Molecular mobility of lyophilized poly(vinylpyrrolidone) and methylcellulose as determined by the laboratory and rotating frame spin-lattice relaxation times of 1H and 13C

Abstract

Laboratory- and rotating- frame spin-lattice relaxation times (T 1 and T1ρ) of 1H and 13C in lyophilized poly(vinylpyrrolidone) (PVP) and methylcellulose (MC) are determined to examine feasibility of using T1 and T1ρ as a measure of molecular motions on large time scales related to the storage stability of lyophilized formulations. The T1ρ of proton and carbon was found to reflect the mobility of PVP and MC backbones, indicating that it is useful as a measure of large-time-scale molecular motions. In contrast to the T1ρ, the T1 of proton measured in the same temperature range reflected the mobility of PVP and MC side chains. The T1 of proton may be useful as a measure of local molecular motions on a smaller-time-scale, although the measurement is interfered by moisture under some conditions. The temperature dependence of T1 and T 1ρ indicated that methylene in the MC molecule had much higher mobility than that in the dextran molecule, also indicated that methylene in the PVP side chain had a higher mobility than that in the MC side chain. © 2003 Pharmaceutical Society of Japan.