Several types of poly(vinyl formal) (PVF), copolymers of six-member formal rings and unreacted vinyl alcohol, prepared by different methods of synthesis out of atactic poly(vinyl alcohol) (PVA) were studied by NMR thermal analysis, and wide-angle X-ray diffraction (WAXD). While thermal analysis and WAXD provide useful information about the macroscopic properties (e.g., T-g, crystallinity, T-m), solid-state NMR does focus more on the microscopic properties like molecular phase separation and molecular dynamics. The PVF polymers are composed of rigid and mobile molecular domains of which the distribution is mainly determined by the tacticity of the original atactic PVA polymer.