Upon the solid-state degradation of poly(epsilon-caprolactone) under the action of iodine vapor, the number-average molecular weight of the polymer decreased by almost an order of magnitude 48 h after the incorporation of iodine (similar to 6 wt%) from a gaseous phase. A polymer degradation mechanism through the cleavage of C-O bonds in the polymer backbones with the formation of a charge-transfer complex involving water or polyiodide ions was proposed.

The layer-by-layer adsorption of polyethyleneimine and dextran sulfate onto the nanoparticles of biodegradable poly(D,L-lactide-co-glycolide) was conducted to produce potential delivery system of cyanocobalamin. The modified poly(D,L-lactide-co-glycolide) particles are found to be colloidal stable, nanosized with the value of hydrodynamic diameter of 210 nm and polydispersity index of 0.22. It was established that the content of cyanocobalamin absorbed by polyelectrolyte shell of the modified particles was 16 wt.

In this work, we study two series of the copolymers of L-lactide (LLA) and ε-caprolactone (CL) with the CL molar content of 5, 15, and 30 %. The first series was the commercial semicrystalline granules (Corbion, Netherlands), which we analyzed without any additional modification. The second series was amorphous films, prepared from the granules by hot pressing with the subsequent fast quenching in order to avoid the crystallization. We used Raman spectroscopy in conjunction with the quantum chemical modeling to evaluate the structure of the copolymers. As additional methods, we applied X-ray diffraction (XRD) analysis and differential scanning calorimetry (DSC). The main result of our study is the elaboration of the Raman methods of quantitative analysis of the relative contents of the comonomers and the crystallinity degree of the poly(L-lactide-co-ε-caprolactone). These methods are based on measurements of the ratios of the peak intensities of the poly(L-lactide) (PLLA) bands at 411 and 874 cm-1, the PLLA band at 2947 cm-1 and the poly(ε-caprolactone) band at 2914 cm-1. Raman study shows that growth of the CL content causes the monotonous decrease in the crystallinity degree of PLLA blocks. Density functional theory analysis of LLA decamer in the conformation of helix 103 allows us to assign the PLLA Raman bands. The Raman data on the composition and crystallinity degree of the copolymers correlate very well with the results of XRD and DSC studies, as well as with the information on the composition of the copolymers provided by manufacturer.

Lactide is one of the most popular and promising monomers for the synthesis of biocompatible and biodegradable polylactide and its copolymers. The goal of this work was to carry out a full cycle of polylactide production from lactic acid. Process conditions and ratios of reagents were optimized, and the key properties of the synthesized polymers were investigated. The influence of synthesis conditions and the molecular weight of lactic acid oligomers on the yield of lactide was studied. Lactide polymerization was first carried out in a 500 mL flask and then scaled up and carried out in a 2000 mL laboratory reactor setup with a combined extruder. Initially, the lactic acid solution was concentrated to remove free water; then, the oligomerization and synthesis of lactide were carried out in one flask in the presence of various concentrations of tin octoate catalyst at temperatures from 150 to 210 °C. The yield of lactide was 67–69%. The resulting raw lactide was purified by recrystallization in solvents. The yield of lactide after recrystallization in butyl acetate (selected as the optimal solvent for laboratory purification) was 41.4%. Further, the polymerization of lactide was carried out in a reactor unit at a tin octoate catalyst concentration of 500 ppm. Conversion was 95%; Mw = 228 kDa; and PDI = 1.94. The resulting products were studied by differential scanning calorimetry, NMR spectroscopy and gel permeation chromatography. The resulting polylactide in the form of pellets was obtained using an extruder and a pelletizer.

The kinetics of L-lactide bulk polymerization initiated with a non-toxic initiator, zirconium(IV) acetylacetonate, was studied by non-isothermal differential scanning calorimetry. The polymerization kinetics was analyzed using a combination of isoconversional "model-free" and model-fitting methods. It was revealed that the model-free analysis results in an autocatalytic reaction model function. To provide a physical meaning for this effective reaction model, a model-fitting analysis with a two-step kinetic model taking into account irreversible initiation and reversible propagation reactions was applied. It was demonstrated, that even such simple multi-step kinetic model can explain the general features of the polymerization reaction revealed by the isoconversional analysis, i. e. a variation of the effective activation energy with a conversion degree and an autocatalytic character of the effective reaction model. The rate constants for the initiation, ki, and propagation, kp, reactions were evaluated. It was revealed that the values of ki are about two decimal orders lower than that of kp indicating slow initiation in the studied temperature range.

