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Figure 7.13 X-ray diffraction pattern obtained on micro slides of the duramer obtained by
polymerization of the metallohelicate 20.
diffraction peak at 43 A
in the small angle domain, whereas two broad, diffuse bands were
observed at 4.6 and 11.3 A
, corresponding respectively to the molten alkyl chains and the
periodicity of the pillaring of the helicate subunits inside the column. Notice that for the
monomer
20
the peaks were found at similar values (42, 4.5 and 10 A
), confirming that
the columnar order is maintained during the polymerization procedure. Furthermore, the
narrowing of the diffraction peak in the small angle regime by increasing the temperature
is in keeping with a better organization of the column inside the polymeric network (Fig-
ure 7.13).
It appear that the polymerization kinetics depend on the ordering effect of the polymer-
izable groups, anisotropic mobility, and diffusion in the liquid-crystalline medium. Heli-
cates
18
and
19
were less well suited to the formation of reproducible material (
duramer
)
than
20
, which seems the best starting material to generate homogeneous polymeric net-
works. A schematic representation of the overall process is shown in Figure 7.14.
Figure 7.14 Schematic representation of the columnar arrangement of metallohelicate 20
before polymerization as deduced from X-ray power diffraction (left part) and after polymeri-
zation (right part) as deduced from X-ray diffraction on microslides of the polymer.
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