Discotic liquid crystalline materials characterized by the spontaneous formation of columns within the fluid phase display a set of interesting optoelectronic properties directly related to the state of order. The dispersion of such columnar discotics in solid polymer matrices results in geometric confinement effects controlling both the structure of the mesophase and dynamical properties related to transport properties. The confinement causes a reduction of the longitudinal and the transverse spatial correlation lengths which, in turn, gives rise to strong modifications of the absorption and emission properties as well as electronic transport processes.

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Absorption and fluorescence were investigated for liquid-crystalline discotics, which are characterized by the spontaneous formation of one-dimensional columnar structures in the fluid phase. Such materials have been considered for applications in organic light-emitting diodes and as photoconductors. We investigated materials based on asymmetrically substituted triphenylenes displaying a novel highly ordered plastic columnar state. These materials show an unexpected time dependence of the fluorescence spectrum during irradiation apparently because of their specific spatial structure. Transfer of energy from a high-energy excited state to a newly developing lower-energy state takes place. We attribute the evolution of this state to the particular spatial arrangement of the molecules within the columns in the plastic columnar state. This causes the photoinduced formation of dimers, a process that is absent in solutions and in polymer-dispersed systems of discotic materials and that has, so far, not been documented in the literature.

We have investigated the relaxation of the polar order (P1cos) in a poled styrene-maleic anhydride copolymer with side groups of modified dispersed red chromophores - using pyroelectric studies - as well as the relaxation of the orientational order (P2cos) of the optical axes of the side groups previously induced by polarized light - using holographic techniques. Isomerization cycles of the chromophores cause in the latter case the formation of an optical grating. The relaxation processes were monitored within the glassy state. In addition we investigated molecular relaxation processes, in particular the glass relaxation, using dielectric techniques. The observation was that the relaxations of the pyroelectric response and of the holographic grating couple to the glass relaxation yet do not display identical kinetics within the solid glassy state, showing that the optical grating is less stable. The difference arises obviously from the excess free volume induced by the isomerization cycle in the optical storage experiment. The formation of this excess free volume is apparent from the formation of a surface relief pattern in the storage experiment. A straightforward conclusion is that the stability of the grating can be considerably enhanced if chromophores are used characterized by a significantly lower equilibrium concentration of cis-species during irradiation.

Objective Long‐acting synthetic somatostatin analogues (SSA) are an essential part of the treatment of neuroendocrine neoplasms. We evaluated the chemopreventive effects of a long‐acting somatostatin analogue on the development of pancreatic neuroendocrine neoplasms (pNENs) in a genetically engineered MEN1 knockout mouse model. Materials and methods Heterozygote MEN1 knockout mice were injected every 28 days subcutaneously with the somatostatin analogue lanreotide (Somatuline Autogel©; Ipsen Pharma) or a placebo starting at day 35 after birth. Mice were euthanized after 6, 9, 12, 15 and 18 months, and the size and number of pNENs were measured due histological analysis and compared to the placebo group. Results The median tumor size of pNENs was statistically significantly smaller after 9 (control group vs. SSA group; 706.476 µm2 vs. 195.271 µm2; p = 0.0012), 12 (placebo group vs. SSA group 822.022 vs. 255.482; p ≤ 0.001), 15 (placebo group vs. SSA group 1192.568 vs. 273.533; p ≤ 0.001) and after 18 months (placebo group vs. SSA group 1328.299 vs. 864.587; p ≤ 0.001) in the SSA group. Comparing the amount of tumors in both groups, a significant reduction was achieved in treated Men1(+/−) mice (41%, p = 0.002). Immunostaining showed, however, no significant difference in the expression of the apoptosis marker caspase‐3, but a significant difference in Ki67 index as a marker for tumor cell proliferation (p ≤ 0.005). Conclusion Long‐acting somatostatin analogues may be an effective chemopreventive approach to delay the progression of MEN1‐associated pNENs. After our preclinical results, we would recommend to evaluate the effects of long‐acting SSA in a prospective clinical trial.