Crystallization polyepichlorohydrin

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. 

Figure 1. Polyepichlorohydrin spherulites. Left Type I spherulites from 329C after melting at 170°C and crystallizing at 50°C for 185 min. (128x). Right Type 11 spherulites from 39A after melting at 150°C and crystallizing at 30°C for 222 min. (128x).

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. 

Overall crystallization rate of blends of "fast" and "slow" crystallizing polymers. We obtained further evidence that the greater ease of nucleation of optically active polymer into Type II spherulites is responsible for the observed increase in crystallization rate by studying solution blends of 2413 and a nonopt-ically active polyepichlorohydrin. We found that addition of only 6% of 2413 reduced the ti at 50"C of the blow" polymer from 32 min to less than 10 min. 

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. 

Blends of polyepichlorohydrin and poly-epsilon-caprolactone have been investigated. The blends are miscible but, at levels above about 30 percent polylactone, phase separation that is caused by the strong crystallization tendency of the polylactone takes place (113). The relation... 

Isotactic polyepichlorohydrin crystallizes with an orthorhombic unit cell that has the dimensions a = 12.6A, b = 4.90A, and c = 7.03A and a zigzag conformation that differs from planar by 15 degrees (97, 98). There are four monomeric units in the unit cell. The chloromethyl side group lies on a plane essentially perpendicular to the main chain axis. Calculated density is 1.47 g/cm. ... 

Applied Crystallization Kinetics. III. Comparison of Polyepichlorohydrins of Different Stereoregularity... 

---