Andrzej Miniewicz

Experimental and Monte Carlo studies of diffraction grating inscription in DNA-based materials

DNA-based materials offer new possibilities for holographic information inscription for photonic applications, in particular because of a very short operational time. Recent results for dynamic holographic recording/erasure of gratings in DR1:DNA-CTMA thin films are presented. We discuss the possibilities and perspectives of numerical modelling of underlying fast microscopic physical processes, in a framework of a kinetic Monte Carlo simulation method developed recently for studies of various aspects of inscription/erasure of gratings in azopolymers with doped and functionalized dyes.

Calorimetric study of the phase transitions in tris (dimethylammonium) nonabromodiantimonate (iii) and tris(dimethylammonium) nonachlorodiantimonate (III)

Abstract Temperature dependences of the specific heat of (NH2(CH3)2]3Sb2cl9 (DMACA) and (NH2(CH3)2)3Sb2Br9 (DMABA) were investigated by differential scanning calorimetry around their ferroelectric phase transitions at 242 K and 164 K, respectively. From the anomalous parts of specific heats we calculated entropy changes associated with these transitions. Transition in DMACA is an order-disorder one connected with ferroelectric type ordering of dimethylammonium cations while the transition in DMABA is also of order-disorder type but of a complex mechanism.

Application of the novel dynamic thermo-optical analysis for identification of the sequence of mesophases in thermotropic liquid crystal

ABSTRACT Identification of mesophases using a polarising microscope is vital in the area of research and development of the liquid crystal (LC) materials, however, sometimes it is very difficult to distinguish one texture from another. Here, we propose a novel method allowing for the examination of thermotropic phase sequence in polymorphic LCs called dynamic thermo-optical analysis (DTOA). In the DTOA technique the LC subjected to the cooling process is simultaneously influenced by the electric field varying sinusoidally with time. It results in the dynamic changes in the light intensity passing through the layer of such LC observed under a polarised microscope and recorded by a charge-coupled device camera. The magnitude of the changes uniquely depends on the type of the mesophase. The subsequent numerical analysis of the recorded movie (performed with a help of the image-processing software) reveals the changes in the amplitude of the average intensity of the images of the respective textures, i.e. nematic, SmA, SmC, SmI, thereby allowing for their clear identification. Furthermore, the DTOA allows to distinguish easily the SmA from the SmC phase. The azobenzene-based LC known of rich sequence of mesophases has been used here to demonstrate the principle of the DTOA method. Graphical Abstract