Ethylene with hexafluoroacetone

Copolymerization of Ethylene with Hexafluoroacetone. Conversion curves at — 78° C for three different initial monomer compositions are... 

Radiation induced copolymerization of hexafluoroacetone xcith a-olefins has been done over a broad temperature range. From these experiments, it was confirmed that ethylene can be copolymerized below its critical temperature to give an alternating copolymer. A radical mechanism is involved at relatively high temperatures below —10°C, the mechanism has been confirmed to be ionic and may be cationic. Propylene can be copolymerized in a way similar to that of ethylene however, the rate of copolymerization was much slower. Isobutylene did not copolymerize with hexafluoroacetone at 0°C. A 1 2 adduct compound was obtained as the main product. At low temperatures, copolymerization proceeds to some extent. 

Copolymerization of Propylene with Hexafluoroacetone. The conversion curves of the copolymerization are shown in Figure 12 as a function of irradiation time for equimolar monomer mixtures at 0°, —35°, and — 78°C. The copolymerization rate is much slower than that of the copolymerization of ethylene and hexafluoroacetone. We have data at... 

Other interesting perfluoro ether stmctures can be obtained by copolymerization of hexafluoroacetone with ethylene oxide, propylene oxide, and trimethylene oxide with subsequent fluorination to yield the following stmctures (67) ... 

The copolymerization of carbonyl monomes with alkenes has been even less studied than that between different carbonhyl monomers. The radiation-initiated copolymerization of styrene with formaldehyde proceeds by a cationic mechanism with a trend toward ideal behavior, r = 52 and r2 = 0 at —78°C [Castille and Stannett, 1966]. Hexafluoroacetone undergoes radiation-initiated copolymerization with ethylene, propene, and other a-olefins [Watanabe et al., 1979]. Anionic copolymerizations of aldehydes with isocyanates have also been reported [Odian and Hiraoka, 1972]. 

Very recently, however, it has been shown by Lemal and Raghavanpillai that in case of the photochemical reaction of hexafluoroacetone (UFA) or trifluoroacetalde-hyde with various polyfluorinated ethylenes and propylenes, both regioisomers (types A and B) are formed with the combined yields ranging from 50% to 95% (Scheme 2.3). ... 

Low-temperature, liquid-phase, radiation-induced ( Co y-rays) copolymerization of hexafluoroacetone with ethylene yields the alternating copolymer [(CFs)2C 0 CH2 CH2]re propene appears to behave like its lower homologue in this respect, but the reaction proceeds much more slowly isobutene yields a... 

ETFE polymers ("TEFZEL") modified with termonomers require great care in synthesis to Insure optimum properties. Incorporation of ethylene near 50 mole % and control of degree of alternation near 90% must be maintained in order to prevent too high a concentration of hydrocarbon branches which result from radical rearrangement of ethylene diads and triads. This same type of rearrangement is the reason why such an unusual comonomer as hexafluoroacetone is effective in improving stress crack resistance. While the hydrocarbon branches also have a beneficial effect, they must be surpressed because they are sites for oxidative attack at processing conditions. 

Monomer (I) is synthesized from hexafluoroacetone and ethylene oxide in four steps as shown in Scheme 16.2 [8], Monomer (I) is a colorless liquid with a boiling point of 33°C and has a high polymerization reactivity. Monomer (H) is synthesized by the following continuous-flow, gas-phase process (Scheme 16.3). It is also a colorless liquid with a boiling point of 30-32°C. 

Hexafluoroacetone has been used as a photochemical source of trifluoro-methyl radicals in kinetic studies dealing with attack of the latter on ethylene," di-isopropyl ketone, methylchlorosilanes, the methylsilanes MejSi, MejSiF, MeaSiFj, and MeSiFj, methyl acetate and deuteriated methyl acetates, dimethyl and di-isopropyl ether, tetramethyltin (less precise data were obtained with McsB, Me Si, and Me Ge), methyl formate, and hydrogen sulphide, deuterium sulphide, hydrogen chloride, and deuterium chloride. The photolysis of hexafluoroacetone alone has received further detailed attention and trifluoromethyl radicals thus generated have been shown not to attack sulphur hexafluoride even at temperatures up to 36S °C. ... 

To prepare Teflon AF series, reactions of hexafluoroacetone (HFA) and ethylene oxide (EO) give rise to defluorinated 2,2-bis(trifluoromethyl)-4,5-difluoro-l,3-dioxole (BDD) monomer, followed by the copolymerization with tetrafluoroethylene (TFE). The physical properties of these amorphous copolymers are dependent upon the compositions in the copolymers as shown in Table 4.8. Currently, there are two commercial grades of Teflon AF polymers produced by DuPont, AF-2400 and AF-1600, which contain the composition of copolymers for which n = 0.87 and 0.65, respectively, where n is the molar ratio of the BDD monomers. 

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