th  - 1988 - 51st ENC Conference

35 DYNAMIC NUCLEAR POLARIZATION STUDIES OF A MOLECULARLY
DOPED POLYMER by Robert A. Wind, Liyun Li, and Gary E. Maciel,
Department of Chemistry, Colorado State University, Fort Collins, CO 80523,
Nicholas Zumbulyadis," Corporate Research Labora~ri~, Eastman Kodak
Company, Rochester, NY 14650, and Ralph I-L Young, Copy Products Research and Development,
Eastman Kodak Company, Roches~r, NY 14650.
Small organic, charge-transporting molecules doped into inert polymer mal~ices offer many advantages
as model systems for the study of elect~nic processes in amorphous materia~ We have studied
samples of bisphenol-A-polycarbonate doped with various amounts of trianisylaml-lum percMorate
and U~misylamine using pm~m DNP and C-13 DNP/CPMAS and DNP/HDMAS experiment~ The
H DNP experiments indicam that the electron-proton interactious have both a time-independent and
a ~ d e n t component. The former lead to enhancements due to the solid-stats and thermal
mixing effects, the latter to an Overhauser enhancement. The Overhauser enhancement is positive,
indicating that scalar electron-proton interactions dominat~ The addition of free amine reduces the
proportion of Overhauser enhancement.
The C-13 DNP/FIDMAS experimenm indicate differcntiat proton nuclear Overhauser enhancement as
well as a mixture of solid-state, thermal mixing and Overhauser enhancement due to the unpaired
• ele~mnL The implications of these obeervations for charge mobility and small molecu/e clustering
in the polymeric matrix will be diwume&
36 I
FREQUENCY SWITCHED INVERSION PULSES AND THEIR APPLICATION TO
BROADBAND DECOUPLING; Toshimichi Fujiwara and Kuniaki Nagayama
Biometrology Lab, JEOL Ltd. Nakagami, Akishima, Tokyo 196, Japan
First, the broadband inversion pulses with coherent
frequency switching were designed. They are made of a few
180°-like pulses which are different in frequency of about
1.5 x B , where B indicates strength of r.f. field. The
refined frequency differences and pulse widths were numerically
searched under the constraint of symmetry about offset frequency.
The operative frequency range of these pulses is about
1.2 x B x n, where n is the number of frequencies used, or the
number of 180 ° pulses in the sequence. Second, its performance
and the tolerance to inhomogeneity of B field were improved by
the phase cycling of 0 °, 150 ° , 60 ° , 150 ° , 0°. * Finally,
decoupling pulse sequences were constructed from these improved
inversion pulses using the phase cycle employed in MLEV-°4. The
performance of these pulse sequences was experimentally tested,
and theoretically evaluated with two scaling factors; J-scaling
factor which characterizes the decoupling on a long time scale
(long period scaling) and a scaling factor which characterizes
the decoupling on a short time (short period scaling).
*R.Tycko, A. Pines, Chem. Phys. Letters ll__!l, 462 (1984).
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