Vitaliy Gomzyak

Various hydroxyapatite-filled and unfilled microspheres based on lactide and glycolide copolymers were prepared. The synthesized poly(lactic-co-glycolic acid) (PLGA) samples were characterized by GPC and ¹H NMR spectroscopy, the morphology was characterized by SEM. It was shown that under the tin (II) 2-ethylhexanoate catalysis the glycolide is highly active in copolymerization as compared with lactide. According to the data on weight loss and the weight average molecular weight shift of PLGA over time (pH = 6.5; t = 25 °C), an increase in the rate of microsphere destruction was noted when macromolecules were enriched with glycolic acid residues, as well as when filled with hydroxyapatite. It was shown that the rate of PLGA degradation was determined by the water-accessible surface of a sample. The rate increase in PLGA hydrolytic degradation both with an increase in glycolic acid residues mole fraction in the chain and upon filling with hydroxyapatite was the result of the microspheres’ surface hydrophilization, an increase in capillary pressure upon filling of the pores as well as of the defects with water, and an increase in the number of structural defects. Approaches to the creation of composite microspheres based on PLGA degrading at a controlled rate were proposed.

The combination of biocompatibility, biodegradability, and high mechanical strength has provided a steady growth in interest in the synthesis and application of lactic acid-based polyesters for the creation of implants. On the other hand, the hydrophobicity of polylactide limits the possibilities of its use in biomedical fields. The ring-opening polymerization of L-lactide, catalyzed by tin (II) 2-ethylhexanoate in the presence of 2,2-bis(hydroxymethyl)propionic acid, and an ester of polyethylene glycol monomethyl ester and 2,2-bis(hydroxymethyl)propionic acid accompanied by the introduction of a pool of hydrophilic groups, that reduce the contact angle, were considered. The structures of the synthesized amphiphilic branched pegylated copolylactides were characterized by ¹H NMR spectroscopy and gel permeation chromatography. The resulting amphiphilic copolylactides, with a narrow MWD (1.14–1.22) and molecular weight of 5000–13,000, were used to prepare interpolymer mixtures with PLLA. Already, with the introduction of 10 wt% branched pegylated copolylactides, PLLA-based films had reduced brittleness, hydrophilicity, with a water contact angle of 71.9–88.5°, and increased water absorption. An additional decrease in the water contact angle, of 66.1°, was achieved by filling the mixed polylactide films with 20 wt% hydroxyapatite, which also led to a moderate decrease in strength and ultimate tensile elongation. At the same time, the PLLA modification did not have a significant effect on the melting point and the glass transition temperature; however, the filling with hydroxyapatite increased the thermal stability.

The review presents modern advances in the synthesis of biodegradable polymers based on lactide of various topologies and also analyzes the main methods for preparation of nanoparticles that show promise for the creation of targeted drug delivery systems.

This paper presents data on styrene polymerization in emulsions stabilized by biodegradable poorly water-soluble polyester polyol of 2,2-bis(methylol)propionic acid (polyester Boltorn H40). The effect of synthesis conditions on the kinetic laws of polymerization is studied. The results are analyzed in comparison with those previously obtained under similar conditions but in the presence of water-soluble surfactants.

