Segmental Diffusion in Rubbers Studied by Neutron Quasielastic Incoherent Scattering

1974 ◽  
Vol 47 (5) ◽  
pp. 1127-1135
Author(s):  
Geoffrey Allen ◽  
J. S. Higgins ◽  
C. J. Wright
Keyword(s):  
Lattice Relaxation ◽  
Activation Energies ◽  
Spin Lattice Relaxation ◽  
Self Diffusion ◽  
Spin Lattice ◽  
Nuclear Spin Lattice Relaxation ◽  
Relaxation Measurements ◽  
Poly Ethylene Oxide ◽  
Poly Ethylene ◽  
Poly Propylene

Abstract Neutron scattering experiments on polymethylphenylsiloxane, poly(propylene oxide), poly(isobutylene), and poly(ethylene oxide) show broadening in the quasi-elastic region similar to that previously reported from polydimethylsiloxane. Measurements on partially deuterated samples confirm that the effect arises from segmental diffusive motion, rather than rotations of pendent side groups. The temperature dependence of this motion gives activation energies which are smaller than the activation energies for self-diffusion obtained from experiments of longer time-scale such as nuclear spin-lattice relaxation measurements and viscometry.

Study of Li Diffusion on Metal and Semiconductor Surfaces via NQI Presented at the XVth International Symposium on Nuclear Quadrupole Interactions

2000 ◽  
Vol 55 (1-2) ◽  
pp. 15-20
Author(s):  
H. J. Jänsch
Keyword(s):  
Crystal Surface ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Β Decay ◽  
Spin Lattice ◽  
Quadrupole Interactions ◽  
Nuclear Quadrupole Interactions ◽  
Nuclear Spin Lattice Relaxation ◽  
Relaxation Measurements ◽  
Nuclear Quadrupole

Nuclear magnetic resonance has been used to study the diffusion of lithium on a Ru(001) single crystal surface. The quadrupolar interaction of the radioactive probe nucleus 8Li was utilized for this. In an online experiment the 8Li nuclei are produced, thermalized and highly polarized before they land on the surface studied, the parity violating β-decay revealing the sought after NMR/NQI nuclear information through the spatial asymmetry of the decay electrons. As a function of substrate temperature, alkali metal coverage and magnetic field the nuclear spin-lattice relaxation measurements show the existence of two distinctly different diffusion barriers on the surface, valued at 0.45 eV and 0.15 eV. The former is attributed to jumps from step to terrace sites, whereas the latter is the barrier between adjacent terrace sites. On the substrate Si(l 11)7x7 the relaxation measurements suggest a much higher diffusion barrier around 0.8 eV.

A Study of Thermal Motion of Ammine Groups in Carbonatotetramminecobalt(III) Sulfate

1973 ◽  
Vol 51 (7) ◽  
pp. 1107-1108 ◽  
Author(s):  
B. A. Dunell ◽  
M. D. Pachal ◽  
S. E. Ulrich
Keyword(s):  
Hydrogen Bonding ◽  
Lattice Relaxation ◽  
Activation Energies ◽  
Thermal Motion ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Relaxation Measurements

The results of spin–lattice relaxation measurements are reported for carbonatotetramminecobalt(III) sulfate. The observed TI minima and activation energies, 1.9 and 4.3 kcal, for the reorientation of ammine groups are interpreted on the basis of hydrogen bonding effects.

Sign in / Sign up

Export Citation Format

Share Document