Monomeric complexes methacrylates

When equal amounts of solutions of poly(ethylene oxide) and poly(acryhc acid) ate mixed, a precipitate, which appears to be an association product of the two polymers, forms immediately. This association reaction is influenced by hydrogen-ion concentration. Below ca pH 4, the complex precipitates from solution. Above ca pH 12, precipitation also occurs, but probably only poly(ethylene oxide) precipitates. If solution viscosity is used as an indication of the degree of association, it appears that association becomes mote pronounced as the pH is reduced toward a lower limit of about four. The highest yield of insoluble complex usually occurs at an equimolar ratio of ether and carboxyl groups. Studies of the poly(ethylene oxide)—poly(methacryhc acid) complexes indicate a stoichiometric ratio of three monomeric units of ethylene oxide for each methacrylic acid unit. 

Association Complexes. The unshared electron pairs of the ether oxygens, which give the polymer strong hydrogen bonding affinity, can also take part in association reactions with a variety of monomeric and polymeric electron acceptors (40,41). These include poly(acrylic acid), poly(methacrylic acid), copolymers of maleic and acrylic acids, tannic acid, naphtholic and phenolic compounds, as well as urea and thiourea (42—47). 

It was earlier reported that copolymerisation of HEMA, MAA and methacrylate-histidine coordinated with Co resulted in a copolymer in which the three monomers are so placed along the polymer chain that they could be again brought close to each other to form a complex with Co. Due to the different monomer reactivity ratios of the three monomers, such placement of monomers was not observed when copolymerisation was carried out in the absence of Co. This suggests that monomers bearing hydroxyl, carboxyl and imidazole groups, when coordinated with Co, undergo polymerisation as a monomeric Co(II) complex and do not form a random copolymer of the three monomers. 

The simple lithium tetraorganoaluminates including LiAlEt4 are known to polymerize methyl methacrylate monomers [222]. This is, however, only possible at the very low temperature of -78°C. In contrast, preformation of the i-Bu2Al(BHT)-t-BuLi complex, then treatment of methyl methacrylate at 0°C afforded PMMA with a molecular weight of 28400 (Scheme 6.174) [223]. NMR analysis revealed that the alkyl group bonded to the end of the polymer chain is the t-Bu moiety derived from t-BuLi and not alkyl groups from aluminum. The contribution of two enolate intermediates, monomeric and dimeric aluminum species, was invoked to account for the structure of the initiation species. 

The above examples show the complexity of the systems involving radical-anions derived from compounds of higher electron-affinity. It is not surprising, therefore, that benzophenone ketyl and other similar compounds do not initiate styrene polymerization, although they initiate polymerization of acrylonitrile or methyl-methacrylate. On the other hand, the monomeric dianions of benzophenone initiate polymerization of styrene as well as of other monomers, but not of vinyl chloride or acetate. Mechanisms of these initations were not investigated and presumably are complex. 

Titanium ester enolates are not only versatile reagents for asymmetric aldol additions but also function as starters of methacrylate polymerization. A representative titanium complex 24 was characterized by crystal structure and NMR spectroscopy and reveals the monomeric O-bound enolate character. The six-coordinated titanium atom in 24 is bound to two phenolic traws-oriented oxygen atoms and two sulfur donors the remaining ligands, methyl group, and enolate moiety are c/s-configured. Upon exposure to acetone, a spontaneous aldol occurs, and the aldolate 25 thus formed was also characterized by a crystal structure. Due to its coordinative saturation, the titanium obviously does not form a chelate with the carbonyl oxygen (Scheme 3.9) [57]. 

In a donor solvent such as methyl methacrylate, ligand exchange occurs at 25 C and monomeric and dimeric complexes such as (A) and (B) are produced [11] ... 

Cu(II)-polymer complexes initiate radical polymerization and often show higher activity than the corresponding monomeric analogues. The systems of Cu(II) ion with nylon [97], a-aminocaproic acid [96], nylon oligomers [96], polyethylene-polyamine [98,99], pt)ly(vinylamine-co-vinyl alcohol) [100], and cellulose have been made by Imoto and Takemoto as initiation systems for free radical polymerization of vinyl monomers, such as methyl methacrylate (MMA). Inaki et al. reported that Cu(II)-polyvinylamine complexes in the presence of CCI4 in an aqueous solution showed higher activity as an initiator than Cu(II)-diaminopropane complex for the radical polymerization of methyl methacrylate, acrylonitrile, and styrene [101]. The pH dependence for activity indicates that the free amine groups on the poly(vinylamine) chain are involved in the catalysis. The initiation mechanism is proposed as follows [Eqs. (78-80)] ... 

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