Separation of 13 C spectra of polyurethane soft and hard segments by ROSY The ROSY (Relaxation Ordered SpectroscopY) is a method in which the 13 C CPMAS spectrum of a mixture is classified by a longitudinal relaxation time of 1 H, and the 13 C CPMAS spectrum is displayed separately for each substance. In solution NMR, each peak in the 1 H spectrum has its own longitudinal relaxation time. In solid-state NMR, however, spin diffusion occurs due to the dipolor interaction between 1 H, and all 1 H have the same longitudinal relaxation in the domain within a certain distance. The 13 C spectrum can be separated for each domain by using this difference in relaxation time of 1 H. The longitudinal relaxation time ( T 1 H ) obtained by the saturation recovery method as shown in Fig.1a is usually used to separate the 13 C spectrum of the mixture. The size of the domain that can be separated by this method is about 100 nm. To separate domains smaller than this, a measurement using the relaxation time at rotational flame ( T 1ρ H ) obtained by the spinlock method as shown in Fig.1b is effective. The domain size that can be separated by T 1ρ H is about several nm, and it is possible to determine the phase separation structure of block copolymers and the molecular compatibility.