Polyepichlorohydrin crystalline

In the course of some of our work on polyethers, we encountered a series of crystalline polyepichlorohydrins which differed quite markedly in their processing characteristics but otherwise seemed quite similar. Differences revealed by the infrared and nuclear magnetic resonance techniques then available were too insignificant to be helpful in their characterization. All polymers were shown to be crystalline and isotactic by X-ray analysis. Small differences in optical activity were measurable. However, these differences were too small to be useful for correlation with physical properties. We found that an examination of their crystallization behavior and rates of crystallization was an extremely sensitive and revealing way of characterizing them. 

Spherulite Morphology. Crystalline polyepichlorohydrin readily forms spherulites on cooling from the melt. As shown in Figure 1, we have observed two kinds of spherulites. 

Microscopic and Dilatometric Melting Temperatures of Crystalline Polyepichlorohydrin... 

There are several interesting and unusual features about crystallization rates of polyepichlorohydrin illustrated in Figure 7. Evidently, there are not one or even two polyepi-chlorohydrins. Instead there is a whole family of crystalline polyepichlorohydrins. There are the "slowly crystallizing" members of the family like 8E. These polymers have a relatively sharp maximum and an intermediate melting temperature. 

The results of this study further reveal that the crystalline polyepichlorohydrin we have studied consists of isotactic sequences that can crystallize in the form of two different kinds of spherulites. We have shown that the two kinds of spherulites can cocrystallize- At present our educated guess is that all the polymers we have examined contain either Type I or a mixture of Type I and Type II spherulites in varying proportions. The polymers that crystallize most rapidly and that have the highest melting temperatures have some optical activity and their films contain predominantly Type II spherulites. We conclude that the Type II spherulites are obtained from optically active polymer sequences. We do not mean to imply that all sequences in these... 

The purposes of this study were to determine what chemical and physical structures are present in polyepichlorohydrin and to correlate these structures with the crystallization rates observed microscopically and dilatometrically. Crystallization rates were shown to be an extremely sensitive way of characterizing these polymers. For example, the study revealed that the crystalline polyepichlorohydrins examined consisted of isotactic sequences that can crystallize as two different kinds of spheru-lites, arbitrarily called Type I and Type II. The two types can cocrystallize. The polymers that crystallize most rapidly and that have the highest melting temperature have some optical activity. Their films contain predominantly Type II spherulites. Polymers that contain Type I spherulites melt lower and show little or no optical activity. These polymers are racemic mixtures. 

Figure 8 shows the carbon-13 NMR spectra of crystalline polyepichlorohydrin and the poly(propylene oxide) it yielded by dechlorination with LAH. The poly(propylene oxide) was also highly crystalline (m.p. 64 C. by DTA) and its carbon-13 NMR spectrum corresponds closely to that reported for the isotactic polymer. Thus, the single methylene peak at about 70.2 ppm. in the spectrum of crystalline polyepichlorohydrin is due to isotactic dyads. The poor resolution in this spectrum is due to low solubility of the crystalline polymer in the benzene solvent. No trace of the peaks due to polyepichlorohydrin are observable in the spectra of the poly(propylene oxide) obtained by dechlorination. In addition, the number of observable peaks does not increase as a result of the LAH treatment. This is further evidence that the dechlorination reaction results in smooth replacement of Cl with H without otherwise altering the structure of the polymer. 

Figure H. Carbon-13 NMR spectra of (A) crystalline polyepichlorohydrin and (B) the poly(pro-pylene oxide) obtained by dechlorination with LAH...

Epichlorohydrin Elastomers without AGE. ECH homopolymer, polyepichlorohydrin [24969-06-0] (1), and ECH—EO copolymer, poly(epichlorohydrin- (9-ethylene oxide) [24969-10-6] (2), are linear and amorphous. Because it is unsymmetrical, ECH monomer can polymerize in the head-to-head, tail-to-tail, or head-to-tail fashion. The commercial polymer is 97—99% head-to-tail, and has been shown to be stereorandom and atactic (15—17). Only low degrees of crystallinity are present in commercial ECH homopolymers the amorphous product is preferred. 

Inasmuch as the use of epichlorohydrin concept, Agel et al. [13] developed a new and cheap type of anion exchange membranes (AEM) by preparing the polyepichlorohydrin (PECH) graft quaternary amines (DABCO, TEA) for use in alkaline cells. It s a quasi-gas impervious polymer membrane. The ionic conductivity was much improved to 10 S cm due to the low crystallinity and the anion exchange between Cf and OH ions on the polymer side chains. For the first time, the alkaline SPE employed in alkaline fuel cell, the test results exhibited good performance and could tolerate at high temperature up to 120°C. 

In fact, there is a direct parallel to some of our findings reported in the case of crystalline polypropyleneoxide, which is structurally the same as polyepichlorohydrin except that the chlorine atom on the pendant methylene substituent is replaced by a hydrogen atom. Two kinds of spherulites have been observed in crystalline polypropyleneoxide (14). The two were not shown to cocrystallize. 

The assignment of the 70.17 ppm. peak to isotactic dyads in polyepichlorohydrin was confirmed by observing the spectrum of crystalline material prepared by a published procedure (10). 

With this complex, partially crystalline, soluble polyepichlorohydrin with viscosity-average molecular weights greater than 2 x 10 and yields greater than 70 percent were obtained. 

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