Sixteen approximations of the density functional theory for calculating the structure and Raman spectra of the most stable α-phase of poly(L-lactide) (PLLA) with an orthorhombic crystalline lattice have been analyzed. It is shown that the GGA functionals OLYP and PBE provide good correspondence with experimental X-ray diffraction and Raman spectroscopy data. It is found that, when using extended basis sets of three- and four-exponential types, the choice of the functional affects the calculation results much more radically than the choice of the basis set.

We carried out a Raman study of a series of poly(L-lactide) (PLLA) samples annealed for different periods of time and therefore having different crystallinity degree. We compared the results with our recent study of the series of poly(L-lactide-co-ε-caprolactone) (PLCL) copolymers with the ε-caprolactone (CL) content ranging from 5 to 30 mol

Polymerization of D,L-lactide was performed in bulk at 160°C in the presence of bismuth (III) subsalicylate catalyst. Kinetics of the reaction was studied by differential scanning calorimetry in isothermal mode at 160°C and catalyst concentrations of 2500, 5000, and 7500 ppm. It was shown that the catalyst has a high activity: under this conditions an equilibrium conversion of 96% was achieved in 20–30 min, and the molecular weight of the resulting poly(D,L-lactide) reached 118 kDa.

Water-soluble nanoformulation of a hydrophobic anticancer Pt IV complex with a lonidamine-based ligand has been developed. Biodegradable nanocarriers (13 nm) obtained from poly( l -lactide-block-polyethylene glycol) star-shaped block copolymers were used to create the formulation. The loading of the active agent into nanoparticles was up to 3.7 wt.%, and the loading efficiency was up to 68%. It was shown that solubilization of the anticancer complex into polymeric nanoparticles did not lead to a significant decrease in its cytotoxicity. As the number of arms in the star-shaped block copolymers increased, the selectivity of the nanoformulations towards cancer cells tended to increase.

Degradable ureteral stent not requiring redo procedure for removal is an important issue in modern urology. This device could solve the problem of «forgotten stent» often leading to long-term complications. The authors describe the prototype of biodegradable ureteral stent based on poly(L-lactide-co-ε-caprolactone) and present the first results of its testing. Characteristics of synthesized polymer meet the requirements in medicine. Tests of rod-shaped stent prototypes showed that material has sufficient strength and elasticity. Analysis of stent degradation in artificial urine environment at 37 ºC showed that it retains strength for at least 2 weeks. No suppression of cell growth confirms no cellular toxicity. New material based on poly(L-lactide-co-ε-caprolactone) is promising for development of experimental samples of biodegradable ureteral stents and further in vivo testing.

Полилактид – биоразлагаемый полимер, который с каждым годом все более активно применяется при производстве медицинских изделий и экологолически безопасной упаковки. Актуальной задачей является поиск новых катализаторов для синтеза полилактида, которые не содержат токсичного олова и обеспечивают получение полимера с контролируемым комплексом свойств. В представленной работе синтезирован и охарактеризован каталитический комплекс на основе титана (IV). Методом дифференциальной сканирующей калориметрии исследована кинетика полимеризации L-лактида в присутствии этого катализатора, определена энтальпия реакции ((–125.1 ± 1.5) Дж/г) и рассчитаны кинетические параметры уравнения Аррениуса ( E a = (95.7 ± 7.5) кДж/моль, ln A ef = 22.7 ± 1.9).

The study of the effect of iodine on the degradation of poly(ε-caprolactone) fibers has revealed a drastic decrease in their molecular weight upon 24 h exposure to a 10% iodine solution in ethanol. It has been assumed that the main mechanism of this degradation is alcoholysis which proceeds with an efficient rate constant of nearly 7.5 × 10–3 h–1

Polylactide is a biodegradable polymer that is increasingly used in the production of medical devices and environmentally friendly packaging. The search for new catalysts for the synthesis of polylactide that do not contain toxic tin and provide a polymer with a controlled set of properties is an urgent problem. In this study, a catalytic complex based on titanium (IV) is synthesized and characterized. The kinetics of the polymerization of L-lactide in the presence of this catalyst is studied by differential scanning calorimetry (DSC), the reaction enthalpy (–125.1 ± 1.5 J/g) is determined, and the kinetic parameters of the Arrhenius equation are calculated ( E a = 95.7 ± 7.5 kJ/mol, ln A eff = 22.7 ± 1.9).

