O relevante papel do agente sililante na modificação de superfícies de polímeros The considerable role of silylant agent in polymer surface modification

<abstract language="eng">The applicability of the silylant agents of the general formula Y3Si-R-X, depends on the reactivity of Y group (halide or alcoxide) attached to silicon and the organic function X (halide, amine, thiol, cyanide, etc) in the extreme position of the chain. Both groups are linked together by an organic chain R, containing usually three methylene groups. A series of these agents can be covalently bonded to an inorganic matrix, since the available OH groups are distributed on the surface, making silica gel the most common support. However, other inorganic oxides, zeolites, lamellar inorganic phosphates and chrysotile can also have these agents anchored. Some illustration are presented for immobilized surface in the use as extractors of cations from dilute aqueous or non-aqueous solutions, catalysts agents, ionic exchanged materials, support for enzyme immobilization, chromatographic applications, use in some industrial features and in many other areas. The evolution of this exciting research field to produce new materials, for many tecnological applications, is strongly dependent on the development of a sensible systematic process for the synthesis of a series of new specific silylant agents

Two Independent Routes To Synthesize Identical Silicas By Grafting Ethylenimine Or 2-aminoethanethiol, Their Cation Adsorbing Abilities, And Thermodynamic Data.

The same grafted silica gel surface was obtained through two distinct procedures: (i) by immobilization of the compound 2-aminoethanethiol on precursor 3-chloropropylsilylsilica gel in a heterogeneous method, and (ii) by reacting ethylenimine with 3-mercaptopropyltrimethoxysilane to give a new silylating agent, which was anchored on the silica gel in a homogenous method. The first anchored surface gave 0.70 mmol g(-1) of molecules covalently bonded per gram of silica. This value contrasts to that obtained with the homogeneous conditions, with 1.74 mmol of pendant groups per gram of silica. Both organofunctionalized surfaces have the ability to adsorb divalent cations from aqueous nitrate solution. The adsorption was performed using a batchwise process and the maximum adsorption capacity followed the sequence Cu>Ni>Co and Ni>Cu>Co for surfaces prepared by the homogeneous and heterogeneous methods, respectively. Through calorimetric titrations, the thermodynamic values of cation-basic center interactions were obtained. Exothermic enthalpy results were obtained for all interactive processes. The calculated free Gibbs energy is in agreement with the spontaneity of the reactions and the positive entropy values for all reactions are favorable for this system.2491-

Influencia da ativaçao acida na estabilidade termica de hibridos vermiculita/epoxido

ALVES, Ana Paula de M. ; GERMANO, A. F. S. ; ARAKAKI, L N H ; Ferreira, U. V. S. ; ARAUJO, A. S. Influencia da ativaçao acida na estabilidade termica de hibridos vermiculita/epoxido. In: CONGRESSO NACIONAL DE ANLISETERMICA E CALORIMETRIA, 7., 2010, São Pedro, SP. Anais... Sao Pedro, SP: ABRATEC, 2010O presente trabalho consiste em explorar a capacidade de reação de vermiculitas ativadas por meio ácido a várias concentrações frente ao agente sililante 3-glicidoxipropiltrimetoxissilano (GPTS) e avaliar a influência da ativação ácida na estabilidade térmica destes novos sólidos. Este interesse está relacionado com a reatividade química do grupo epóxido, localizado na extremidade da molécula orgânica, que possui a habilidade de interagir com centros básicos, possibilitando, a partir de um produto comercial, efetuar a síntese de novos materiais com a incorporação de novas moléculas ao sólido, sendo a estabilidade térmica um ponto chave para outras reaçõe