Synthesis and characterization of novel jacketed polymers and investigation of their self assembly and application 6

Chapter 6

Conclusions













157
Considerable research interests are focused on synthetic polymer design strategies that
provide greater control over polymer size and shape than hitherto possible in commercial
polymers. Molecular stiffness enables the precise placement and functional control of
shape-persistent polymers. Stiff polymers, combined with precise molecular placement,
are good candidates for the construction of fine microstructure. Compared with normal
rigid building blocks, the jacketed polymers have great advantages for the synthesis. In

our approach, the conjugated rigid group was chosen as side groups. Besides the steric
crowding, the rigid properties of the side chains help polymers to take some ordered
conformation. Terphenyl or pentaphenyl group using as a laterally attached mesogenic
core incorporated on the side chain is rarely reported. The sufficient electronic interaction
between theses groups is expected to help the self-assembly of the polymers. The length
of the alkyl chain and position of the alkyl chain on the mesogenic units appears to have
significant effect on the self-assembly. Besides microseparation between rigid segments
and flexible segments, polar or nonpolar effect is investigated through the incorporation
of the polar functional groups.
A series of novel jacketed polymers were synthesized according to this strategy. Strong
electrostatic, weak van der Waals interactions, and geometrial effects were incorporated
on the mesogens attached to the polymer backbone to control the self-assembly of
polymer chains in the lattice. DSC and POM results show that the polymers with
pyrimidine groups on the aromatic rigid core exhibits mesophase with an isotropic
transition at 105 °C. X-ray diffraction experiments indicate a rectangular column-type
mesophase with the lattice constants a = 35.87 Å and c = 58.92 Å. Studies on structure-
property relationship of the polymers incorporated with alkyl chains and pyrimidine

158
groups revealed that the alkyl chains in the lateral position on the rigid core exert
hindrance to self-assembly whereas the pyrimidine groups stabilized the self-assembly of
jacketed polymers.
A series of novel jacketed liquid crystalline polymers, in which the terphenyl aromatic
rigid core with alkyl chains on the terminal position attached laterally to the polymer
backbone with a short spacer, were synthesized and characterized. All polymers were
characterized using GPC, TGA, DSC, POM and XRD. The DSC, POM and XRD results
show that poly (4, 4”-dibutoxy-5’-methoxy [1, 1’, 4’, 1”] terphenyl-2’-yl acrylate) (P1-
C4) exhibits a nematic mesophase, which undergoes an isotropic transition at 156°C.
When the number of carbon atoms in the terminal alkyl chains of the terphenyl rigid core
increase to10 (poly (4, 4”-didecyloxy-5’-methoxy [1, 1’, 4’, 1”] terphenyl-2’-yl acrylate)

(P1-C10) and poly (1, 3-bis (4, 4”-didecyloxy-5’-methoxy [1, 1’, 4’, 1”] terphenyl-2’-
yloxy)-2-propyl acrylate) (P2-C10)), a smectic mesophase with an isotropic transition at
81.1 and 76.2 °C were observed. XRD patterns indicated a layer distance d of 21.2 Å and
18.6 Å, respectively. The results reported here demonstrated that the meophase of the
terphenyl-incorporated polymers could be manipulated by modifying the length of the
pendant alkyl groups.
A series of complexes from poly (4-dodecyloxy-2, 5-bis (pyrimidin-5-yl)-phenyl-1-yl
methacrylate) P1 and dodecylbenzenesulfonic acid (DBSA) were prepared and
characterized. In the FTIR data, the peak at 1552 cm
-1
of host polymer shifts to 1634 cm
-1

corresponding to protonated pyrimidinium ring in the complexes. DSC results showed
that only when the DBSA content in the complex is low (x = 0.5), liquid crystalline
properties with an isotropic change at 107.5 °C while a T
g
at 29.3 °C was observed. POM

159
and X-ray studies indicate that the complexes gradually lose the long order with the
increase of DBSA content. AFM results reveal that P1(DBSA)
0.5
takes a spherical
morphology in contrast to the fibrous structure of pristine polymer.
A series of novel chromophore rich polymers towards developing radiation sensitive
materials as e-beam resist were synthesized and characterized. The polymers were
characterized using FTIR, NMR spectroscopy, GPC, DSC and TGA measurements.
These polymers showed strong fluorescence emission in the region of 330 - 380 nm and
can be patterned by an electron beam in pure form or mixed with other components. All

polymers also generated intense emission in the range of 510 - 565 nm when re-
constructed by a laser source operating at a wavelength of 488 nm. The sensitivity of the
polymeric fluorescence label as an e-beam resist was also discussed.

160