Hydrogels are hydrophilic three-dimensional networks able to hold large amount of water and hydrophilic molecules. Magneto-responsive hydrogels comprise of magnetic nanoparticles dispersed in polymeric networks that can be manipulated under external magnetic field. This review aims at (i) giving a brief overview on the evolution of hydrogels until the design and development of magnetic hydrogels; (ii) describing the types of hydrogels and the basic concepts about superparamagnetic iron oxide nanoparticles, as well as the preparation and characterization of magneto-responsive hydrogels; (iii) displaying the relevant applications of magneto-responsive hydrogels for drug delivery, regenerative medicine of tissues, cancer therapy and environmental issues and (iv) highlighting the challenges and future trends of magneto-responsive hydrogels for 3D and 4D printing.

Alterações morfológicas em superfícies de cobre resultantes da aplicação de um protocolo definido de potencial foram examinadas por microscopia eletrônica de varredura (MEV) e microscopia de força atômica (AFM). Os resultados mostraram uma boa correlação entre o tempo empregado na ativação do eletrodo, microestrutura resultante e a atividade eletroquímica.

Morphologic changes on copper surfaces upon applying an established potential protocol were examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results showed a good correlation between the time employed in the electrode activation and the resulting microstructure and electrochemical activity.

In this study cellulose acetate butyrate (CAB) and carboxymehtylcellulose acetate butyrate (CMCAB) films adsorbed onto silicon wafers were characterized by means of ellipsometry, atomic force microscopy (AFM), sum frequency generation spectroscopy (SFG) and contact angle measurements. The adsorption behavior of lysozyme (LIS) or bovine serum albumin (BSA) onto CAB and CMCAB films was investigated. The amounts of adsorbed LIS or BSA onto CMCAB films were more pronounced than those onto CAB films due to the presence of carboxymethyl group in the CMCAB structure. Besides, the adsorption of BSA molecules on CMCAB films was more favored than that of LIS molecules. Antimicrobial effect of LIS bound to CAB or CMCAB layers was evaluated using Micrococcus luteus as substrate.

Production of ethanol from biomass fermentation has gained much attention recently. Biomass cellulosic material is first converted into glucose either by chemical or by enzymatic process, and then glucose is fermented to ethanol. Considering the current scenario, where many efforts are devoted for the search of green routes to obtaining ethanol from renewable sources, this review presents the relationship between structure and properties of cellulosic material, pre-treatments and hydrolysis of cellulosic material, and structure and function of cellulase enzyme complex.

Eletrodos macroporosos de MnO2 foram preparados por eletrodeposição assistida por molde de partículas esféricas coloidais de poliestireno. A molhabilidade desses filmes foi estudada por medidas de ângulo de contato. Medidas de voltametria cíclica foram realizadas com o objetivo de estudar o seu comportamento como eletrodo para supercapacitores. A capacitância específica obtida foi cerca de 60% maior que a obtida por um eletrodo liso, o que mostra que apesar de a molhabilidade do eletrodo macroporoso ser menor, ocorre alguma penetração do eletrólito pelos poros, aumentando a área eletroativa. Por fim, o eletrodo macroporoso apresentou excelente establidade eletroquímica, não sendo observada queda de capacitância após 1000 ciclos de carga e descarga.

Macroporous MnO2 electrodes prepared by template-assisted electrodeposition using spherical polystyrene colloidal particles are studied. The wettability of such electrodes by a LiClO4 aqueous electrolyte is measured by the contact angle technique. Cyclic voltammetry experiments are performed in order to evaluate the use of these electrodes for electrochemical capacitor applications. The specific capacity obtained is about 60% higher than that obtained for flat MnO2 surfaces showing that, in spite of the wettability being lower, some penetration of the electrolyte into the pores must occur, increasing the electroactive area with respect to the flat electrode. Furthermore, the macroporous electrode showed excellent electrochemical stability, with neither a capacitance decrease nor a loss of morphology, after 1000 cycles.

Resíduos de succinato de isosorbídeo foram incorporados na cadeia principal de poli(L-lactídeo) (PLLA) visando a obtenção de uma nova classe de polímeros biodegradáveis com propriedades melhoradas. Este artigo descreve a síntese e caracterização de quatro tipos de copolímeros de baixa massa molar. O copolímero I foi obtido da mistura dos monômeros L-lactídeo, isosorbídeo e anidrido succínico; II do oligo(L-lactídeo) (PLLA), isosorbídeo e anidrido succínico; III do oligo(succinato de isosorbídeo) (PIS) e L-lactídeo; e IV de reações de transesterificação entre PLLA e PIS. Análises de MALDI-TOFMS e 13C-NMR apresentaram evidências de que cooligomerização foi alcançada em todos os casos. Os dados sugerem que o produto I é um cooligômero aleatório e que os produtos II-IV são cooligômeros em bloco.

