Segmental dynamics of head-to-head polypropylene and polyisobutylene in their blend and pure components

Segmental dynamics are measured in pure polyisobutylene (PIB), pure deuterium-labeled head-to-head poly(propylene) (hhPP), and a blend containing 70% PIB/30% hhPP by mass using 13C spin−lattice relaxation, 2H spin−lattice relaxation, and dielectric spectroscopy (DS). The NMR measurements are made between 313 K and 413 K (spin−lattice relaxation measurements are sensitive to motions in the nanosecond range), while the DS measurements (which span the second to microsecond range) are made between 225 K and 325 K. While NMR and DS monitor local dynamics over a wide range of temperature and time, NMR has the additional advantage of being able to determine the local motion of each component in the blend through isotopic labeling. The spin−lattice relaxation data are interpreted using a modified Kohlrausch−Williams−Watts (KWW) correlation function with a Vogel−Fulcher−Tammann−Hesse (VFTH) temperature dependence of relaxation time, giving temperature-dependent segmental correlation times from NMR in the short tim...