The synthesis and the characterization of rigid-rod polyesters 2 and 3 deriving from 2',5'-dihexyl-pterphenyl-4,4"-diol 7 and from 2',5'-dihexyl-p-terphenyl-4,4"-dicarboxylic dichloride 8 together with a facile synthesis of monomers 7 and 8 is described. It is shown that these polyesters exhibit a very good solubility in common organic solvents. Therefore these materials present interesting model compounds for comprehensive studies of rigid-rod polymers in solution.
The analysis of the conformation of a stiff-chain polyester by
magnetic birefringence is
presented. The specific Cotton−Mouton constant,
C
2
b, has been measured for five
different molecular
weights of the polyester. A general analysis of the data is
presented, including the effect of polydispersity.
A weak dependence of C
2
b on
molecular weight is found, which shows that the persistence length of
the
polyester is approximately 11 nm. Estimates of the specific
Cotton−Mouton constant per unit length by
using group increments compare favorably with the measured
value.
Cotton-Mouton constants mC of nematogenic oligomers of the oxybenzoate series have been determined in solution. The experimental values of mC were compared with the Cotton-Mouton constant calculated from group additivity schemes: For the tensor of the diamagnetic susceptibility, the scheme of Flygare (Chem. Rev. 1974,74,653) was used, and for the polarizability tensor group, contributions deduced previously from depolarized Rayleigh scattering (DRS; J . Phys. Chem. 1990,94,3215) were employed. Good agreement of measured and calculated & values is found. The influence of the local field correction used for the evaluation of both the DRS and the Cotton-Mouton constant is discussed.
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