Chain-Folding Structure of a Semicrystalline Polymer in Bulk Crystals Determined by C-C Double Quantum NMR.

A unique approach using C-C double quantum (DQ) NMR combined with selective C isotope labeling is proposed to investigate the chain trajectory of the synthetic polymer in bulk crystals. Since the DQ buildup curve highly depends upon coupled spin number, topology, and internuclear distance, which originated from the chain trajectory of selectively C-labeled polymers, the adjacent re-entry site and fraction under finite chain-folding number can be determined.