Polar vinyl comonomers

Correia SG, Marques MM, Ascenso JR, Ribeiro AFG, Gomes PT, Dias AR, Blais M, Rausch MD, Chien JCW (1999) Polymerization with TMA-protected polar vinyl comonomers. II. Catalyzed by nickel complexes containing a-diimine-type ligands. J Polym Sci A Polym Chem 37 2471... 

Acrylamide copolymerizes with many vinyl comonomers readily. The copolymerization parameters ia the Alfrey-Price scheme are Q = 0.23 and e = 0.54 (74). The effect of temperature on reactivity ratios is small (75). Solvents can produce apparent reactivity ratio differences ia copolymerizations of acrylamide with polar monomers (76). Copolymers obtained from acrylamide and weak acids such as acryUc acid have compositions that are sensitive to polymerization pH. Reactivity ratios for acrylamide and many comonomers can be found ia reference 77. Reactivity ratios of acrylamide with commercially important cationic monomers are given ia Table 3. 

A -Dimethylacrylamide and its miKtures Water with polar uncharged or ionic vinyl comonomers... 

Copolymers of vinyl viologens, such as N-vinylbenzyl-N -alkyl and benzyl and N-(x-mefliacroyloxy)propyl-N -propyl-4,4 -bipyridinium dihalides and polar aprotic comonomers, such as N- vinyl-2-pyrrolydone or N.N dimethylacrylamide exhibit a strong color formation upon irradiation. One such copolymer can be illustrated as follows ... 

When more than routine water resistance is required, a copolymer vinyl acetate emulsion can be used. The plasticizing comonomer in the polymer particles increases their intrinsic coalescing ability thus, they can coalesce more readily than homopolymer particles to a film that has a higher resistance to water. This resistance to water does not extend to the organic solvents, however, which are better resisted by homopolymer films. The soft copolymers have lower solubility parameters than homopolymers and are more readily attacked by solvents of low polarity, eg, hydrocarbons. 

Evidently, there are a number of factors that determine which of the above-mentioned pathways of polymerization occurs. One of these is the enrichment of final copolymers with the more hydrophilic comonomer (in comparison with the composition of the initial feeds), due to a higher reactivity of NVIAz. The higher (than for NVC1) reactivity of NVIAz is determined by a stronger polarization of the double bond of the vinyl group by the imidazole moiety as compared with the caprolactam cycle. Furthermore, a good solubility of hydrophilic NVIAz can also contribute to its higher reactivity in aqueous media. 

Theoretical attempts to correlate permeation with properties of the various monomers have not been entirely successful. However, molar volume and polarity appear to be important properties, the smaller and more polar comonomers giving rise to less Oj-permeation. No data are available for vinyl bromide however, on the grounds of molar volume and polarity, it may be assumed that O -permeation in VBr is similar to that in VCl. 

Ethylene may be copolymerized with a range of other vinylic compounds, such as 1-butene, 1-octene and vinyl acetate (VA). These are termed comonomers and are incorporated into the growing polymer. Comonomers that contain oxygenated groupings such as vinyl acetate are often referred to as "polar comonomers." Comonomer contents range from 0 to 1 wt% for HOPE up to 40 wt% for some grades of ethylene-vinyl acetate copolymer. 

The range of suitable comonomers depends upon the nature of the catalyst or initiator. For example, Ziegler-Natta catalysts are poisoned by polar comonomers. Hence, commercial copolymers of ethylene and vinyl acetate are currently produced only with free radical initiators. However, some single site catalysts are tolerant of polar comonomers (see section 6.2.1). 

Chain propagation during copolymerization of ethylene with polar comonomers can proceed in several ways depending on the nature of the macroradical end group and the monomer being added, illustrated with vinyl acetate in eq 2.1-2.4 ... 

Palladium/phosphine-sulfonate neutral complexes, reported by Drent, Pugh, and coworkers, could incorporate several polar comonomers such as methyl acrylate, vinyl ethers, methyl vinyl ketones, and silyl vinyl ethers. Other common comonomers such as vinyl acetate, acrylonitrile, and vinyl chloride showed very low comonomer incorporation, between 1% and 2% [48]. 

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