Research domains | Supramolecular Chemistry | Molecular Modeling | Living Radical Polymerizations | Bioacoustic | Scientific Achievements
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| Among synthetic materials, Liquid Crystals (LC) present great interest due to their unique state of matter, the mesophase, that combines two fundamental properties: order and mobility. The first results of the group have been obtained as early as 1990 and they concerned the synthesis of LC polymers with azobenzene units, as mesogenic groups, in the main chain. Polyethers and polyesters having different architectures and therefore various flexibilities were synthesised by phase transfer catalysis (PTC). The use of azobenzene is deliberate since this particular functionality can adopt two distinct configurations: (i) trans- a linear and symmetric, energetically stable conformer and (ii) cis - a non-linear and asymmetric methastable conformer. (Fig...) which can interconvert from one configuration to the another by UV irradiation by heating (cis to trans) or by exposure to visible light (trans into cis). |
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Once they are part of the polymer structural backbone, the change of azobenzene configuration will trigger conformational modification of the entire polymer chain and therefore, modifications of their packing abilities at the supramolecular level. So far more then 1500 different polymeric structures were synthesized (see below). Besides azobenzene units (DHAB), various types of bisphenols were connected using either an aliphatic (-(CH2)n-) or oxetane spacer, the latest imposing a semi-flexible geometry to the main chain. The experimental results obtained provided better insight on the correlation between the order parameter of the system, on one hand, and chain geometry and flexibility and, therefore, the intensity of interchain interactions on the other. |
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It is worth noting that the use of oxetane as a spacer imposed either a helical or linear conformation of the main chain depending on the chemical structure of the bisphenol used in the synthetic process. |
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A relatively new direction concerning the synthesis of small metallic LC molecules containing ferocenyl units was developed lately in collaboration with Prof. Dan Scutaru. (see below) |
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