Abstract: The internal rotation of side chain in AB-crosslinked polymer(i.e.ABCP) based on the prepolymer of polypropyl oxide urethane (PPU) and polymethacrylates (PMAs) was studied by high resolution solid state NMR by means of ¹³C spin-lattice relaxation time, T₁. The ¹³C T₁ values were analyzed by using the average spectral density function for nth internal rotation. The results show that the longer the distance between the main chain and the side chain, the faster the rotation of the side group in PMAs and the rotation of the side-CH₃ group in PPU becomes faster as the glass temperature of PMA decreases. The phase behavior and the compatibility between the two components were also studied by using ¹H T_1ρ, ¹H T₂ and proton spin diffusion measurement. Information about the composition of each phase in corresponding scale and the domain size of the soft phase were obtained.

Key words: Relaxation, AB-crosslinked polymer, Spin-diffusion, Molecular motion, Compatibility, Phase behaviors