Sijka Ivanova

Thermoresponsive hydrogels of hydrophobically modified polyglycidol

Abstract Synthesis, swelling properties and thermoresponsive behavior of a new class of hydrogels based on high molar mass polyglycidol are presented. High molar mass polyglycidol was synthesized by coordination polymerization. Thermosensitive poly(glycidol-co-glycidyl ethyl carbamate)s were obtained via a simple chemical modification of the polyglycidol with ethyl isocyanate. Polyglycidol and poly(glycidol-co-glycidyl ethyl carbamate)s were chemically crosslinked in DMF solution using oligomeric poly(ethylene glycol)-bis-(carboxymethyl ether chloride) as crosslinking agent. The hydrogels of degree of swelling of over 1000% were obtained. Thermoresponsive properties of the networks and the swellingdeswelling behavior of hydrogels in response to cyclic changes of the temperature were studied.

Glutaraldehyde-crosslinked poly(glycidol-block-ethylene oxide-block-glycidol) networks with temperatureresponsive swelling behaviour

Abstract In order to obtain temperature-responsive hydrogel networks, poly- (glycidol-block-ethylene oxide-block-glycidol) copolymers were chemically crosslinked by using glutaraldehyde and tetraethoxysilane in a sol-gel reaction. The crystallinity of copolymer networks prepared has been estimated by differential scanning calorimetry. Thermo-responsive properties were evaluated by measuring the equilibrium swelling degree for a series of copolymer hydrogels as a function of temperature.

pH-Sensitive Cationic Copolymers of Different Macromolecular Architecture as Potential Dexamethasone Sodium Phosphate Delivery Systems

This paper describes the synthesis and characterization of cationic copolymers with different macromolecular architecture and drug delivery properties of the corresponding dexamethasone sodium phosphate (DSP)-loaded systems. Copolyelectrolytes comprising poly[2-(acryloyloxy)ethyl] trimethylammonium chloride (PAETMAC) and poly(ethylene glycol) blocks as well as a tri-arm star-shaped PAETMAC were synthesized using cerium(IV) ion-mediated polymerization method. The obtained copolyelectrolytes and corresponding ionic associates with DSP have been characterized by (1)H NMR, Fourier Transform Infrared spectroscopy, and differential scanning calorimetry. The average diameter, size distribution, and ζ-potential of the copolymers and DSP-copolymer ionic associates were determined by dynamic light scattering, and particles were visualized by scanning electron microscopy and transmission electron microscopy. The biocompatibility and cytotoxicity of obtained copolymers were determined. In vitro drug release experiments were carried out to estimate the ability of the obtained nanoparticles for sustained release of DSP for a period of 24 h.

Removal of Cu(II), Co(II) and Fe(III) Ions from Ternary Solution by Free and Entrapped in PVA-Hydrogel Biomass of Penicillium Cyclopium

ABSTRACT Batch sorption equilibrium experiments using free and immobilized Penicillium cyclopium biomass in PVA-hydrogel were carried out using ternary mixture of corresponding metal ion solutions. The metal binding ability of the hybrid hydrogel for Cu(II), Co(II) and Fe(III) ions was determined by atomic absorption spectrophotometer. The performance of free and immobilized biosorbent was evaluated by sorption kinetics and sorption capacities for different metal ions in the mixture. The immobilized system showed higher removal efficiency (expressed as mg metal ions removed per mg metal ions added) in comparison to the free-cell system. In addition, the immobilized system showed two-fold shorter time for reaching the equilibrium in comparison to the free cells. The pseudo-second order kinetic model was applied to the multi-component experimental data and important kinetic parameters of the biosorption process were calculated. The data obtained are in agreement with the assumption that the external mass transfer limitation in the immobilized system can be neglected and biosorption is chemisorption controlled. The immobilized system of organic polymer with entrapped fungal biomass showed high biosorption performance and may be used successfully for the removal of Cu(II), Co(II) and Fe(III) ions from ternary mixed solutions.

Influence of Macromolecular Architecture on the Optical and Humidity-Sensing Properties of Poly(N,N-Dimethylacrylamide)-Based Block Copolymers

The influence of the macromolecular architecture of block copolymers containing poly(N,N-dimethyl acrylamide) (PDMA) on the optical characteristics and sensing properties of corresponding thin films is discussed. Series of hydrophilic PDMA-based copolymers of different chemical composition and chain architecture such as triblock, star-shaped, and branched were synthesized. The copolymers were characterized using conventional spectroscopic techniques as well as methods for characterization of copolymer macromolecular characteristics in solution, namely size-exclusion chromatography and static light scattering. Thin films of the copolymers of nanometer scale thickness were deposited on silicon substrates by the spin-coating method. The refractive index and extinction coefficient of the copolymer films were calculated from the reflectance spectra by using non-linear curve fitting methods and the composition-structure-optical properties relationships were evaluated. Humidity-sensing properties of the films were studied by measuring reflectance spectra of the films at a relative humidity range from 5 to 95%RH. The implementation of the copolymer films as optical sensors of humidity is justified and discussed.