P1-0055 — Annual report 2012
1.
Optically switchable transistor via energy-level phototuning in a bicomponent organic semiconductor

In this work a semiconducting polymer was mixed with photochromic small organic molecules and the interaction between polymer and small molecules was identified as a modulation of charge transport electronic states. The work presents a plentiful set of phenomena, which can be obtained by mixing organic molecules and polymers. Moreover we present how these phenomena can be exploited in application of “multifunctional” devices. The breakthrough work explains the charge transport principles of many-component system of polymer and small organic molecules. These findings can be extended to more complex organic molecules and/or exploited to design smaller electronic devices.

COBISS.SI-ID: 2411003
2.
Osmotic pressure induced coupling between cooperativity and stability of a helix-coil transition

We analyzed the effects of osmotic pressure on the characteristics of the helix-coil transition in proteins. Our method based on an exact solution of a one-dimensional Potts model allowed us to describe the osmotic pressure dependence of the transition temperature as well as the transition interval that corresponds nicely to experimentally determined dependencies.

COBISS.SI-ID: 2453860
3.
Polar and apolar columnar phases made of bent-core mesogens

Structural studies of two-dimensionally ordered phases made of bent-core mesogens are presented, with the emphasis on the x-ray studies of the columnar phases built of smectic layer fragments. We present the evidence for two types of packing of layer fragments: the B1-type structures where layer fragments are arranged into the orthogonal body centered lattice and the B1rev-type structures made of slightly deformed layers, where the primitive crystallographic unit cell is in general oblique. In some cases two-dimensional structures made of bilayers are observed. Bilayers are characteristic for the general tilt phases, which possess longitudinal polarization component, in the direction perpendicular to the smectic layer fragment. We also outline the theoretical model predicting and describing the observed structures and give a model which enables the calculation of the electron density maps from the x-ray diffraction data.

COBISS.SI-ID: 25535015
4.
Polymers pushing polymers: polymer mixtures in thermodynamic equilibrium with a pore

We formulated a model for a nanopore penetration in a mixture of two polymer chains, one that can penetrate the pore and the other one that can not. We showed by the appropriate thermodynamic analysis that the non-penetrating polymer acts by pushing the penetrating polymer in the pore. Our conclusions are relevant for several aspects of nanotechnology.

COBISS.SI-ID: 2496868
5.
A model of epithelial invagination driven by collective mechanics of identical cells

Using a two-dimensional mechanical model, we theoretically studied gastrulation in fruit fly which begins with the formation of ventral furrow. We showed that the furrow formation can be attributed to an elastic instability of the embryonic epithelium sandwiched between the vitelline membrane and the yolk. Within our model, the only role of cell differentiation is to pin the furrow at a predetermined location. This can be achieved by a slightly increased size of mesoderm cells, which is consistent with experimental observations.

COBISS.SI-ID: 26113063