Evaluation of bio-based monomers from isosorbide used in the formulation of dental composite resins.

The objective of this study was to synthesize two bio-based monomers from isosorbide, the bis(allylcarbonate) isosorbide (IBAC) and the bis(methacrylate) isosorbide (IBM), and to evaluate its effect as Bis-GMA diluents in the formulation of photopolymerizable dental composite resins. The chemical structure of both bio-based monomers was determinate by means H1 NMR, C13 NMR and FTIR spectroscopies. Experimental composites comprising Bis-GMA/IBAC or Bis-GMA/IBM were formulated using 65 %wt of silanized inorganic filler. Experimental materials were compared with a control composite formulated with Bis-GMA/TEGDMA. Double bond conversion, polymerization kinetics, volumetric shrinkage, water sorption, solubility, and flexural properties were investigated. The data were analyzed by one-way ANOVA and Tukey test (α = 0.05). Flexural strength of the experimental materials was similar to the control (p = 0.733). Bis-GMA/IBM achieved the highest values of elastic modulus (p = 0.135). Bis-GMA/IBAC composite achieved the highest values of degree of conversion, while the values of Bis-GMA/IBM composite were similar to the control (p > 0.05). There were no differences in the polymerization shrinkage of the composites, however, the polymerization stress of the experimental materials was lower (p < 0.05). Finally, the cell viability test showed that the experimental resins formulated with the bio-based monomers were not cytotoxic. Due to its characteristics, IBAC and IBM monomers are potentially useful for the formulation of composite materials with applications in dentistry.

Adsorption of textile dyes using an activated carbon and crosslinked polyvinyl phosphonic acid composite.

Activated carbon is one of the most studied materials for the adsorption of textile dyes. The adsorptive properties of this material are a result of its high specific surface area and some of the functional groups acquired during the chemical activation. This work reports the preparation of a composite material using CarZN400 activated carbon and polyelectrolyte poly(VPA-co-TEGDMA). The adsorptive properties of the material obtained are a result of the combination of the high specific surface area of the carbon and the ionic exchange capability of the polyelectrolyte. The covering of the surface of activated carbon with poly(VPA-co-TEGDMA) allowed to obtain a composite material (CarZN400C) with greater adsorption capacity for cationic dyes compared to the carbon. The adsorption isotherms of the dyes fit Langmuir's model, and the adsorptive capacities for cationic dyes for CarZN400C ranged between 222 and 416 mg/g. The kinetic study showed that the adsorption of basic and acid dyes fit the pseudo-second order kinetic model. CarZN400C also exhibited the ability to adsorb textile dyes present in wastewater. It was observed that, when making a previous treatment of the wastewater using coagulation-flocculation followed by adsorption using CarZN400C, it was possible to obtain removal percentages of color close to 100%. The wastewaters treated by coagulation-flocculation and adsorption improved their quality by decreasing the value for COD.

Elimination of textile dyes using activated carbons prepared from vegetable residues and their characterization.

In this study, three mesoporous activated carbons prepared from vegetable residues were used to remove acid, basic, and direct dyes from aqueous solutions, and reactive and vat dyes from textile wastewater. Granular carbons obtained by chemical activation at 673 K with phosphoric acid from prickly pear peels (CarTunaQ), broccoli stems (CarBrocQ), and white sapote seeds (CarZapQ) were highly efficient for the removal of dyes. Adsorption equilibrium studies were carried out in batch systems and treated with Langmuir and Freundlich isotherms. The maximum adsorption capacities calculated from the Langmuir isotherms ranged between 131.6 and 312.5 mg/g for acid dyes, and between 277.8 and 500.0 mg/g for basic dyes at 303 K. Our objective in this paper was to show that vegetable wastes can serve as precursors for activated carbons that can be used for the adsorption of dyes. Specifically CarBrocQ was the best carbon produced for the removal of textile dyes. The color removal of dyes present in textile wastewaters was compared with that of a commercial powdered carbon, and it was found that the carbons produced using waste material reached similar efficiency levels. Carbon samples were characterized by bulk density, point of zero charge, thermogravimetric analysis, elemental analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, methylene blue adsorption isotherms at 303 K, and nitrogen adsorption isotherms at 77 K (SBET). The results show that the activated carbons possess a large specific surface area (1025-1177 m(2)/g) and high total pore volume (1.06-2.16 cm(3)/g) with average pore size diameters between 4.1 and 8.4 nm. Desorption and regeneration tests were made to test the viability of reusing the activated carbons.

Diallyl 5-[(4-hexyl-oxyphen-yl)imino-meth-yl]-m-phenyl-ene dicarbonate.

The title mol-ecule, C(27)H(31)NO(7), an imine derivative bearing both carbonate and allyl functionalities, was synthesized in the hope of obtaining a mesogenic polymerizable material. The allyl-carbonate arms are fully disordered over two sets of sites, reflecting a large degree of rotational freedom about σ bonds [occupancies: 0.665 (9)/0.335 (9) for one substituent, 0.564 (9)/0.436 (9) for the other]. In contrast, the hexyl chain is ordered, and presents the common all-trans extended conformation. The benzene rings connected via the imine group make a dihedral angle of 9.64 (11)°. In the crystal, the Y-shaped mol-ecules are weakly associated into centrosymmetric dimers through pairs of C-H⋯O(hex-yl) contacts. The resulting layers of dimers, approximately parallel to (25), are closely packed in the crystal, allowing π⋯π inter-actions between benzene rings of neighboring layers: the separation between the centroid of the benzene ring substituted by allyl-carbonate and the centroid of the benzene ring bearing the hex-yloxy group in the adjacent layer is 3.895 (1) Å.