Nematic liquid crystalline mineral polymers

✍ Scribed by DR. Patrick Davidson; Jean-Christophe Gabriel; DR. Anne-Marie Levelut; DR. Patrick Batail

• Publisher: John Wiley and Sons
• Year: 1993
• Tongue: English
• Weight: 439 KB
• Volume: 5
• Category: Article
• ISSN: 0935-9648
• DOI: 10.1002/adma.19930050916

✦ Synopsis

News could, in principle, be polaron formation. However, the absence of a noticeable temperature dependence argues against this notion. Comparison with the p(T) behavior of polymeric systems above T, suggests instead a common underlying principle. It is known that molecular motion is turned on upon mesophase formation. Further, the intracolumnar structural correlation length of the system under study is of the order of 15 molecular units[231 and decreases with increasing temperature, suggesting that temperaturedriven dynamic disorder is important and controls charge transport in much the same way as it does in polymeric systems above T,. A more rigorous description of this interesting transport regime is a challenge for future theoretical work.

A by-product of the work by Adam et al. is the confirmation that polycrystalline photoconductors formed by solidification of a melt/mesophase are useless for technical application because deep traps associated with domain walls are formed that slow down transport and render it dispersive. Glass-like solidification is obviously a prerequisite for the occurrence of trap-free transport.

Photoconductivity in organic solids is an active field. Considerable progress has been made towards a better understanding of the microscopic aspects of charge transport. Nevertheless a lot of work remains to be done. For instance, no theory exists to date that allows the derivation of the density of states function of random organic systems from molecular properties.