Atactic PMEPL

Spectra obtained for atactic PMEPL and the stereocomplex formed by equal molar mixtures of the two isotactic polymers of opposite absolute configuration are presented in Fig. 3. In contrast to the isotactic case, no dependence on thermal history is found. These spectra are unexpectedly similar, and resemble the solution cast isotactic spectrum of Fig. 1. NMR spectra were also recorded for polymers of intermediate tacticity. PMEPL of optical purity 75% shows the same dependence on sample preparation as is found for the isotactic polymer whereas samples of optical purity 25% behave as the atactic case. Similar observations were made by Grenier and Prud homme by the comparison of other properties, including x-ray patterns, solubility and morphology. 

Figure 3. Solid state NMR spectra of (a) the stereocomplex and (b) atactic PMEPL.

---