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HO
OH
OH
phytantriol
L
α
L
2
FLUID
Lower
η
Q
la3d
τ
oPs
= 3189 ps
τ
H
II
oPs
= 3133 ps
d = 7.52 Å
τ
d = 7.46 Å
Q
Pn3m
oPs
= 3117 ps
Higher
η
τ
d = 7.43 Å
oPs
= 3026 ps
RIGID
τ
d = 7.31 Å
oPs
= 2884 ps
d = 7.12 Å
Figure 4.8
Orthopositronimum lifetimes and rheological properties of different
mesophases of phytantriol (Dong et al., 2009).
4.2.6
Electron Microscopy
Electron microscopy (EM) techniques offer the potential for direct visualiza-
tion of LLCs at
5-nm resolution in both bulk and dispersed form (see later).
Transmission (TEM) and scanning (SEM) techniques have been used to
explore different aspects of LLC behavior. TEM, with its high resolution and
ability to image the internal structure of materials, has been extensively
employed to study LLC phase nanostructure.
The general approach to TEM analysis is to prepare a sample as a thin fi lm
such that an electron beam can pass through it. The image is collected with
contrast resulting from differential absorption and scattering from different
regions of the sample. These differences may be natural, or enhanced via the
use of heavy-metal stains (e.g., osmium tetroxide), to generate either negative
or positive contrast. Many EM-based techniques originally developed for
the study of biological specimens have been applied to LLC systems. As
with biological specimens, however, the risk of image artifacts due to sample
preparation and the requirement for vacuum during imaging requires careful
consideration (Bangham and Horne, 1964; Delacroix et al., 1996; Moren et al.,
2000 ).
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