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Sunday, September 9, 2012

‘A Textbook of Nanoscience and Nanotechnology’ by T. Pradeep

Dendritic nanostructures

"Dendrimers are categorised as macromolecules. A molecule is labelled as macromolecule based on its size. In Greek, macros means large. The word, macromolecule, was first coined by Staudinger to refer to molecules with molecular weight higher than 10,000. Macromolecules receive significant attention due to their unique chemical as well as material properties. Also, bio-macromolecules, such as carbohydrates, proteins and nucleic acids, play vital role in our lives. Nonetheless, systematic studies of structure-property relations are lacking in many important macromolecular systems. Since macromolecules are relatively larger in size compared to other organic molecules, the size range falls into the 'nano' regime, whereas the size of small organic molecules fall in 'angstrom' size range (an order of magnitude less than nano). Thus, macromolecules constitute 'nano' organic systems, having numerous applications in material chemistry. Until early 1980s, chemists were familiar with different types of polymeric systems as synthetic macromolecules, where each monomer was added to the backbone of the polymer chain to form a large structure of linear assembly. Later, another class of macromolecules was developed in laboratories, where the 'monomers' were added to one core unit with further possibility of branching out to the periphery in a globular fashion. They were structurally different from conventional polymers, and were associated with certain distinct properties. A scientist, named Donald A. Tomalia from USA, named this class of molecules as 'dendrimers' due to their resemblance with highly-branched trees ('dendros' in Greek means 'branch or tree' and 'meros' means 'part'). While the origin of dendrimers was received with much scepticism among scientists, it was later proved beyond doubt that they can be efficiently synthesised in chemical laboratories and can be characterised with routine spectroscopic techniques, such as NMR, Mass and IR."

(pp. 475-6, 'A Textbook of Nanoscience and Nanotechnology' by T. Pradeep – TMH)

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