Formation of Hexagonal Columnar Mesophases by Linear and Branched Oligo- and Polyamides

The formation of columnar mesophases by N-acylated azacrown derivatives may be seen as a consequence of their discoid molecular geometry. Viewing these materials as cyclic oligomers, they are just one example of the various molecular architectures that may be realized based on the N-acylated ethylenamine fragment. By using linear oligoamides, the hexagonal columnar packing is preserved, the monotropic nature of the mesophase reflecting the higher flexibility of the systems. The corresponding polymers are accessible by polymer analogous acylation of linear poly(ethylenimine), in which a high conversion of the amino groups and a low polydispersity of the final polymers can be achieved. The resulting polyamides form enantiotropic mesophases with a hexagonal columnar structure proven by polarizing microscopy, DSC investigations, and X-ray studies. A helically folded structure of the polymer main chain is proposed whereby this structural motif is probably induced by the packing of the alkyl side chains. Based ...