2-DIMENSIONAL NMR DETERMINATION OF THE REGIOSEQUENCE DISTRIBUTION IN POLYEPICHLOROHYDRIN

The microstructure of an amorphous polyepichlorohydrin was investigate d using a variety of one- and two-dimensional NMR techniques. Assignme nts of both the proton and carbon chemical shifts for the four possibl e regiosequence triads were made. Homo- and heteronuclear coupling con stants were determined. From this knowledge, a method of using two-dim ensional NMR spectra of PECH to analyze its regiosequence distribution was developed. The method consists of taking a heteronuclear chemical shift correlation spectrum, integrating the peaks corresponding to th e regiosequence triads, and calculating the dyad concentrations using first-order Markovian statistics, which were shown to fit the data. Th e amorphous polyepichlorohydrin studies was found to be approximately 63 % head-to-tail and approximately 37 % head-to-head, tail-to-tail wi th short blocks of four to five head-to-tail monomer units before a re versal occurs. The results obtained were in good agreement with the ot her limited data published to date.