Polyepichlorohydrin dechlorination

Dechlorination of Polyepichlorohydrin. Polyepichlorohydrin (5.0 g., 54 mmoles Cl) was transferred to a dry 28-oz. beverage bottle in a nitrogen-filled glove bag. The polymer was dissolved... 

Further confirmation of the uniformly head-to-tail structure of HERCLOR H elastomer was obtained from its carbon-13 NMR spectrum. Since no literature spectra of polyepichlorohydrin were available for comparison, the carbon-13 NMR spectra of the poly-(propylene oxideD resulting from dechlorination with LAH were also examined. Published spectra of poly(propylene oxideD with detailed peak assignments are available. 

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...

A procedure has been described for the determination of irregular head-to-head and tail-to-tail linkages in polyepichlorohydrin. This procedure involves dechlorination of the polymer with lithium aluminum hydride, cleavage of the resultant poly-(propylene oxide) with n-butyllithium, and analysis by gas chromatography to determine the relative amounts of the respective dipropylene glycols. 

---