucose 1-phosphate monomer along the template polymer [poly(tetrahydrofuran)] in a twisting manner [17]. The same inclusion complex was not formed upon just mixing natural amylose with polymer [poly(tetrahydrofuran)], probably due to the rigid conformation of natural amylose. 

Ethylenedioxythiophene and sutfonated poly (amic acid) can be polymerized via template polymerization at more than 150 °C to give a stable conducting polymer aqueous dispersion with a particle of 63 nm [53,54]. 

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