Due to their highly branched structure and the large number of functional groups hyperbranched polymers possess unique properties that make them interesting for uses in a wide variety of applications. Some of the most widely investigated hyperbranched polymers are the polyesters based on 2,2-bis(methylol)propionic acid. In this paper we present the results of characterization studies of hyperbranched polyesters based on 2,2-bis(methylol)propionic acid which show that they are very complex products with a multidimensional distribution of various properties. The influence of the synthesis conditions on the structure and molar-mass characteristics of hyperbranched polyesters as well as the findings that allow a thorough understanding of the structure-property relationships are reviewed in detail.
COBISS.SI-ID: 4487194
Solid dispersions of glimepiride, belonging to the sulfonylurea group of antidiabetic drugs, and poly(ester amide) hyperbranched polymers of different chemical compositions were prepared in order to improve glimepiride's poor water solubility. X-ray powder diffraction results show that glimepiride is in noncrystalline form, indicating that drug molecules are molecularly dispersed within the amorphous hyperbranched polymers. Nuclear magnetic resonance spectroscopy and Fourier transform-infrared spectroscopy results reveal the complex formation between the glimepiride drug and the particular hyperbranched polymer, which was confirmed also by quantum chemical calculations. The complex is stabilized by a hydrogen-bond interaction between the NH group of the sulfonylurea segment of glimepiride and the carbonyls of the amide and ester bonds of the hyperbranched polymers. The slightly acidic proton of the NH group of the sulfonylurea segment of glimepiride is also involved in an interaction with the tertiary amino functional groups of the hyperbranched polymer. As a consequence, the loading capacity is higher for the hyperbranched polymer with the tertiary amino groups. Owing to a complex formation between glimepiride and a particular hyperbranched polymer, glimepiride's water solubility and its dissolution rate are considerably improved relative to the pure glimepiride drug.
COBISS.SI-ID: 4713498
Spherical ZnO nanoparticles were synthesized via a simple one-pot synthesis route by refluxing an oversaturated solution of zinc acetylacetonate hydrate in tert-butanol. A reaction occurs via a ligand-exchange mechanism, i.e., the dissociation of the acetylacetonate group from the zinc centre. The formation of ZnO is slow because of the low nucleophilicity, boiling point and dielectric constant of the medium. The single-crystal ZnO nanoparticles develop near the precursor surface until they reach a critical size and, once diffused into the medium, do not agglomerate, but retain their size and morphology.
COBISS.SI-ID: 4765210