Isosorbide succinate moieties were incorporated into poly(L-lactide) (PLLA) backbone in order to obtain a new class of biodegradable polymer with enhanced properties. This paper describes the synthesis and characterization of four types of low molecular weight copolymers. Copolymer I was obtained from monomer mixtures of L-lactide, isosorbide, and succinic anhydride; II from oligo(L-lactide) (PLLA), isosorbide, and succinic anhydride; III from oligo(isosorbide succinate) (PIS) and L-lactide; and IV from transesterification reactions between PLLA and PIS. MALDI-TOFMS and 13C-NMR analyses gave evidence that co-oligomerization was successfully attained in all cases. The data suggested that the product I is a random co-oligomer and the products II-IV are block co-oligomers.

A commercial corrosion inhibitor used in petroleum production was characterized by means of infrared spectroscopy and energy dispersive spectroscopy (EDS). Predicting the adsorption behavior of corrosion inhibitor onto steel, sandstone and esmectite is the key to improve working conditions. In this study, the adsorption kinetics of inhibitor formulations in HCl 15% or in Mud Acid (HCl 13,5% and ammonium bifluoride) onto steel, sandstone and esmectite was determined by means of spectrophotometry. Kinetic parameters indicated that adsorption of inhibitor in the presence of bifluoride was favored. Moreover, the adsorption constant rate was the largest when the substrate was esmectite.

Polysaccharide-based drilling fluids have been often applied in horizontal wells of petroleum reservoirs in Campos, Rio de Janeiro. The present study aimed to understand the mechanism of adsorption and desorption of the drill-in fluid, xanthan, modified starch and lubricant on SiO2 by means of ellipsometry. The effect of pH and brine on the mean thickness (D) of adsorbed layer was systematically investigated. The adsorption was mainly favored under alkaline conditions. A model has been proposed to explain this effect. The adsorption isotherms determined separately for xanthan and starch on SiO2 surfaces could be fitted with the Langmuir model, which yielded similar adsorption constant values.

A imobilização de xiloglucanas (XG) extraídas de sementes de Hymenaea coubaril (HXG) e de Tamarindus indica (TXG) sobre lâminas de Si/SiO2 ou lâminas modificadas com grupos amina a partir de solução aquosa na concentração de 0,5 g L-1 e em pH 3,5 foi investigada através de elipsometria e medidas de microscopia de força atômica (AFM). Os experimentos foram feitos sob condições de equilíbrio (adsorção) ou de não equilíbrio (evaporação do solvente). Sob condições de equilíbrio as cadeias de HXG e TXG não adsorvem sobre lâminas de Si/SiO2, indicando que os grupos SiO- na superfície não interagem com as mesmas. Camadas de TXG e HXG obtidas sobre lâminas de Si/SiO2 por evaporação do solvente apresentaram espessuras de (2,4 ± 0,4) nm e (3,8 ± 0,9) nm, respectivamente. Cadeias de TXG e HXG adsorveram sobre lâminas modificadas com grupos amina formando filmes com (1,0 ± 0,1) nm e (1,3 ± 0,1) nm de espessura, respectivamente. Após evaporação do solvente sobre lâminas modificadas com grupos aminas, formaram-se agregados e fibrilas de TXG e HXG, os quais aumentaram os valores médios de espessura e rugosidade. Independentemente do tipo de substrato, cadeias de HXG tenderam a formar camadas mais espessas que cadeias TXG. Esta tendência foi explicada com base nas características moleculares das cadeias de HXG, como por exemplo, massa molar e tamanho de persistência maiores. As isotermas de adsorção de concanavalina A (Con A) sobre TXG e HXG adsorvidas sobre lâminas modificadas com grupos amina apresentaram valor máximo de (3,3 ± 0,3) mg m-2. Imagens de AFM mostraram moléculas de Con A densamente empacotadas sobre as superfícies de TXG e HXG. Fibrilas e agregados foram observados somente quando as superfícies de TXG e HXG foram preparadas por evaporação do solvente. Nesta situação, as moléculas de Con A adsorveram predominantemente sobre regiões livres de fibrilas e agregados.

