Synthesis of new type of dendritic molecule and its columnar self-assembly having a potential as molecular cavity

In this study, we synthesized the first generation aromatic polyamide dendron having one trioxyethylene chain at the top of the dendron and six octadecyl chains at the other terminals. This material forms two types of crystals, K1 and K2 crystals. The K1 crystal is obtained on cooling from the isotropic melt at a normal rate, while the K2 crystal grows only when the isotropic melt is retained at around 70 °C for long duration, i.e. 1 day. The K2 crystal melts at 78 °C which is higher than 59 °C of the K1 crystal, and has a well-defined packing structure with a huge hexagonal lattice (a=b=69.8 and c=4.24 Å) that includes five molecules. Such a characteristic hexagonal structure is produced by a columnar association of molecules, in such a way that five molecules aggregate to form a disk, the disks are stacked into a column and the columns are packed into a hexagonal lattice. The microsegregation of chemically different components is responsible for the columnar association of molecules since in this column aromatic groups construct the cylindrical core tube with hydrophilic trioxyethylene chains inside and hydrophilic alkyl tail groups outside the tube.