The role of hydrogen bonds in the mesomorphic behaviour of supramolecular assemblies organized in dendritic architectures

Dendritic polymers are artificial compounds with a unique, repeatedly branched structure inspired by the respective patterns, encountered in trees. They are recognized as the fourth major macromolecular architectural class next to linear, cross linked and branched polymers. Regarding the formation of liquid crystalline phases, they follow the same rules as all the other categories. Suitable chemical functionalization induces segregation. Secondary interactions, in the form of hydrogen bonds in particular, also play a crucial role in mesophase formation by regulating polarity fluctuations and other properties such as rigidity. As a consequence, there are some cases where liquid crystallinity is attributed exclusively to the presence of hydrogen bonding networks, whereas in many more examples mesophase formation is induced mainly due to these interactions. A survey of intra and intermolecular bond influence on the liquid crystalline character of dendritic polymers is presented. The review also covers some examples of supramolecular assemblies exhibiting architecture or incorporating elements reminiscent of trees which cannot be classified as dendritic polymers where segregation resulting by hydrogen bonding is governed by the same principles. In parallel, a description of the various mesophases observed in correlation to different hydrogen bonding patterns is included, and some general conclusions and rules are suggested.