Luciana C. Costa

Thermal resistance of magnetic polymeric composites based on styrene, divinylbenzene, and Ni and Co particles

Polymers based on styrene (STY) and divinylbenzene (DVB) are widely used for water treatment. The chemical modification of these materials, with the introduction of chemical groups, increases their selectivity for certain types of contaminants. The incorporation of magnetic particles makes these systems useful for removing contaminants from aquifers, due to their magnetic attraction of certain residues. In this work, STY–DVB resins (unmodified, sulfonated, and impregnated with nickel and cobalt particles) were analyzed by thermogravimetry. The thermal stabilities of all the samples were compared, showing that sulfonation reduces the thermal stability of the resin, but the incorporation of metal particles restores that stability, with the extent of this recovery depending on the type of metal. This result shows that even when the incorporation of metal particles does not involve removal of contaminants by magnetic attraction, this inclusion is still justified because it increases the material’s thermal stability and also makes it more efficient for removing certain types of non-metallic contaminants, as observed in a previous study. Besides this, the thermogravimetric analysis was highly useful to ascertain the changes caused to the materials, including allowing inferences on the semi-quantitative results of the degree of sulfonation and confirming that metal compounds are not only physical mixtures.

Evaluation of bactericidal action of 2-vinylpiridine copolymers containing quaternary ammonium groups and their charge transfer complexes

We report the development of copolymers based on 2-vinylpyridine with different porosity degrees. The copolymers were quaternized with methyl iodide and acrylonitrile to introduce quaternary ammonium groups on pyridine units. To prepare charge transfer complexes, the unmodified copolymers and their derivatives quaternized were impregnated with iodine. The antibacterial properties of all the polymers were evaluated ranging from of the Escherichia coli strain. The unmodified copolymers did not have antibacterial activity against E.Coli suspensions. The quaternization with methyl iodine and acrylonitrile increased the biocidal performance of these copolymers, but only the copolymer with the lowest porosity modified with methyl iodine showed significant bactericidal action for all E. Coli concentrations. The 2-vinylpiridine copolymers quaternized and impregnated with iodine had higher antibacterial activity than the impregnated ones. The charge transfer complexes derived from the copolymer with the lowest porosity and highest swelling capacity in water had the best bactericidal performance.

Preparação de copolímeros à base de 2-vinilpiridina com propriedades bactericidas

We report the development of two copolymers based on 2-vinylpyridine, styrene and divinylbenzene (2Vpy-Sty-DVB) with different porosity degrees. The copolymers were subsequently quaternized with methyl iodide. To prepare charge transfer complexes, the unmodified copolymers and their derivatives quaternized with methyl iodine were impregnated with iodine. The antibacterial properties of the polymers were evaluated in dilutions ranging from 102 to 107 cells/mL of the auxotrophic OHd5-K12 Escherichia coli strain. It was possible to obtain materials with complete antibacterial activity even in the highest cell concentrations tested.

Synergistic Effect of Adsorption and Enzymatic Conversion in the Bisphenol-A Removal by Laccase Immobilized on Poly(glycidyl methacrylate-co-ethyleneglycol dimethacrylate)

Carriers with different functional groups (epoxy, aldehyde, ethyldiazonium, phenyldiazonium and amino) were tested for immobilization of T. versicolor laccase on GMA-co-EGDMA (glycidyl methacrylate-co-ethyleneglycol dimethacrylate) microspheres. Laccase immobilized on GMA-co-EGDMA containing the phenyldiazonium functional group showed the highest activity (96.3 U g). The immobilized laccase was used for removal of bisphenol-A (BPA) from aqueous solution. The temperature effect was significant on activity, but insignificant on BPA removal by the immobilized laccase. In the temperature range 10-60 °C, the removal of BPA by laccase in the immobilized form was about four times higher than that in the free form. Swelling does not affect the activity of immobilized laccase, but after 8 cycles of 2,2’-azino-bis(3-ethylbenzothiazoline6-sulphonic acid) (ABTS) oxidation, non-swollen immobilized laccase was able to retain 71% of the starting activity while the 24 h swollen kept 61%. At neutral pH, adsorption onto the immobilized laccase accounted for 92% of the BPA removed while enzymatic conversion accounted for 8%. However, when increasing the pH to 10, the fraction of BPA removed by adsorption decreased to 67% and by enzymatic conversion increased to 33%.

Resinas poliméricas reticuladas com ação biocida: atual estado da arte

Crosslinked copolymers of divinylbenzene have been extensively employed as supports for catalysts and chelating groups of metal ions, adsorbents of organic compounds and stationary phases for chromatography separations. The use of these copolymers as support for biocidal groups is reported in patents since the 1970s, but only after 2000 were these copolymers also applied as supports for biocidal groups. This paper describes the main combinations of polymeric supports and biocide groups employed in biocide polymer resins. The relationship between the characteristics of these resins and their mechanism of action is also established in this work.