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THERMAL DEGRADATION OF DOUBLE CROSSLINKED HYDROGEL CHITOSAN MEMBRANES

100%

Pieróg M. , Ostrowska-Czubenko J. , Gierszewska-Drużyńska M.

Progress on Chemistry and Application of Chitin and its Derivatives

2012

tom 17

71 - 78

The thermal degradation behaviour of uncrosslinked and crosslinked chitosan membranes were studied by means of dynamic thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) over the temperature range 25-500ºC in nitrogen atmosphere. Modified chitosan membranes were prepared using a crosslinking method based on covalent crosslinking of chitosan with glutaraldehyde and subsequent ionic crosslinking with sodium citrate, sulfuric acid, sulfosuccinic acid and tripolyphosphate, respectively. Chemical structure of modified chitosan membranes before and after their thermal degradation was characterized by FTIR spectroscopy. Both TGA and DSC experiments as well as spectral results (FTIR spectra of thermal degradation residues) indicated some differences in the mechanism of thermal degradation of uncrosslinked and crosslinked chitosan membranes.

Synthesis and characteristics of chemically modified chitosan membranes with sulfuric acid

86%

Ostrowska-Czubenko J. , Pieróg M.

Polish Journal of Applied Chemistry

2009

tom Vol. 53, nr 2

155-160

Chemically modified chitosan membranes were obtained by treatment of chitosan membranes with sulfuric acid. The effect of chemical modification conditions on molecular and supcrmolecular structure and some physicochemical properties of synthesized membranes were studied using FTIR spectroscopy, X-ray diffraction method, SEM and elemental analysis. FTIR spectra of unmodified and modified chitosan membranes were compared and conclusions concerning the formation of ionic crosslinks between protonated amine groups of chitosan and sulfate anions were drawn out. X-ray analysis indicates that strong interactions between chitosan -NH3~ groups and SO42' ions influence chitosan membrane crystallinity.

Synthesis and characterization of star-shaped poly(ε-caprolactones)s

86%

Łukaszczyk J. , Jelonek P. , Trzebicka B.

Polish Journal of Applied Chemistry

2009

tom Vol. 53, nr 2

147-153

A scries of star-shaped hydroxyl-terminated poly(e-caprolactone)s (SPCLs), with various number of arms and their lengths, was synthesized. SPCLs were synthesized via the ring-opening polymerization of ?-caprolactonc (CL) carried out in the presence of multifunctional alcohol as an initiator and stannous octoate (SnOct2) catalyst. Variation in the number of arm was achieved by using alcohols having 3 (glyccrin), 4 (pcntaerithritol), and 6 (dipcntacrithritol) hydroxyl group. Various arm lengths were obtained by controlling monomer to hydroxyl group molar ratio ([CL]:[OH]). Expected chemical structure of SPCLs was confirmed by NMR and IR spectroscopy. Molar mass of polymers was calculated from 'H NMR and determined by means of SEC-MALLS analysis. Thermal properties of polyesters were investigated using differential scanning calorimetry (DSC).

Competitive inhibitors of free and chitosan-immobilized urease

72%

Zaborska W.

nr 1

The influence of four inhibitors: boric acid, thioglycolic acid, sodium fluoride and acetohydroxamic acid on the activity of urease, both in the native form and immobilized covalently on glutaraldehyde-pretTeated chitosan membrane, was studied. Urea hydrolysis was carried out in phosphate buffer, pH 7, at 25°C at urea concentration of 50 mM. The immobilized urease was more resistant than the native one to the action of all the investigated inhibitors, except boric acid. This property of the enzyme offers a possibility of its practical application.