The molecular mobility of a polymer in the solid state can be determined by NMR relaxation measurements. The analysis of proton spin-lattice relaxation time (T1H) and proton spin-lattice relaxation time in the rotating frame (T(1)H(r)ho), allow information to be obtained about the behaviour of homogeneous samples. The response of this behaviour can be extracted by NMR solid state techniques such as: magic-angle spinning (MAS) variable contact time, inversion-recovery, spin-locking, delayed contact time and cross polarization-MAS.