Objectives. Biologically active polymeric surfactants are a new promising class of macromolecules that can find application in medicine, cosmetology, and agriculture. In this study, a number of new biologically active amphiphilic polymers based on branched silatrane-containing polyesters and polyethers were obtained, and their surface-active properties were investigated.Methods. The branched polymers were represented by polyethers and polyesters, obtained respectively via the anionic polymerization of 1,2-epoxypropanol or a combination of equilibrium polycondensation and ring opening polymerization. The polymers were modified with 3-isocyanopropylsilatrane and trimethylethoxysilane to obtain the amphiphilic compounds containing silatrane groups bonded to the polymer backbone by the urethane bond. The structure of the synthesized polymer silatranes was confirmed via nuclear magnetic resonance spectroscopy and gel permeation chromatography. The surface active properties of all the copolymers obtained were investigated in connection with their obvious amphiphilicity. In particular, the formation of micelles in aqueous solutions is such a property. The critical micelle concentrations were determined by a method of quenching the fluorescence of the polymers.Results. It was shown that the values of the critical micelle concentrations and the hydrophilic-lipophilic balance values of polymers determined by the Griffin equation correlate well with each other. A linear relationship between the hydrophilic-lipophilic balance and the critical micelle concentrations was established. At the same time, polyether-based polymers generally showed higher critical micelle concentrations than polyester-based polymers, although the hydrophilic-lipophilic balance values for polymers of different series, but with close degrees of substitution, were close. It was found that the use of all synthesized polymers as stabilizers of direct and reverse emulsions leads to an increase in the aggregative stability of both types of emulsions. The stability of emulsions depended both on the degree of substitution of peripheral hydroxyl groups of polymers by silatranes and on the molecular weight and structure of the branched block of polymers. The stability of direct emulsions increased for all polymers, while that of inverse emulsions decreased with an increasing degree of substitution of hydroxyl groups by silatranes. The increase of the branched block molecular weight led to an increase of droplet sizes for both direct and inverse emulsions. The smallest droplet size for direct and inverse emulsions was obtained using polymers with low molecular weight branched polyester blocks as surfactants.Conclusions. The results obtained prove the possibility of creating polymer surfactants containing silatrane groups. By varying the structure of the polymer, its molecular weight and the degree of substitution of peripheral functional groups, it is possible to obtain surfactants with desired surface properties.

The possibility of synthesizing silatrane-containing polymers was investigated using three different synthetic methods: the formation of silatrane fragments from polymers with trialkoxysilyl groups, the copolymerization of silatrane-containing monomers, and the reaction of silatranes with functional copolymers. The obtained polymethacrylate copolymers were characterized using gel permeation chromatography, IR and NMR spectroscopy. It was shown that depending on the synthesis scheme used, polymers were obtained in the form of three-dimensional structures or soluble products. It was established that the molecular weight of the synthesized polymers depended significantly on both the content of silatrane fragments and the synthesis technique used. It was shown that the modification of linear carboxyl-containing copolymers by silatranes allows the synthesis of high-molecular polymers with a high content of silatrane fragments. For the synthesized polymers, thermal properties were investigated, and the hydrophobicity of the surface of polymer films was also evaluated. It was found that all the studied polymers did not have clear melting and crystallization temperatures. The polymers were stable in an inert atmosphere up to 270-280 °C, whereas in air they decomposed at lower temperatures with the restructuring of the macromolecular skeleton and the formation of highly heat-resistant silicone structures. An increase in the content of silatrane moieties in the copolymers led to an increase in the hydrophilicity of polymers.

Синтетические поверхностно-активные вещества широко используются в самых различных отраслях - от медицины до сельского хозяйства, причем повышенный интерес представляют биодеструктируемые ПАВ. Перспективными соединениями для синтеза таких ПАВ являются полиэтиленоксид и сложные полиэфиры α-гидроксикислот: полилактид, полигликолид, поли(ε-капролактон), полигидроксибутират, а также их сополимеры. Поскольку продуктами деструкции таких полимерных ПАВ являются естественные метаболиты, их применение в медицине и биотехнологии довольно перспективно. В ряде работ показаны преимущества полимерных сверхразветвленных ПАВ по сравнению с линейными ПАВ, однако систематические исследования взаимосвязи структуры амфифильных сверхразветвленных ПАВ с их поверхностной активностью отсутствуют. Сверхразветвленные биоразлагаемые полиэфирполиолы на основе 2,2-бис(метилол)пропионовой кислоты широко используются в качестве модификаторов полимерных материалов (например, при производстве лакокрасочных материалов), добавок к полимерам для улучшения экструзии, а также в качестве наноконтейнеров для адресной доставки лекарственных соединений. В настоящей работе изучены коллоидно-химические свойства полиэфирполиола 2,2-бис(метилол)пропионовой кислоты четвертой псевдогенерации (торговое имя Boltorn H40) и показано, что данное соединение обладает поверхностно-активными свойствами и снижает межфазное натяжение на границе углеводородный раствор ПАВ/вода до низких значений.