Units, free radical experiment

At least 90 percent of free-radical-polymerized 2,3-dimethylbutadiene consists of 1,4 units according to ozone degradation experiments. Successive substitution of the methyl groups on carbons 2 and 3 of butadiene is seen to increase the proportion of 1,4 units formed. In polychloroprene no less than 97 percent of the structure consists of 1,4 Cl... 

However, v is not a quantity which can be obtained directly from experiments. On the other hand, it is possible to determine analytically S, the ratio of initiator units [r] to monomer units [m] in the polymer. The initiator units are incorporated into the polymer only through the start reaction and by termination with the initiator free radicals ... 

Free-radical initiation of the polymerization of pcrfluorobut-2-yne is difficult, and the solid polymer has previously been obtainable only by y-ray initiation or by a fluoride-initiated anionic pathway. - " A new technique now disclosed involves the use of trifluoromethyl hypofluorite, which at sub-ambient temperatures catalyses the conversion of the butyne to a polymer which is quite stable at 450 "C. Mass spectrometric analyses of the oligomers obtained by the anionic pathway, containing up to twelve butyne units, are consistent with an all-fra s conjugated polyolefin structure H—[CfCFs) C(CFa)]B—F. This result is wholly consistent with trapping experiments in which the incipient vinyl anions are intercepted by, for example, penta-fluoropyridine to give /ranj-olefins and /ranj,fra j-dienes. - ... 

CRPP sample production was carried out in a Haake Rheocord 90 unit equipped with a Rheomix 3000 batch mixer. Experiments were carried out at various temperatures (230, 250, 270 and 290 C) and NOR free radical generator concentrations (0, 0.75%, 1.5% and 3%). Expoiments using the paoxide initiator were carried out only at one concentration of 250 ppm. At each set of conditions, samples wo-e collected at a preset run time of 5 minutes. All experiments were carried out at 100 rpm. 

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