University of Birmingham > Talks@bham > Condensed Matter Physics Seminars > Structure of liquid crystalline dendrimers

Structure of liquid crystalline dendrimers

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  • UserProf. Rob Richardson, Bristol University
  • ClockFriday 10 December 2010, 14:00-15:00
  • HousePhysics East 217.

If you have a question about this talk, please contact Elizabeth Blackburn.

The talk will outline recent investigations of the structure of carbosilane Liquid Crystal dendrimers synthesised by the group of Professor Shibeav in Moscow. These materials are made by joining elongated mesogenic units to the extremities of a dendritic core. X-ray diffraction from magnetically aligned samples will be presented for dendrimers with generation numbers up to five. It is found that increasing the generation number changes the molecular packing, driving the phase structure from lamellar to columnar. Low generation numbers favour simple smectic structures while higher generations show the formation of in-plane columns. The nature of these columnar phases has been elucidated by diffraction at non-ambient pressure.

Neutron scattering has also been used to investigate the nature of dendrimer liquid crystals. Small angle neutron scattering (SANS) from solutions in toluene has been used to determine the size of single dendrimer molecules. The SANS from the pure dendrimers in their Liquid Crystal phases reveal an unusual segregation effect. Large, anisotropic regions (~100nm x 20nm) are formed. This has been investigated by comparing the scattering from normal hydrogenous and deuterated versions of the liquid crystal dendrimers. It was deduced that the segregation is due to structural inhomogeneity and recent mass spectroscopy results have supported this. It is concluded that there is incomplete reaction between the dendritic core and the mesogenic units.

This talk is part of the Condensed Matter Physics Seminars series.

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