Conformational Disorder and Its Dynamics Within the Crystalline Phase of the Form II Polymorph of Isotactic Poly(l-butene)

摘要

13C 2D exchange NMR under conditions of magic-angle-spinning has revealed that the metastable form II polymorph of isotactic poly(l-butene) exhibits significant slow conformational exchange (in the milliseconds to seconds time regime) above the amorphous-phase glass transition. Comparison with spectra of the form I polymorph proves that this motion occurs within the crystalline regions. The observed dynamic conformational disorder within the crystalline regions of this semicrystalline polymer is characteristic of what some call a macromolecular condis crystal. The presence of motion within the crystalline regions is consistent with previous calculations of the conformational flexibility of this polymer.