Divinylbenzene (48%)/ethylvinylbenzene copolymer was converted to a series of pyrolytic derivatives. Enough of the carbon bond network remained intact throughout thermal rearrangement and condensation to retain the original gross shape of the copolymer in the final polymer carbon. Although a carbon residue (6% by weight) was obtained by direct heating of the copolymer, yields were increased eightfold by preoxidation or prechlorination. Such an alteration of thermal degradation is obviously a complex process involving both “inhibition,” in the ordinary sense, and a considerable contribution toward an increased valence network density. As a consequence, the average molecular weight of volatile fragments evolved during carbonization is inversely proportional to the oxygen content of the original hydrocarbon polymer. Pyrolysis of divinylbenzene copolymer, containing 18% oxygen, resulted in a 50% volume shrinkage, 50% weight loss, and a 100% density gain. Unless these data are attributable to extensive microporosity, it is difficult to account for the sorption of up to 3 cc. of helium gas per gram of polymer carbon at 30°C. and 600 mm. pressure; and calculated surface areas as large as 1400 sq.m./g. Abrupt changes in the progress of polymer carbon formation occurred between 600 and 700°C. The residue became rigid; vigorous evolution of volatile products, principally hydrogen, suddenly diminished; and paramagnetic resonance absorption (unpaired electron concentration) dropped about tenfold while d.c. resistivity decreased 106 ohm cm. In this region, also, x‐ray patterns were most diffuse, exhibiting no maxima characteristic of carbon scattering in either hydrocarbons or condensed rings. Finally, the x‐ray patterns of polymer carbon intermediates became less diffuse in samples prepared at 700°C. or above. Yet, scattering indicated the presence of crosslinked graphitic layers of such stability that reordering or true graphitization did not occur at 2400°C.
In the case of dodecylamine hydrochloride the conductivity rises in the third range in spite of greatly increased viscosity.5. The values of A0 and lc have been determined from the experimental data. Chicago, Illinois
Because of the known chemical structure and comparatively high degree of crystallinity of linear polyesters and polyamides these substances offer excellent subjects for the study of the physical behavior of polymeric systems. Previous investi-gations1s2 have shown that the crystallinity exhibited by these long-chain compounds has much in common with that of the simpler and more fully studied low molecular chain molecules. Thus, it has been shown that fully extended (zigzag) primary valence chains packed in parallel fashion are nearly always present. Further, analogous to the shorter homogeneous chain crystals, different modes of packing giving rise to different lattice-like arrangements often apparently exist in the same polymeric compound.There are several respects, however, in which these synthetic linear polymers differ from the low molecular compounds. Most outstanding are the striking changes in physical properties which occur with sufficient increase in average chain length and the high degree of polycrystallinity exhibited by these substances. The changes in physical characteristics are chiefly pronounced increase in strength and flexibility. Experiments have shown that the latter is probably related to amorphous portions present in these systems.' Furthermore] recent conceptions of the nature of natural high polymers have strengthened the view that both crystalline and amorphous matter exist in these substances.6'6 It is of great importance, therefore] to investigate polymeric compounds of known constitution in order to learn more about the origin of the crystalline and amorphous components and the factors controlling their formation. It is for this reason that the present work was undertaken. The experiments reported relate to changes in the crystalline nature and in the elastic properties of linear polyamides as a result of quenching and annealing. Although the interpretation of the observed effects is in no way complete, the results (1) Fuller and Froseh, J .imply a considerable rotational freedom of the chain molecules in the solid state and are in agreement with the conception of statistical units or segments of the long-chain molecules present in the solid in different states of organization. Part I. X-Ray ExaminationExperimental.-Two polyamide compounds were investigated, polyhexamethylene adipamide of intrinsic viscosity in cresol a t 25' of 0.974 and polyhexamethylene sebacamide of intrinsic viscosity 1.021. The crystalline behavior of these compounds was studied under two types of heat treatments. One treatment consisted in quenching the materials from a fixed temperature above the melting point. The other consisted in an annealing of previously quenched samples. The latter treatment was applied to the polyamides both in the unoriented and in the oriented states.In the quenching treatments the polyamides were first melted in a hydrogen atmosphere to prevent oxidation and then brought to temperatures of 260 and 280' for the hexamethylene sebacamide and adipamide, respectively. An automatically co...
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