Daughter polymer

Kammerer ei aL1(n m have conducted extensive studies on the template polymerization of acrylate or methacrylate derivatives of polyphenolic oligomers 22 with X n < 5 (Scheme 8.14). Under conditions of low "monomer" and high initiator concentration they found that X n for the daughter polymer was the same as X n for the parent. The possibility of using such templates to control microstructure was considered but not reported. 

A new form of template polymerization based on ring-opening polymerization of 4-methylcncdioxalane has been reported by Endo and coworkers (Scheme 8.15).220,221 For this system, the monomer is covalently bound and the daughter polymer is released from the template as a consequence of the polymerization process. 

Template or matrix polymerization can be defined as a method of polymer synthesis in which specific interactions between preformed macromolecule (template) and a growing chain are utilized. These interactions affect structure of the polymerization product (daughter polymer) and the kinetics of the process. The term template polymerization usually refers to one phase systems in which monomer, template, and the reaction product are soluble in the same solvent. 

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. 

The initial rate of polymerization versus base molar concentration ratio of template to monomer shows a sharp maximum in the range of [T]/[M] = 1.5. Polymerization was initiated by AIBN and UV light at 365 nm. Poly(dimethylaminoethyl methacrylate) with polyCacrylic acid) give a complex. During polymerization, precipitation takes place. From the product obtained, the daughter polymer and the template were isolated by dissolving the complex in 10% NaCl solution, addition of proper amount of NaOH, followed by dialysis. 

Many radical polymerization systems were examined hy Challa at a/. A number of papers were devoted to polymerization of methyl methacrylate, MM, in the presence of poly(methyl methacrylate). The role of tacticity of template was stressed. Isotactic PMM forms stereocomplex with syndiotactic PMM. Polymerizations of MM in the presence of isotactic PMM were carried out and the product (template + daughter polymer) was analyzed by NMR. When MM is polymerized in the polar solvent in the presence... 

The authors found that 4- and 2-vinylpyridines and N,N-dimethylaminostyrene polymerize spontaneously at 50°C in DMF or acetone in the presence of poly(maleic anhydride). Product obtained consist of 1 1 mixture of poly(vinylpyridine) and the template. Moreover, degree of polymerization of daughter polymer was almost the same as degree of polymerization of the template used. After separation of the polymerization product, it was found that for PVP, P = 14, whereas for poly(maleic anhydride) used as a template, Pn = 12. 

The described reaction is a very interesting case of template radical polymerization in which daughter polymer called by the authors of the article newborn polymer is not connected with the template by covalent bonds nor by hydrogen bridges. Separation the newborn polymer can be done without any operations such as hydrolysis or destruction of a polymeric complex. Examination of findings leads to the conclusion that in products of the described reaction, a small amount of graft copolymer exists. 

The presence of poly(vinylpyrrolidone) in the system increases substantially molecular weight of poly(L-leucine) obtained. If the ratio of template to monomer is 1.35, the molecular weight is more then 10 times higher than for the blank reaction. The influence of molecular weight of PVP template on the molecular weight of the daughter polymer was very significant as seen from the Table 6.4. 

Polymerization of L-leucine in the presence of PVP with molecular weight 1x10" gives polyleucine with M=1,000, while use of PVP with molecular weight 3.6x10 , leads to daughter polymer with M almost 35,000. Polycondensation of various amino acids hy the synthesis with triphenyl phosphite in the presence of PVP is presented in Table 6.5. 

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 ... 

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. 

A simple gravimetric method based on the precipitation and weighting of the dried product in the case of template polymerization is more complicated than in the case of common polymerization. Usually polymeric template precipitates with the daughter polymer and separation is difficult. For these reasons this method is not very often used. 

If a product of template polymerization is composed of a daughter polymer and a template involved in polymer complex, the first step of analysis is separation of these two parts. Separation of two polymers forming a complex is sometimes difficult and depends on interactions between the components. Very often polymeric complexes are insoluble in water and also in organic solvents. In order to dissolve such compounds, aqueous or non-aqueous solutions of inorganic salts such as LiBr, LiCl, NH4CNS are used. Dimethylformamide or dimethylacetamide are commonly used as non-aqueous solvents. If one of the components is a polyacid, alkali solutions are used as solvent. Ferguson and Shah reported that the complex obtained by polymerization of acrylic acid in... 

Another method of analysis of polymeric complexes is based on the separation of components by chemical reaction. Isolation of daughter polymer from polymeric complex obtained by template polymerization of methacrylic acid in the presence of poly(vi-... 

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. 

In the case of template polymerization, when reacting units are connected with the template by covalent bonds, analysis of the products can also be based on the separation of daughter polymer from the template. However, the covalent bonds should be broken for instance by hydrolysis of ester groups. This method was applied by Kammerer and Jung in order to prove that daughter polymer has the same number of units (plus end-groups) as the template. The scheme of the reaction can be represented as follows ... 

Fig. 6. Application of a linear template, T, directing the assembly of a daughter polymer...

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