General Analytical Description of Spin-Diffusion for a Three-Domain Morphology. Application to Melt-Spun Nylon 6 Fibers

Abstract

The NMR spin-diffusion process taking place in a morphology represented by three different domains with arbitrary sizes and diffusivities is investigated. General analytical solutions valid for the full range of spin-diffusion times were obtained for a one-dimensional lamellar morphology. The accuracy of these solutions has been tested by predicting the domain sizes for a poly(styrene-b-methyphenylsiloxane) diblock copolymer and semicrystalline poly(ethylene oxide) and comparing them with previously reported data. The effects of large changes in the size of the interface domain and the spin-diffusion coefficients of this domain on the spin-diffusion decay and build-up curves can be analyzed by numerical simulations. General analytical solutions of the spin-diffusion equations were used for investigating the complex morphology of high-speed melt-spun nylon 6 fibers. The NMR mobile amorphous, NMR less-mobile amorphous, and crystalline phases of nylon 6 fibers hydrated with D2O were detected and quantified u...