Synthesis and Properties of Ethylene/propylene and Ethylene/propylene/5-ethylidene-2-norbornene Copolymers Obtained on Rac-Et(2-MeInd)2ZrMe2/Isobutylaluminium Aryloxide Catalytic Systems

Ethylene/propylene (E/P) and ethylene/propylene/5-ethylidene-2-norbornene (E/P/ENB) copolymers were obtained on rac-Et(2-MeInd)2ZrMe2 activated by a number of isobutylaluminium aryloxides: (2,6-tBu2PhO-)AliBu2 (1-DTBP) (2,6-tBu2,4-Me-PhO-)AliBu2 (1-BHT), (2,4,6-tBu2PhO-)AliBu2 (1-TTBP), (2,6-tBu2,4-Me-PhO-)2AliBu (2-BHT), (2,6-tBu2PhO-)2AliBu (2-DTBP), [(2-Me,6-tBu-C6H3O)AliBu2]2 (1-MTBP), [(2,6-Ph2-PhO)AliBu2]2 (1-DPP). This study shows how the structure of an activator influences catalytic activity and polymer properties, such as the copolymer composition, molecular weight characteristics, and thermophysical and mechanical properties. It has been shown that both the introduction of a bulky substituent in the para-position of the aryloxy group and the additional aryloxy group in the structure of an activator lead to a significant decrease in activity of the catalytic system in all studied copolymerization processes. Moreover, activation by bulkier aryloxides leads to lower levels of comonomer insertion and gives rise to higher molecular weight polymers. Broad or multiple endothermic peaks with different values of melting points are observed on the DSC curves of the copolymers obtained with different catalytic systems. The DSC of the thermally fractionated samples makes it possible to reveal the heterogeneity of the copolymer microstructure, which manifests itself in the presence of a set of lamellar crystallites of different thickness. The results also present the mechanical properties of the copolymers, such as the tensile strength (σ), elongation at break (ε), and engineering strain (EL). The synthesized E/P and E/P/ENB copolymers contain about 1–4 wt.% of the sterically hindered phenols obtained in situ as a residue of the hydrolyzed activators in the course of reaction quenching. This determines the increased thermooxidative stability of the copolymers

Polyelectrolyte Microcapsules as a Tool to Enhance Photosensitizing Effect of Chlorin E6

Introduction: Photodynamic therapy is a promising method of tumors treatment using photosensitizers and light of a certain wavelength. PS modification improves and enhances the phototoxic effect with decreased dark cytotoxicity. Materials and Methods: We compared the photosensitizing effect of polyelectrolyte microcapsules with chlorin E6 (ClE6) and free ClE6 at equivalent concentrations on murine fibroblast culture L929 using in vitro tests. Microcapsules were prepared layer by layer, sequentially depositing oppositely charged polyelectrolytes onto spherical CaCO3 particles. Cellular uptake of capsules was assessed using confocal microscopy. MTT test was used for a study of cell viability, and the relative amount of ROS was determined by the fluorescent method. Results: Microcapsules with ClE6 (in all tested concentrations) after exposure to red light (660 nm) reduced cell viability from 20% to 5%, while these capsules did not have dark cytotoxicity. Free ClE6 at the same concentrations as in the capsules after irradiation reduced viability from 65% to 35%. The level of ROS in the group of cells with capsules was 2 times higher compared to the group with CLE6. Discussion: The most probable mechanism of toxicity increase is creation of a higher ROS concentration and effect localization in the area of microcapsule interaction with the cell membrane. ROS production activation may stem from capsules providing a higher local PS concentration in the cell or nearby than the drug’s free form. Conclusion: The inclusion of chlorin E6 in polymer capsules reduced dark toxicity and increased the photosensitizing effect compared to the free form of ClE6