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Please use this identifier to cite or link to this item: http://hdl.handle.net/1942/8857

Title: Development of a molecular spaceframe. Study towards the synthesis of molecular building blocks for this new material concept.
Authors: Van Dijk, Joachim
Advisors: Vanderzande, Dirk
Issue Date: 2003
Publisher: UHasselt Diepenbeek
Abstract: There is a permanent need for the development of new concepts and routes towards new and advanced material systems. Sometimes the macroscopic world can be used to inspire us for such new concepts. Dr. Ing. Roelof Marissen (DSM Research and Delft University of Technology, The Netherlands) suggested in 1998 investigating whether the principles of macroscopic mechanical engineering could be translated to molecular scale, provided that sufficient analogy was present between the type of molecules and the type of macroscopic structure. A very efficient macroscopic structure for mechanical strength and low density is a space frame. Space frames consist of rods, connected to each other with knots. Our ultimate interest is in the use of these molecular rods and knots as modules in the controlled construction of molecular networks and scaffolds. The construction of such structures, consisting of rigid bars (rods) which are connected via functionalized comers (knots) should result in a stiff and very strong entity as we can see, for example, in the construction of hoisting-cranes. Translation of this macroscopic principle to the molecular level should result in an isotropic polymeric material, which is very strong and stiff, and which possesses a low density. A possible advantage of this polymeric construction is its self-restoring and potentially self-healing property. Molecules, in contradiction with metal tubes, possess high elasticity, so they can return to their original structure after being twisted or buckled. The use of molecular rods as construction elements depends critically on the ability to adjust the length of the rod to a desired value, to attach the desired terminal connectors, and to ensure sufficient rigidity. Molecular rods offer the opportunity to position two knots at a known distance apart and connect them by a medium whose properties can be controlled at least to some degree. The degree of interaction between the knots can be studied and provides information about the coupling of the knots to the rod, ultimately contributing to the theory of chemical bonding. Interest in these rigid rod molecules is a phenomenon of the past decade. If we limit our horizon to well-characterized and pure individual molecular structures, very few rigid rod molecules were known before the Nineties1 ' 2 • It has been primarily driven by interest in two areas; firstly in long-distance interaction phenomena such as electron and energy transfer, magnetic coupling of transition metal atoms, etc ... and secondly in the use of molecular rods as connectors for the construction of supramolecular assemblies and giant molecules3 • Since the intention of this work was to construct a rigid molecular spaceframe, we exemplify their uses and potential uses by considering them as spacers and construction elements in giant molecules and supramolecular assemblies. To realize the purpose described above, development of some well defined monodispers rods and knots which possess high rigidity and high stiffness is essential. For this reason molecular rods may not possess flexible bonds along their axis. Flexible chains are only attached as side chains for increasing the solubility of the molecular rods. The molecular rods must also have the ability to attach in high numbers to the multifunctionalized molecular knots. Of all rigid rods known at present, oligo-p-phenylenes (A) and bisterpyridines (B) seem to be the most accessible and convenient rigid rods that could be used as rigid linkers between molecular knots.
URI: http://hdl.handle.net/1942/8857
Category: T1
Type: Theses and Dissertations
Appears in Collections: PhD theses
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