Aziz M. Muzafarov

Nanostructured organosilicon luminophores as a new concept of nanomaterials for highly efficient down-conversion of light

Nanostructured organosilicon luminophores (NOLs) are branched molecular structures having two types of covalently bonded via silicon atoms organic luminophores with efficient Förster energy transfer between them. They combine the best properties of organic luminophores and inorganic quantum dots: high absorption cross-section, excellent photoluminescence quantum yield, fast luminescence decay time, good processability and low toxicity. A smart choice of organic luminophores allowed us to design and synthesize a library of NOLs, absorbing from VUV to visible region and emitting at the desired wavelengths from 390 to 650 nm. They can be used as unique wavelength shifters in plastic scintillators and other applications.

Adsorption properties of pyridylphenylene dendrimers

Here we report a sorption and surface properties study of the first three generations of polypyridylphenylene dendrimers. A BET analysis of N2 adsorption/desorption isotherms at 77 K yielded specific surface area values not exceeding 100 m2 g−1, while theoretical estimates predicted large pore volumes and surface areas of thousands of square meters per gram. By means of MD simulations, we showed this difference to be due to the close packing of dendrimers in bulk. T-plot and BJH analyses revealed the mesoporous character of the studied systems, with pore sizes comparable to the diameters of the individual dendrimer molecules. The measured adsorption/desorption isotherms of water vapor on dendrimer generations 1 and 3 implied a chemisorption process involving the formation of hydrogen bonds.

Chapter 8 – Organosilicon Dendrimers and Irregular Hyperbranched Polymers

Abstract Available data as regards the properties of organosilicons—dendrimers, hyperbranched polymers, and nanogel particles on their base—are analyzed. The study of the properties of dendrimers, comparison of their behavior in solutions and in block with irregular hyperbranched polymers, make it possible to characterize these objects and ascertain the influence of differences in regularity as well as to better comprehend the very notion of macromolecule-particle, with the phenomenological model of “macromolecule” to “particle” transition. Such macromolecular nano-objects are really a special form of organization of polymer substance and have vivid peculiarities in manifestation of their properties. It is reasonable to consider them as a separate specific group of polymer systems in terms of the main chain structure. The most interesting and promising objects are siloxane nanogels. Changes taking place in these macromolecules are unique in terms of combination of “polymeric” characteristics and properties of solid particles that is quite amenable to control in accordance with a particular task. It was found that transformation of the object properties is caused by the core compaction and alteration of the core-to-shell ratio in its structure; it takes place gradually, the increase in molecular mass has little effect on changes in these properties. At the same time the transition of quantitative changes in the molecular structure into qualitative in dendrimers and multiarm stars occurs abruptly, that is, in particularl those cases where an abrupt change of the molecular parameters occurs. The qualitative changes taking place in dendrimers, multiarm stars, and dense molecular brushes, first in siloxane nanogels, significantly extend a possibility of creating new materials, and deserve our attention. The potential of their practical application is highly dependent on the depth of our understanding of the “structure-properties” relationship for each type of nano-objects.