Relation between crystallinity degree and stability in solid state of high molecular weight poly(ethylene oxide)s

Crystallinity degrees exert influence on the stability of high molecular weight poly(ethylene oxide)s, POE's, in solid state. It was found that the degradation of these POE's is connected with an increase of crystallinity degrees. Samples being prepared under the terms of the strontium carbonate initiated bulk polymerization, without stabilizer, degradated during 18 days just after the polymerization has been brought to an end, while at the same time the crystallinity degrees rose by 7‐20% up to an end value of about 70%. On the contrary the phenothiazine stabilized sample preserved its starting crystallinity degree during the whole time of investigation without suffering a significant degradation. The POE prepared by the calcium amide initiated solution‐precipitation polymerization at room temperature exhibited a higher starting crystallinity degree of about 70% and, as a consequence, it was stable during the whole time of investigation. Because the bulk polymerization must be carried out at least at 90°C, the POE formed crystallizes from the melt and a greater part of amorphous zones results than in the case of the solution‐precipitation polymerization, rendering the polymer less stable. The parameters established for the unit cell in the monoclinic system remained unchanged during the whole time of investigation in spite of changes in crystallinity degrees and molecular weights.