The synthesis of poly(D,L-lactide) with a predetermined molecular weight ranging from 5 to 143 kDa was conducted by ringopening polymerization of lactide in the presence of varying concentrations of the 1,12-dodecanediol activator. To synthesize poly(D,L-lactide) with COOH-end groups, polymerization was carried out in the presence of L-lactic acid. The synthesised polymer was found to contain an order of magnitude higher concentration of COOH groups than poly(D,L-lactide) synthesised in the presence of 1,12-dodecanediol.

Ring-opening polymerization of lactide was performed in the presence of 1,8-diazabicyclo[5.4.0]undec-5-ene as an organic catalyst and polyethylene glycol as a hydroxyl-containing macroinitiator. A series of amphiphilic poly(ethylene glycol-block-polylactide) copolymers with a low dispersity (PDI = 1.1), different stereoregularity and length of the polylactide block was obtained. Nanoparticles with a diameter of 20–25 nm were produced from selected polymers and were studied by in vitro cytotoxicity tests.

Dermal fillers have gained significant attention in the field of aesthetic medicine due to their ability to restore volume and correct facial wrinkles. Even though such formulations have similar compositions, they can have different microstructure and molecular characteristics, which in turn affect the biodegradation profile. This study presents the results of an investigation of the physicochemical characteristics of four dermal fillers from different manufacturers (Sculptra®, Gana V®, AestheFill®, and Repart PLA®). The molecular and supramolecular characteristics of polylactic acid (L/D isomer ratio, molecular weight, degree of crystallinity), the morphology and size of PLA microparticles were determined. Hydrolytic degradation studies in phosphate buffer revealed differences in the rate of molecular weight reduction in the polymer. The obtained data may be important for the analysis and interpretation of the results of biological studies and clinical outcomes of the PLA dermal fillers.

The purpose of this work is to theoretically and experimentally investigate the applicability of the Tsai-Hill failure criterion and classical laminate theory for predicting the strength and stiffness of 3D-printed polylactide laminate composites with various raster angles in mechanical tests for uniaxial tension and compression. According to the results of tensile and compression tests, the stiffness matrix components of the orthotropic individual lamina and strength were determined. The Poisson's ratio was determined using the digital image correlation method. It was found that the Tsai-Hill criterion is applicable for predicting the tensile strength and yield strength of laminate polymer composite materials manufactured via fused deposition modeling 3D printing. The calculated values of the elastic moduli for specimens with various raster angles correlate well with the values obtained experimentally. In tensile tests, the error for the laminate with a constant raster angle was 3.3%, for a composite laminate it was 4.4, in compression tests it was 11.9% and 9%, respectively.

The main goal of research is to study ring-opening polymerization of L-lactide in the presence of multifunctional alcohols in order to determine the optimal conditions for synthesis of star-shaped molecules of a predetermined well-defined structure, which is necessary for fine adjustment of material properties for various biomedical applications. The degree of polymerization of 3-, 4- and 6-arm star-shaped poly(L-lactides) varied from 10 to 100 monomer units per arm. It was found that under the same conditions polymerization rate and rate of initiation of co-initiator's hydroxyl groups can vary significantly depending on the structure and concentration of the selected alcohol. To prove the absence of cyclic, linear and comet-like structures in synthesized star-shaped PLLA, a variety of instrumental methods were used including GPC with triple detection, 1H NMR and MALDI. Study of properties and supramolecular structure of poly(L-lactides) using DSC and WAXS demonstrated that branching limits segmental mobility of the PLLA chains, especially for short arms, and hinders crystallization of star-shaped poly(L-lactides).

Biocompatible, biodegradable polymers are actively used as drug delivery systems and as tissue engineering scaffolds. The hydrothermal aging of polymers, including degradation of the microstructure and changes of mechanical properties directly depends on environmental conditions. In vitro studies in a model media cannot contain and describe all the factors influencing the polymer degradation in a living organism. It seems promising to study the processes of changes in the microstructure and elastic properties of polymer implants in vivo in dynamics. Here, we present data from the application of new experimental equipment for high-resolution ultrasound imaging of polymer degradation in vivo. Ultrasonic results include images of the transformation of volumetric microstructure and changes in elastic properties in dynamics. The method was verified on a rapidly degradable polymer poly(D,L-lactide-co-glycolide). We assess and compare the evolution of volume microstructure, elastic properties and molecular weight of the polymer weekly for 1.5 months of incubation in vitro and in vivo. We found that the in vivo degradation process occurs with a delay of 2 weeks compared to the hydrothermal aging in vitro.