Page 172 - Photoreactive Organic Thin Films

5. CHIRAL POLYMERS WITH PHOTOAFFECTED PHASE BEHAVIOR FOR OPTICAL DATA STORAGE 51

TABLE 5.1 Chiral Homopolymers with Side Chains Based on Asymmetric
Esters of Terephthalic Acid and Hydroquinone

Polymer" Main chain Side-chain structure n Phase transitions 1

P5*A Acrylate /~\ /~\ Sm F* 77 Sm C* 97 Iso
Q ff \\ Q O"- H
P5*M Methacrylate — <cvy,r-^ \=/ y\ >-^ gl 40 Sm C* 74 Sm A 85 Iso
O O \-~' 0
P4*A Acrylate 2 Sm B 50 Sm C* 88 Iso
P4*M Methacrylate 2 gl 40 Sm C* 78 Iso
P6*M Methacrylate 4 gl 30 IsoSm* 53 Iso
P6*ST Siloxane ,—, , 4 Sm B 33 Sm C* 51 Iso$
=
P7*M Methacrylate ,„.. , /° ' v— / " °v /" \ f V H 5 gl 30 IsoSm* 57 Iso
t*^ H ?'10 Vv // Vl y/ V^ W fi n 2n
P7*ST Siloxane ° ° ° 5 gl 18 IsoSm* 54 Iso
P8*A Acrylate 6 Sm B 55 Sm A 61 Iso
P8*M Methacrylate 6 gl 30 IsoSm* 64 Iso
P8*ST Siloxane 6 gl 25 IsoSm* 61 Iso
P8*S Siloxane ff~\ / 6 gl 24 IsoSm* 47 Iso (metastable)
(CHj),; — O— (' N ) — O /=\ ° — (
or gl 24 Sm C* 43 Sm A 47 Iso
O \-_y -Q
(equilibrium)
PL4*A Acrylate 4 gl 10 Iso
PL4*M Methacrylate \ff~\-Jj > _ \_J > 4 gl 15 Iso
/ \ / \ /^"A / \
Siloxane
PL4*S r -i — (CH.J,,— o ^^ o— <i y-o o-c^,., 4 gl 10 Iso
PL6*S Siloxane 6 gl 15 Iso
"The number in the polymer abbreviations corresponds to the total number of carbon atoms in
the chiral terminal group, P stands for polymer, and the last letter relates to the type of polymer
main chain. *In heating, *For the sample annealed 24 h at 20°C.

Smectic Blocks Grain Boundaries
\

FIG. 5.4 Sketch of the TGB A* structure.

grain boundaries. Within the model, which we suggest for the particular case
of the isotropic smectic phase, the small Sm A grains are -10 nm in diameter,
64
and the helical domains are about 250 to 300 nm long. Thus, all the
structural elements are smaller in dimension than the visible light wavelength,
and the mesophase appears visually as optically isotropic, in contrast to
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known TGB A* phases. In the near-UV range, the selective reflection from
the TGB lattice cannot be observed, because of the strong absorption of
phenyl benzoate groups. The phase still keeps the smectic ordering at the
molecular dimensions.