Mesomorphism from bent-core based ionic dendritic macromolecules

Abstract

A wide variety of ionic dendritic macromolecules based on bent-shaped structures have been synthesized and fully characterized. Regular polypropyleneimine dendrimers (PPI) of different generations and a random hyperbranched polymer (PEI) were selected as dendritic cores. Different bent-core structures derived from the 3,4′-biphenyl angular core with 5 or 6 aromatic rings as well as short and long terminal chains and spacers have been used for this study. The bent-core structure acts as strong driving force for the supramolecular arrangement of this type of macromolecules. All of the ionic dendritic polymers prepared show mesogenic behavior over broad temperature ranges, even if the carboxylic acid precursors were not mesomorphous. An extensive chemical structure-supramolecular organization relationship has been proposed for first time for this kind of bent-core dendrimer. Two types of supramolecular packing with lamellar and columnar order have been proposed on the basis of polarizing optical microscopy, differential scanning calorimetry, and X-ray diffraction. Additionally, fibers that present anisotropic optical behavior can be drawn from the materials. These results open new and stimulating possibilities for both bent-core based and dendritic supramolecular systems, with interest in basic and applied supramolecular chemistry and materials science scenarios. © 2011 American Chemical Society.