M. Lee et al., Linear rod-coil multiblock oligomers with a repeating unit-dependent supramolecular organization, MACROMOLEC, 34(6), 2001, pp. 1987-1995
A series of linear rod-coil multiblock oligomers of the (rod-coil)(n) type
(n = 1, 2, 3, 13) consisting of a rigid rod segment made up of three biphen
yls connected though methylene ether linkages and a poly(propylene oxide) w
ith degree of polymerization of 13 as a coil segment were prepared, and the
ir thermal behavior and supramolecular organization in the solid and melt s
tates were investigated. In opposition to the behavior of conventional olig
omers, transition temperatures of these multiblock oligomers associated wit
h both crystalline melting and isotropization decrease With increasing the
number of repeating units (n). Small- and wide-angle X-ray diffraction inve
stigations were carried out to elucidate the details of supramolecular stru
cture. All of the oligomers were observed to be self-organized into ordered
supramolecular structures that differ significantly on variation of the nu
mber of repeating units. The (rod-coil)(1) shows a lamellar crystalline and
a bicontinuous cubic liquid crystalline structures. In contrast, the (rod-
eoil)(2) shows a 2-D rectangular crystalline and a tetragonal columnar liqu
id crystalline structures, while the (rod-coil)(3) and the (rod-coil)(13) d
isplay a hexagonal columnar structure in both their solid and melt states.
These results demonstrate that systematic variation of the number of repeat
ing units in the rod-coil multiblock oligomers can provide a strategy to re
gulate the supramolecular structure, from 1-dimensional lamellar, a-dimensi
onal rectangular to 2-dimensional hexagonal structures in the solid state a
nd from bicontinuous cubic, tetragonal columnar to hexagonal columnar in th
e melt state.