Vinylidene fluoride radical addition

The rate of combination of trifluoromethyl radicals to form hexafluoro-ethane has been measured by the flash photolysis of trifluoromethyl iodide coupled with rapid-scan i.r. spectroscopy in the absence of an inert diluent (At, N2, or COt) carbon tetrafluoride and tetrafluoroethylene were also formed, presumably via fluorine atom abstraction from trifluoroiodomethane by hot trifluoromethyl radicals (c/. ref. 27). Photolysis of trifluoroiodomethane has been used in studies on (i) the direction of radical attack on 1,3,3,3-tetrafluoropropene [- CFj CHI CHFCF, (75%) + (CFa)jCH CHFl (25%)] (ii) the rates of hydrogen abstraction from ammonia, ammonia-ethylene oxide, silane, trimethylsilane, tetramethylsilane, and cycloalkanes and (iiQ the competitive addition of the CFj- radical to ethylene and vinylidene fluoride. Radicals formed by photolysis of the fluoroalkyl iodides CFJ, C FJ, n-C,F,I, (CF,)jCFI, (CFaljCHI, (CFalaCDI, (CFa)jCClI, and (CFa)iCPhI (the last was synthesized by treatment of CFs CPh CTj with CsF and iodine in DMF) have been... 

According to this literature survey, most investigations have been performed photochemically and in most cases, the monoadduct is composed of two isomers, the ratio of which depends upon the electrophilicity of the telogen radical. In the case of fluoroalkyl iodides, such an olefin exhibits the same reactivity towards these telogens, whatever their structure. In addition, trifluoroethylene seems less reactive than vinylidene fluoride but more reactive than hexafluoro-propene. 

Table 11 shows very little variation in the orientation of the addition of trihalogenomethyl radicals to vinyl fluoride, but for vinylidene fluoride there is a 4.5-fold increase in the orientation ratio (kjkj across the table. This change in orientation does not follow polarity and suggests that steric effects may be having some effect. The rates relative to ethylene for the three fluorine-containing radicals are very similar. 

Table 12 there is a marked increase in the orientation ratio as the attacking radical becomes more bulky. With vinylidene fluoride the orientation ratio for perfluoro-t-butyl radicals is too large to measure. Even with perfluoro-isopropyl the orientation ratio (kjk is 103. In the other tables the orientation ratios for addition to vinyl fluoride and trifluoroethylene vary only slightly, but in Table 12 there is a marked increase as the radical becomes more branched. Perhaps the most striking feature of the table is that the increase in orientation ratio is almost entirely due to a reduction in the rate of addition to the most substituted end of the olefin. The relative rates of attack at the unsubstituted ends of vinyl fluoride and vinylidene fluoride vary only slightly across the table. In other words, the high orientation ratio is almost entirely due to the difficulty of addition at the substituted end of the olefin, a conclusion supported by the great variation in the relative rate of addition to tetrafluoroethylene (i.e. where both ends are fully substituted). 

The majority of vinyl polymers are regioregular with a head-to-tail sequence of monomer units (0, i.e. they are isoregic (2). Some of the most notable exceptions are the polymers obtained by free-radical addition reactions of the fluoroethylenes vinyl fluoride (VF), vinylidene fluoride (VF2), and trifluoroethylene (F3E), which incorporate significant amounts of head-to-head and tail-to-tail structural defects caused by reverse monomer addition (3). 

In order to achieve a good dispersion and coating of the nanotube surface with the polymer, Mandal and Nandi have designed a new compatibilizer (P2) containing a thiophene moiety and a poly(dimethylamino ethyl methacrylate) group. This compatibilizer was prepared by atom transfer radical polymerisation (Figure 4.2). The dispersion of compatibilizer-coated MWNT in iV,A -dimethylformamide was stable for more than for 3 months. The addition of the P2-coated MWNTs to the poly(vinylidene fluoride)... 

Tetramethyldiphosphine adds photochemically to vinyl and vinylidene fluoride to give the bisphosphines Me2P-CH2-CXF-PMe2 (X H or F), and tetrakis(trifluoromethyl)diphosphine similarly adds thermally (at 50 Q or photochemically to the same olefins and to tetrafluoroethylene. Free-radical additions of trifluorothioacetic acid to the olefins CHF CF2, CHarCFa, and CH2 CHF (see p. 138) have been described only one-way addition was observed. Bis(trifluoromethyl) disulphide adds to fluoro-olefins with u.v. Irradiation in Pyrex or silica apparatus in the vapour phase to yield a variety of 1 1 and telomeric adducts. The products are consistent with the following mechanism ... 

Maleic anhydride grafting (cont.) poly(styrene-co-divinylbenzene), 694 poly(styrene-co-isobutylene), 675, 689 poly(styrene-co-nfialeic anhydride), 676, 679 poly(vinyl acetate), 676, 694 poly(vinyl acetate-co-vinyl fluoride), 678 poly(vinyl alkyl ethers), 675, 679, 692, 701 poly(vinyl chloride), 683, 692, 693, 695, 702 poly(vinylidene chloride), 691 poly(vinyl toluene-co-butadiene), 689 radical—initiated, 459-462, 464-466, 471, 475, 476 radiation—initiated, 459, 461, 466, 471, 474 redox-initiated, 476 rubber, 678, 686, 687, 691, 694 to saturated polymers, 459-466, 475, 476 solvents used 460-463, 465, 466, 469, 474-476 styrene block copolymers, 679 tall oil pitch, 678, 697 terpene polymers, 679, 700 thermally-initiated, 462, 464-467, 469, 476 to unsaturated polymers, 459, 466-474 vapor-phase techniques, 464, 474, 475 to wool fibers, 476 Maleic anhydride monomer acceptor for complex formation, 207-210 acetal copolymerization, 316 acetone CTC thermodynamic constants, 211 acetone photo-adduct pyrolysis, 195, 196 acetylacetone reaction, 235 acetylenic photochemical reactions, 193-196 acrylamide eutectic mixtures, 285 acylation of aromatic acids, 97 acylation of aromatics, 91, 92 acylation of fused aromatics, 92, 95, 97, 98 acylation of olefins, 99 acylation of phenols, 94-96 acylic diene Diels-Alder reactions, 104-111, 139 addition polymer condensations, 503-505 adduct with 2-cyclohexylimino-cyclopentanedi-thiocarboxylic acid, 51 adducts for epoxy resins curing, 507-510 adduct with 2-iminocyclopentanedithiocarboxylic acid, 51... 

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