Tracer Studies of Oxidation—Reduction Polymerization and Molecular Weight of “Teflon” Tetrafluoroethylene Resin

Abstract

overnight. After washing with water and drying, the crude product was distilled, yielding 19.4 g. (33%) of X a t 240-242' and 0.05 mm., n% 1.4318.Anal. Calcd. for C~oH~~o0~~Sia: Si, 9.58; MRD, 325.3; mol. wt., 1172. Found: Si, 9.84, 10.01; MRD, 321.7; mol. wt., 1143. Heptakis-( 1,3-dimethylbutoxy)-trisiloxanol (XI) .-Eightyfive grams (0.143 mole) of the disiloxanol (IX) was added dropwise with stirring to a cold mixture of 42 g.(0.140 mole) of IT and 30 g. of dry pyridine. After an hour 70 ml. of water was added rapidly and stirring was continued for an additional hour. The organic layer was extracted with ether, washed with water, and dried over magnesium sulfate. After removal of ether the crude product was distilled, yielding 75 g. (65%) of XI at 185' and 0.1 mm., %' OD 1.4255. mol. wt., 841. Found: Si, 10.5, 10.9; MRD, 228.2; mol. wt., 840, 843. (XV).-Efforts to isolate the trialkoxysilanol derived from 2-ethylhexanol were unsuccessful and this silanol was prepared in situ by addition with stirring of 66.7 g. (0.148 mole) of the chlorosilane (XII), over a period of 2 hours, to 2.66 g. (0.148 mole) of water in 100 ml. of dry pyridine. During the next half-hour 24.6 g. (0.074 mole) of bis-( 2-ethylhexoxy)-dichlorosilane (XIII) was added, and stirring was continued for an additional half-hour. The reaction mixture was washed with water, dried and distilled. Thirty-five grams (41%) of XV was collected a t 260-269' and 0.05 mm., n% 1.4428. Octakis-(2-ethy1hexoxy)-trisiloxaneSince the polymer is insoluble and infusible, attempts were made to introduce and determine radiosulfur-containing end groups derived from persulfate initiator. Polymers initiated by persulfate activated thermally or by reaction with Fe++ or bisulfite did not contain sulfur from the persulfate. When bisuEte containing radiosulfur was employed in oxidation-reduction initiation reactions with persulfate or Fe+++, polymers with non-hydrolyzable sulfur-containing end groups from the bisulfite were obtained. These results are explained on the basis that the following are the most probable radical-producing reactions in decreasing order of effectiveness for initiating tetrafluoroethylene polymerization.The objective of this work was to determine the molecular weight of polytetrafluoroethylene.The translation of radioactive end group determinations to molecular weights is based upon the foregoing view of the initiator reactions and the assumptions (1) that there is no chain transfer or disproportionation in the polymerization, and (2) that termination is by combination of radicals. The number average molecular weights of some relatively low molecular weight polytetrafluoroethylenes are in the range 142,000-534,000.

Synthesis of 3,6-dioxa-Δ7-4-trifluoromethyl perfluorooctyl trifluoromethyl sulfonimide: bis[(perfluoroalkyl)sulfonyl] superacid monomer and polymer

“…The iron/bisulfite/persulfate initator system was used because at low temperatures the reaction rate of persulfate-bisulfite initiators with TFE emulsion copolymerizations is quite slow [47]. Berry reported that the reaction between persulfate and bisulfite was found to have a threshold initiation temperature for tetrafluoroethylene of 35-36 8C, while the bisulfite/iron initiator had a threshold initiation temperature for TFE of 0-10 8C [48]. The source of iron in our polymerizations was from the buffer salts as well as the 316 ss autoclave.…”

Transition Metal-Mediated and Metal-Catalyzed Carbon–Fluorine Bond Formation

“…Alkenyl fluorides have utility as monomers for free-radical polymerization to form fluorinated polymers (e.g., Teflon) [184,185], and as peptide mimics due to the similarity in size and dipole moment between amide bonds and fluoroalkene groups [186][187][188][189][190]. While fluoroalkene synthesis is often accomplished using Wittig-type reactions [191][192][193][194][195], several examples have been reported using gold catalysis and alkyne substrates.…”

Factors affecting the thermal stability of polytetrafluoroethylene

“…Polyethylene decomposes appreciably, 0.16 percent p CI' minute at 385 0 C; poly tetrafluoro ethylene decomposes at the same rate at 489 0 0, only 104 deg higher [9,25]. For comparison, bond-dissociation energies in related simple molecules are: for C2H 6 and other lower paraffin , C-C = 80 kcal, C-H = 101 kcal ; for C2F 6 , C-C = 124 kcal, C-F = 107 kcal. All figures except C-F arc derived from electron-impact data.…”

“…Berry and Peterson [6] polymerized tetrafluoroethylene in the presence of radioactive sulfur compounds to secure an estimate of the molecular weight of th e polymer. The molecular weight of poly tetrafluoroethylene has never been measured directly, because no solvent for this polymer is lmown.…”