Nuclear Magnetic Relaxation in Polytetrafluoroethylene and Polyethylene

Abstract

Nuclear magnetic resonance studies of the linear chain polymer polytetrafluoroethylene (Teflon) indicate the coexistence of two phases, each characterized by its own pair of relaxation times T₁ and T₂. Decomposition of the complex resonance lines and complex saturation curves into normal curves permits determination of the fraction of nuclei in each phase. It is suggested that the phases are the crystalline and amorphous regions of these polymers, and some additional evidence to support this suggestion is presented. The phase thought to be crystalline shows a marked line‐narrowing at the first‐order thermodynamic‐transition point near 293°K. The less complete data presented for polyethylene suggest the analogous presence of two phases, and the line‐shape analysis yields reasonable values for the degree of crystallinity.