Aqueous solution behaviour and solubilisation properties of octadecyl cationic gemini surfactants and their comparison with their amide gemini analogues.

Gemini surfactants 18-s-18(Et), comprised of two ethylammonium headgroups and two alkyl tails with m = 18 carbon atoms with spacers of s = 4, 6, 8 and 10 linking the headgroups (alkanediyl-α,ω-bis(diethyloctadecylammonium bromides)), were obtained. Their aqueous solution behaviour, including adsorption at the interface and aggregation in solution, was followed by tensiometric, conductometric and spectroscopic methods. The critical micelle concentration (CMC) of the surfactants decreased with increasing spacer length. The size of 18-s-18(Et) aggregates formed at concentrations of 10 and 40 CMC measured by DLS varied with the elongation of the spacer. Visualisation of aggregated surfactant structures at 40 CMC by cryo-TEM evidenced the formation of different morphologies depending on spacer length. Gemini with s = 4 formed elongated, cylindrical micelles, while geminis of s = 6, 8 and 10 self-assembled into vesicles. The ability of the studied geminis to solubilise hydrophobic dye Sudan I in water was determined as a function of surfactant concentration, demonstrating their high efficiency. Results for 18-s-18(Et) geminis were compared with those previously obtained for their analogues containing an amide group placed between headgroups and tails. The significant impact of amide groups on the surface activity and aggregation properties of gemini surfactants was evidenced and is related to hydrogen-bond formation by amide-containing compounds.

Designing bioresorbable polyester matrices for controlled doxorubicin release in glioma therapy.

The influence of the chain microstructure on release process of doxorubicin from polymeric matrices was analyzed. Aliphatic polyester copolymers with optimal chain microstructure, i.e. poly(glycolide-co-L-lactide, 15/85) (PGLA) and poly(glycolide-co-epsilon-caprolactone, 10/90) (PGCA) were synthesized for long-term doxorubicin delivery systems. Various release profiles from PGLA and PGCA matrices were obtained. The investigations revealed the most steadily doxorubicin release from PGCA matrices with 5% (w/w) of drug content. Degradation of matrices with and without drug was monitored by means of NMR spectroscopy and confirmed stability of degradation process. From PGCA matrices the increase of released doxorubicin amount was observed during first 60 days. On the contrary in case of matrices obtained from PGLA the delay of doxorubicin release was observed during first 50 days, what was caused by interaction of drug molecules with polylactide chain of polymer matrix. The interaction between doxorubicin molecules and polylactide chains was confirmed by IR spectroscopy. This fact can be used for designing of delivery systems consisting of combination of matrices with different microstructure of copolymer chains in order to adjust concentration of released doxorubicin and stabilization of drug release process.

Characteristic and spectroscopic properties of the Schiff-base model compounds.

Two series of conjugated aromatic imines (Schiff-base model compounds) with different central groups and various side-group substitutions have been synthesized and characterized by elemental analysis, differential scanning calorimetry (DSC) technique, hydrogen nuclear magnetic resonance ((1)H NMR), Fourier transform infrared (FTIR) and ultra-violet and visible light (UV-vis) spectroscopy measurements. The UV-vis absorption of solutions of these compounds in dimethylacetamid (DMA), chloroform and methanol was investigated in the optical range from 240 to 450nm, where two distinct absorption bands: at 250-280 and 315-360nm with the different level of absorption have been observed. The influence of compound molecular structure and polarity of solvent on the absorption spectra and the possible optical transitions have been discussed. Structure of diamines in the azomethine models fundamentally affected their spectroscopic properties and conjugation of pi-electrons.

Infrared study of chlorophenols and products of their photodegradation.

The presents study of the 3-chlorophenol, 2,4-dichlorophenol, 2,3,4,5-tetrachlorophenol, pentachlorophenol and products of their photodegradation using FT-IR spectroscopy and GC/MS. Spectra of pure chlorophenols with the spectra of their solutions after photodegradation were compared. FT-IR spectra of pure chlorophenols investigated in the region of 3700-3000cm(-1) show that in particular cases the position and shape of bands corresponding to stretching vibration of hydroxyl groups are different. In all cases, the differences between spectra of pure chlorophenols and irradiated solutions were observed. It was confirmed that different distribution of types of hydrogen bonds appearing in particular chlorophenols has strong influence on the process of irradiation reaction and final products.

Investigation of infrared calibration methods for application to the study of methyl methacrylate polymerization.

Infrared spectroscopy has been used to monitor the polymerization of methyl methacrylate. Concentrations of methyl methacrylate in the reaction mixture were determined by use of three calibration methods. Classical quantitative analysis was used to measure the height of the stretching vibration bands of the vinyl group at 1639 cm(-1). A calibration procedure using the considerably higher intensity of the C = O stretching vibration band of the carbonyl ester group at 1725 cm(-1) seemed useful only for high concentrations of methyl methacrylate, i.e. at the beginning of reaction, because this band overlaps that of poly(methyl methacrylate). Use of second-derivative spectra and measuring their values at 1725 cm(-1) enabled estimation of ten times lower concentrations of methyl methacrylate the calibration using the band from the vinyl group.