Polymerization conditions vinylpyrrolidone

One half of an aqueous solution of vinylpyrrolidone (VP) is added to the reactor while the other half is added in portions during the polymerization. The polymerization is initiated when hydrogen peroxide and ammonia are added to the reaction mixture. The ammonia serves as a buffer in the solution in order to provide an alkaline condition, thus preventing the splitting off of the acetaldehyde from the monomer during the reaction. The rate of the peroxide-initiated polymerization is expressed as ... 

Acrylamide, 2-methyl-5-vinylpyridine and /V-vinylpyrrolidone can be polymerized under similar conditions, and also after decomposition of a monomer-peroxide complex. On the other hand, styrene, methyl methacrylate, isoprene, methyl acrylate, vinyl acetate and ascorbic acid do not polymerize under these conditions. Complex formation between persulphate and these monomer donors is more favourable energetically [165]. The complex is more stable, it is not decomposed into initiating radicals and polymerization does not occur. 

Mohammad et al. [29] fabricated NF composite membranes by the interfacial polymerization technique and studied the membrane s surface by AFM. The membrane support was prepared from a dope containing polysulfone (PSf) (P1835-BP Amoco) and poly(vinylpyrrolidone) (PVP) (Fluka) with JV-methyl-2-pyrrolidone (NMP) as the solvent. The top active layer was obtained through interfacial polymerization between trimesoyl chloride (TMC) in hexane and the aqueous phase containing bisphenol A (BPA). Table 5.9 shows the summary of the membrane preparation conditions. The first three membranes identified as PT-30, PT-45, and PT-60 differ in the period of interfacial reaction. The other three membranes identified as PC-05, PC-1, and PC-2 differ in terms of the concentration of BPA in the aqueous phase. The pore sizes determined by AFM and also calculated using the Donnan-steric-... 

The thiacrown ether monomers (15) were polymerized and copolymerized with styrene [100-42-5] and A -vinyl-2-pyrrolidinone (AT-vinyl-2-pyrrolidone, N-vinylpyrrolidone, l-vinyl-2-pyrrolidone, l-vinyl-2-pyrrolidinone, vinylbutyrolac-tam, etc) [88-12-0] by radical polymerization, giving the thiacrown ether pol3uner ligands which had binding selectivity for Ag(I) and Hg(II) ions. These polymers are likely to be efficient sorbents for the heavy metal ions imder industrial conditions, since they can be used repeatedly under acidic conditions (15,16). 

Sakaguchi et al. also investigated the free-radical polymerization of several monomers in the presence of poly(iV-vinylpyrrolidone) and reported that meth-acrylic acid under these conditions yields the isotactic polymer. This observation appears to conflict with conclusions of Challa et al. (see Section 4). 

A more recent development is template polymerization [520 522]. When acrylic acid was polymerized in aqueous solution using potassium persulfate as initiator, the polymerization proceeded very slowly. In the presence of poly(vinylpyrrolidone) but under otherwise identical reaction conditions, the rate of polymerization increased dramatically, depending on the amount of PVP. At nearly equimolar concentrations of PVP and monomer, the rate of polymerization reaches a maximum value, because of the strong interaction between poly(vinylpyrrolidone) and acrylic acid in aqueous solution (Scheme 40) [523]. 

A review article by Fikentscher and Herrle [1] discusses the solution polymerization of this monomer in considerable detail. This material is summarized here so that readers may develop their own reaction procedures on the basis of the information. The reaction conditions based on this work are reliable for the preparation of copolymers of N-vinylpyrrolidone and vinyl acetate [47]. 

The concentration N-vinylpyrrolidone has an effect on the rate of polymerization and the induction period. With increasing monomer concentration, the rate increases up to approximately 30%, then remains constant up to approximately 60%. Beyond this concentration, it decreases sharply. Pure N-vinylpyrrolidone does not seem to polymerize under these reaction conditions. 

By substituting in the polymerization process a part of aminic monomers for allylamine, linear poly(amido-amines) having pendant allylic groups were obtained. Subsequently, these poly(amido-amines) were treated with a hydrophilic monomer (vinylpyrrolidone), in the presence of radical initiators. Crosslinked products in which the poly(amido-amine) chains were connected by polyvinylpyrrolidone chains, were finally obtained (Scheme 3). The reaction condition could be adjusted to have about 50% by weight of poly(amido-amine) chains in the final products (21). 

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