Microphase separation in block cooligomers based on a discotic liquid-crystalline block

Block cooligomers of 2,6,7,10,11-pentapentyloxy-3-(3-acryloylpropyloxy)triphenylene and poly(tert-butyl acrylate) have been synthesized by the atom-transfer living radical polymerization. The preformed 3,6,7,10,11-pentapentyloxy-3-(3-acryloylpropyloxy)triphenylene block comprising eight monomer units was used as a macroinitiator with a fixed length, whereas the length of the poly(tert-butyl acrylate) block was varied through a change in the monomer-to-macroinitiator ratio. The microphase separation phenomenon has been established with DSC and X-ray diffraction. However, the sizes of discrete structures observed via transmission electron microscopy and atomic-force microscopy lie in the micron-size length (0.1-3.0 mu m). This fact is inconsistent with the molecular characteristics of individual blocks. It is proposed that the micron-sized structural elements are not true domain structures belonging to each phase but reflect the occurrence of aggregation in solution preceding formation of thin films.