Molecular hybrid architectures

Figure 1.2 Four major small molecular architectures derived from the hybridization states of carbon...

As this brief overview demonstrates, novel copolymers obtained by hybridization of the linear and globular architectural states are readily prepared through a variety of synthetic approaches. In general the dendritic components of the hybrid copolymers are well defined, with unique molecular and structural characteristics. In contrast, all the linear components prepared polymerization are less precisely defined and are polydisperse. Only the very short linear components, themselves prepared by stepwise synthesis just like the dendrons, are monodisperse and can be used to prepare well-defined, monodisperse hybrids. While architectural and structural precision may be of great importance for the determination of ultimate properties, some degree of structural variation is quite acceptable for practical applications in many areas including, for example, surface modification, sensing, or encapsulated delivery. 

It is clear that the combination of different architectures and the precise localization of functionalities within a single macromolecule provide unique opportunities for the control of molecular shape as well as molecular, optical, and electronic properties. A significant hurdle that still remains today is the relatively demanding multistep process used to prepare dendrons and hybrids. This, in turn, translates into limited availability but, as high added-value applications emerge, it is clear that current, as well as yet-to-be-developed, syntheses will be used to prepare specialty materials that benefit from the unique properties derived from the combination of dendritic and linear architectures. 

Metallacalixarenes Organo-lnorganic Hybrid Molecular Architectures... 

S. Kumar, N. Kaur, and H. Singh (Guru Nanak Dev University, Amritsar, India) have followed up their review entitled Syntheses, Structures and Interactions of Heterocalixarenes in Volume 89 of Advances in Heterocyclic Chemistry with a new consideration of metallacalixarenes and their organo-inorganic hybrid molecular architectures. 

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