Qualitative and quantitative analysis of solid state free induction decay (H-1 NMR) curves using a combination of the methods of Gardner and Prony: Isotactic polypropylene as a case study

A combination of the methods of Gardner and Prony is used for the qualitati ve and quantitative analysis of solid-state free induction decay (H-1 NMR) curves of isotactic polypropylene, recorded at 40, 60, 80, and 100 degrees C at constant time intervals. These multicomponent decay curves contain inf ormation about the physicochemical structure of the polymer sample: each co mponent is characterized by a specific model function containing a spin-spi n relaxation time T-2 and an intensity as parameters depending on the prope rties and amount of the corresponding phase. The number of phases is still an unanswered question. Each FID curve is analyzed by using an improved met hod of Gardner ct al. in order to reveal the number of phases, to predict t he best fitted model function, and to estimate the T-2 value of each compon ent. The quantification of the parameters (T2 and fraction) with Prony's im proved method is discussed. The presence of an intermediate phase is unambi guously demonstrated. The influence of temperature on the physicochemical s tructure of the polymer is examined. The precision of the computed paramete rs is discussed for the analyses of three consecutively measured FID curves of isotactic polypropylene at 60 degrees C.