Monomer polymerizability

In this section, we consider the kinetics of propagation and the features of the propagating radical (Pn ) and the monomer (M) structure that render the monomer polymerizable by radical homopolymerization (Section 4.5.1). The reactivities of monomers towards initiator-derived species (Section 3.3) and in copolymerizalion (Chapter 6) arc considered elsewhere. 

Poly(azophenylene-o-carborane) (see 6) has been prepared from diphenyl-o-carborane by means of nitration, reduction, and acylation to initially give 1,2-bis(/ -nitroso-acetylaminophenyl)-o-carborane (NAFC). Rapid decomposition in solution affords phenylene amino phenyl carborane (PAFC) by recombination of phenylene and azophenylene radicals.40 These radicals have also been utilized to form copolymers of carborane-containing copolymers from monomers polymerizable via radical mechanisms. Thus, copolymers of polystyrene and poly(azophenylene) can be readily formed by means of emulsion copolymerization of styrene with NAFC decomposition products. 

Mecerreyes D, Humes J, Miller RD, Hedrick JL, Lecomte Ph, Detrembleur C, Jerome R (2000) First example of an unsymmetrical difunctional monomer polymerizable by two living/controlled methods. Macromol Rapid Commun 21 779-784... 

Table 6 Examples of the monomers polymerizable with Rh catalysts...

Typical hydrocarbon monomers polymerizable by using an alkyllithium initiator are... 

Cationic polymerizations induced by thermally and photochemically latent N-benzyl and IV-alkoxy pyridinium salts, respectively, are reviewed. IV-Benzyl pyridinium salts with a wide range of substituents of phenyl, benzylic carbon and pyridine moiety act as thermally latent catalysts to initiate the cationic polymerization of various monomers. Their initiation activities were evaluated with the emphasis on the structure-activity relationship. The mechanisms of photoinitiation by direct and indirect sensitization of IV-alkoxy pyridinium salts are presented. The indirect action can be based on electron transfer reactions between pyridinium salt and (a) photochemically generated free radicals, (b) photoexcited sensitizer, and (c) electron rich compounds in the photoexcited charge transfer complexes. IV-Alkoxy pyridinium salts also participate in ascorbate assisted redox reactions to generate reactive species capable of initiating cationic polymerization. The application of pyridinium salts to the synthesis of block copolymers of monomers polymerizable with different mechanisms are described. 

Table 5 demonstrates that substitution in the ring decreases monomer polymerizability because the intramolecular interactions between substituents are always higher in the polymer than in the cyclic monomer. Thus,... 

Monomers Polymerizable by Plasma Initiation. Polymerization data for all of the vinyl monomers utilized in this study are summarized in Table 1. As shown previously, methyl methacrylate is readily polymerizable (, ). Methacrylic acid (MAA) and acrylic acid (AA) are polymerized immediately upon exposure to the plasma. Because the resulting polymers are insoluble in their monomers, the products are precipitated out and conversion is low despite prolonged post-polymerization. However, if water is now added as solvent, polymerization becomes homogeneous and high conversions can be readily achieved with post-polymerization. For example, after a 15 second plasma initiation period more than 80% yield was obtained for a 75% aqueous solution of MAA. The molecular weight, determined by intrinsic viscosity measurements, was found to be 4.5 X 10 gm/mole. 

Clearly, this technique can be extended to Include other monomers polymerizable by free radical mechanisms and work has begun using chloroprene. It must be stressed, however, that the specificity and purity of the product Is largely controlled by the detailed kinetics of the radical polymerization process. In particular the prominence of chain transfer reactions and the nature of the termination step which will, of course, vary from monomer to monomer. 

Molecular Design and Polymerization Behavior of Monomers Polymerizable via Radical Ring-opening... 

Various monomers polymerizable via radical ring-opening other than those shown above have been also reported (Figure 18). 

Figure 18. Structures of various monomers polymerizable via radical ringopening.

Table 10.7 Chemical structures of monomers polymerizable by a cationic mechanism [2, 7].

Cetearyl methacrylate Isotridecyl methacrylate monomer, polymeric HALS 4-[3-(Diethoxymethylsilylpropoxy)-2,2,6,6-tetramethyl] piperidine monomer, polymerizable adhesives Lauryl methacrylate monomer, polymerizable caulks Lauryl methacrylate monomer, polymerizable floor waxes Lauryl methacrylate... 

Lauryl methacrylate monomer, polymerizable varnishes Lauryl methacrylate monomer, polymerization Dioctyl fumarate... 

Among the phosphorus-containing monomers, polymerizable DHPs are mainly used in current commercial enamel/dentin adhesives. One of the... 

Cyclohexyl methacrylate n. H2C=C(CH3) COOC6H11. A colorless monomer, polymerizable to resins for optical lenses and dental parts, and useful for potting electrical components (See image). 

FIGURE 21.8 Substituted acetylene monomers polymerizable with Rh-based catalysts. 

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