Ramune Rutkaite

Adsorption of hexavalent chromium on cationic cross-linked starches of different botanic origins.

The influence of origin of native starch used to obtain cationic cross-linked starch (CCS) on the adsorption of Cr(VI) onto CCS has been investigated. CCS granule size is influenced by the botanic source of native starch. The equilibrium adsorption of Cr(VI) onto CCS was described by the Langmuir, Freundlich, Dubinin-Radushkevich and Temkin models. The more equal the adsorption energy of the quaternary ammonium groups in CCS granule as indicated by low value of change of Temkin adsorption energy DeltaE(T) the greater amount of Cr(VI) was adsorbed onto CCS. The value of DeltaE(T) decreased and sorption capacity of CCS increased with the decrease of CCS granule size and with the increase of number of amorphous regions in CCS granules. The affinity of dichromate anions increases and adsorption proceeds more spontaneously when Cr(VI) is adsorbed onto more amorphous CCS. Adsorption process of Cr(VI) onto such CCS is more exothermic and order of system undergoes major changes during adsorption. After the adsorption on CCS Cr(VI) could be regenerated by incineration at temperature of 800 degrees C.

The thermal degradation of copolymers of carbazolylethyl(meth)acrylates and methacrylic acid

The thermal degradation of the (co)polymers of 2-(9-carbazolyl)ethyl methacrylate and 2-(9-carbazolyl)ethyl acrylate with methacrylic acid was studied by thermogravimetry and differential thermal analysis. It was established that the thermal stability of the copolymers is higher than that of the corresponding homopolymers. The degradation of copolymers in which the content of methacrylic acid units is high was found to occur in two stages. One-stage degradation was observed for copolymers in which the amount of methacrylic acid units is lower than 80 mol percent. The formation of intramolecular and intermolecular anhydrides was observed in the thermal degradation of all of the copolymers.

Cationic starch nanoparticles based on polyelectrolyte complexes.

Cationic starch nanoparticles were obtained by aqueous polyelectrolyte complex formation between cationic quaternary ammonium substituted starches and anionic sodium tripolyphosphate. The formation of nanosized starch particles of spherical shape was verified by dynamic light scattering and scanning electron microscopy measurements. The cationic starch nanoparticles of different constitution and containing various contents of free quaternary ammonium groups were produced and their zeta potential was modulated between +4 mV and +34 mV by varying polycation/polyanion ratio. Furthermore, the polyelectrolyte complex formation was confirmed by differential scanning calorimetry and FTIR analyses. The thermal stability of cationic starch nanoparticles increased with the introduction of polysalt into polyelectrolyte complex. The solubilization capacity of nanoparticles was varying with the concentration and composition as revealed by fluorescence probe experiments. The capability to accommodate hydrophobic pyrene quest molecule was decreasing with the increasing number of cationic groups in cationic starches and little depended on polyanion/polycation ratio in starch nanoparticles.

Fluorescence properties of carbazolyl-containing amphiphilic copolymers

Abstract Amphiphilic random copolymers of 2-(9-carbazolyl)-1-methylethyl methacrylate, 2-(9-carbazolyl)ethyl methacrylate or 2-(9-carbazolyl)ethyl acrylate with methacrylic acid were synthesized and their fluorescence properties in aqueous solution were examined. The fluorescence spectra of the copolymers showed monomeric emission. The fluorescence intensity decreased with increase of the content of carbazolyl groups in the copolymers, indicating that some excited-state quenching occurs in these systems. The fluorescence intensity of the copolymers also changed with the change of pH of the solutions. The character of these changes was dependent on the content of carbazole chromophores in the copolymer. Solubilization of 8-anilino-1-naphthalenesulfonic acid ammonium salt and perylene by the copolymers synthesized has been studied. The energy transfer to hydrophobically-bound perylene was facilitated for carbazolylalkylmethacrylate copolymers when compared to that observed for carbazolylalkylacrylate copolymers.

Preparation, stability and antimicrobial activity of cationic cross-linked starch–iodine complexes

Cationic cross-linked starch (CCS)-iodine complexes containing different amounts of quaternary ammonium groups (different degrees of substitution (DS)) and iodine have been obtained by iodine adsorption on CCS from aqueous iodine potassium iodide solution. Equilibrium adsorption studies showed that with an increase of DS the amount of iodine adsorbed on CCS and the affinity of iodine to CCS increased linearly. The influences of the DS of CCS and the amount of adsorbed iodine on the stability of CCS-iodine complexes in a solution of 0.02M sodium acetate and reactivity toward l-tyrosine have been investigated. At the same DS, the stability of CCS-iodine complexes decreased with an increase of the amount of adsorbed iodine. With increasing the DS, the stability of CCS-iodine complexes increased. The iodine consumption in the reaction with l-tyrosine increased significantly with an increase of the amount of adsorbed iodine. The influence of DS on iodine consumption was lower and depended on the amount of adsorbed iodine. The antibacterial activity of CCS-iodine complexes against Bacillus cereus, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli was determined by the broth-dilution and spread-plate methods. The obtained results have demonstrated that an appropriate selection of the CCS-iodine complex composition (the DS of CCS and the amount of adsorbed iodine) could ensure good antimicrobial properties by keeping a low concentration of free iodine in the system. The main advantage of using CCS-iodine complexes as antimicrobial agents is the biodegradability of the polymeric matrix.

Equilibrium adsorption of caffeic, chlorogenic and rosmarinic acids on cationic cross-linked starch with quaternary ammonium groups

In the present study, the equilibrium adsorption of caffeic acid (CA) and its derivatives, namely, chlorogenic (CGA) and rosmarinic (RA) acids on cationic cross-linked starch (CCS) with degree of substitution of quaternary ammonium groups of 0.42 have been investigated in relation to the structure and acidity of phenolic acids. The Langmuir, Freundlich and Dubinin-Radushkevich adsorption models have been used to describe the equilibrium adsorption of CA, CGA and RA from their initial solutions and solutions having the equimolar amount of NaOH at different temperatures. In the case of adsorption from the initial solutions of acids the values of adsorption parameters were closely related to the dissociation constants of investigated acids. According to the increasing effectiveness of adsorption, phenolic acids could be arranged in the following order: CA<CGA<RA, i.e. in the range contrary to increasing value of pKa. At temperature of 30°C the maximum Langmuir sorption capacity was 0.76, 1.11 and 2.68mmol/g for CA, CGA and RA, respectively. The addition of equimolar amounts of NaOH to the acids solutions changed their sorption properties which became mostly related to the acids structure.

Thermal imidization peculiarities of electrospun BPDA-PDA/ODA copolyamic acid nanofibers

AbstractCopolyamic acid (coPAA) based on 4,4′-oxydianiline (ODA), p-phenylenediamine (PDA) and 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) was synthesized in N,N-dimethylformamide (DMF). The preparation of continuous defect-free nanofibers from BPDA-PDA/ODA coPAA was achieved by electrospinning of its DMF solution. The average fiber diameter significantly increased from 385 to 590 nm on increasing the total polymer concentration of the spinning solutions from 5 to 7 wt%. The addition of dodecylethyldimethylammonium bromide (DEDAB) salt to the spinning solution resulted in the procurement of coPAA nanofibers with a much smaller (more than 3 times) average diameter. The coPAA imidization process was investigated through FTIR spectroscopy. The chemical composition and morphology of coPI nanofibers were assessed by X-ray photoelectron spectroscopy and scanning electron microscopy. Imidization under isothermal conditions proceeded faster in the first stage. Activation energies in the first and second imidization stages were similar when DEDAB had been added into the electrospinning solution. Cylindrical or crimped defect-free nanofibers of BPDA-PDA/ODA copolyimide (coPI) were obtained by the stepped thermal imidization of coPAA. The morphology of coPI nanofibers depends on the curing temperature. The crimped coPI nanofibers were most probably due to the relief of residual stress when the curing temperature was higher than the polymer glass transition temperature.

Development of antioxidant food packaging materials containing eugenol for extending display life of fresh beef

In this study, clove essential oil (CL) or eugenol (EU) containing cellulose acetate (CA) or acrylic component/hydrophobically modified starch (AC/S) coatings on corona treated oriented polypropylene film (OPP) were designed and investigated for their possible applications as antioxidant packaging materials for fresh meat. The antioxidant properties of the coatings were investigated by Vapour Phase-DPPH (2,2-diphenyl-1-picrylhydrazyl) assay. The CA coatings containing CL or EU showed 43-92% and 43-94% inhibition against DPPH free radicals through the vapour phase, respectively, whereas AC/S/CL and AC/S/EU coatings resulted in DPPH inhibition of 21-65% and 25-84%, respectively. AC/S/EU and CA/EU coatings on OPP containing from 0.32 ± 0.03 to 6.40 ± 0.14 g/m2 of EU were used to prepare packaging for fresh beef (Longissimus thoracis). After 14 days, the lipid oxidation in beef steaks kept in control and antioxidant packages was 3.33 and 1.00-1.22 mg of malondialdehyde per kilogram of meat, respectively. Moreover, red colour of beef in antioxidant packages was retained.

Biodegradation of cross-linked and cationic starches

The biodegradability and the influence of the degree of substitution of cationic groups or cross-linking level of starch were studied by using enzymatic hydrolysis and two aerobic degradation methods. Cationic starches with a degree of substitution varying from 0 to 0.54 were obtained by modifying native potato starch with 2,3-epoxypropyltrimethylammonium chloride, while cross-linked starches with a degree of cross-linking varying from 0 to 92.5% were obtained by reaction of native potato starch with epichlorohydrin. Enzymatic hydrolysis experiment was performed using α-amylase preparation, and aerobic degradation studies were carried out in liquid and solid media by using ISO 14855-2 and 14851 standards methods. The dextrose equivalent, molecular weight, viscosity and biodegradability parameters were used to assess biodegradation process. Biodegradability of modified starches decreased with increasing degree of modification. The addition of cationic groups to starch to the extent >0.1 mol/molAGU reduced the biodegradability of starch derivatives, and CS became non-biodegradable when DS ≥ 0.54. The cross-linking of starch by building the alkyl chain cross-links between the polysaccharide macromolecules reduced ultimate biodegradability of starch derivatives, when the degree of cross-linking was higher than 92.5%.

Adsorption of rosmarinic acid from aqueous solution on chitosan powder

In present study the adsorption of rosmarinic acid (RA) on chitosan (CH) powder from aqueous solution have been investigated in order to obtain insoluble RA-CH complexes with high amount of RA. The pseudo-second kinetic model and the Langmuir adsorption model described the kinetic and equilibrium adsorption of RA on CH with high correlation coefficients. With the increase of adsorption temperature the rate of adsorption decreased but amount of adsorbed RA increased. It was established that adsorption of RA on CH occurred in two steps, and relevant adsorption mechanism was proposed. The formation of RA-CH with the molar ratio of RA to CH equal to 0.11, 0.22. 0.39, 0.6 and 0.8 was investigated by FT-IR and steady-state fluorescence spectroscopic techniques. By the increase of RA amount in RA-CH complexes the character of both FT-IR and fluorescence spectra changed. The antioxidant activity of RA-CH was investigated by ABTS method and showed that RA-CH having higher amount of adsorbed RA has prolonged antioxidant activity.