Immobilization of xyloglucans extracted from Hymenaea coubaril (HXG) and Tamarindus indica seeds (TXG) on Si/SiO2 wafers or amino-terminated wafers from aqueous solution at concentration of 0.5 g L-1 and pH 3.5 has been investigated by means of ellipsometry and atomic force microscopy (AFM) measurements. Experiments were carried out under equilibrium conditions (adsorption) and non-equilibrium conditions (casting). Under equilibrium conditions neither TXG nor HXG chains adsorbed from solution onto Si/SiO2 surfaces, indicating that negatively charged SiO- groups on the surface do not attract XG chains. Casting TXG and HXG solutions onto Si/SiO2 surfaces led to layers (2.4 ± 0.4) nm and (3.8 ± 0.9) nm thick, respectively. TXG and HXG adsorbed onto amino-terminated surfaces forming layers (1.0 ± 0.1) nm and (1.3 ± 0.1) nm thick, respectively. Upon casting solutions of TXG and HXG onto amino-terminated surfaces, aggregates and fibrils appeared more frequently on the surface, increasing the mean thickness and roughness values. Regardless the substrate, HXG chains tended to form thicker layers than TXG chains did. This trend can be explained with basis on the molecular characteristics of HXG, namely, higher molecular weight and persistence length. The adsorption isotherms of concanavalin A (Con A) onto HXG- and TXG-covered amino-terminated wafers presented maximum adsorbed amount of (3.3 ± 0.3) mg m-2. AFM images shown Con A molecules as small entities densely packed on the surface. The presence of fibrils and aggregates was observed only when the TXG and HXG surfaces were prepared by casting. There ConA molecules adsorbed predominantly on regions free of fibrils and aggregates.

Polietileno de baixa densidade (LLDPE) com comonômeros 1-buteno e 1-octeno foram funcionalizados com anidrido tetrahidroftálico (THA) e anidrido maléico (MA) em solução na presença de peróxido de benzoíla (BPO), de acordo com planejamentos fatoriais. As variáveis testadas foram concentração de anidrido, concentração de peróxido, tempo de reação e tipo de comonômero. As formulações foram analisadas por espectroscopia vibracional no infravermelho FTIR. Na funcionalização com THA o efeito principal tempo de reação foi significativo, assim como, a interação deste com a concentração de THA, enquanto que no caso do MA as concentrações de BPO e MA foram significativas. Poliolefinas modificadas com teores semelhantes de THA e MA foram analisadas por calorimetria exploratória diferencial (DSC) e por difração de raios X (XRD). Amostras modificadas com THA e MA apresentaram redução na temperatura de fusão de 4,3 °C e 1,4 °C, respectivamente, com relação ao polímero original. Alterações devido à funcionalização também foram evidenciadas por forte redução nas áreas dos picos de difração relativos aos planos cristalinos (110) e (200), corroborando com os dados de calorimetria exploratória diferencial (DSC).

Tetrahydrophthalic (THA) and maleic (MA) anhydrides were grafted onto linear low density polyethylene with comonomer 1-butene and 1-octene (LLDPE) in solution in the presence of benzoyl peroxide (BPO) following experimental designs, where anhydride and BPO concentrations, type of comonomer and reaction time were varied. The formulations were analyzed by Fourier transform infrared spectroscopy (FTIR). In the case of THA modified polyolefins, the time of reaction and the interaction between time of reaction and THA concentration influenced the process, whereas the MA and BPO concentrations influenced the grafting of MA onto polyolefins. THA and MA modified polyolefin samples with similar grafting contents were analized by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). THA and MA functionalized polyolefins presented reduction in the melting temperature of 4.3 °C and 1.4 °C, respectively, comparing with the original polymer. These effects corroborate with the strong reduction in the areas of the diffraction peaks (110) and (200) after the grafting process.

In this work the formation of multilayers composed by carboxymethylcellulose (CMC), chitosane and bovine serum albumin (BSA) was studied by ellipsometry. First, the adsorption behavior of carboxymethylcellulose onto amino-terminated surfaces was investigated as a function of molecular weight and average degree of substitution of CMC. The influence of these parameters on the adsorbed amount of CMC onto amino-terminated substrates was absent. However, the interaction of CMC covered surfaces with chitosane and BSA was favored when the average degree of substitution of CMC was increased. The adsorption of BSA onto the polysaccharide systems was studied as a function of pH. At the isoelectric point of BSA a maximum in the adsorbed amount was found.

A adsorção do derivado de celulose, 6-O-(2,3-bis(tiosulfato)propil-oxi-2-hidroxi- propil)-celulose (TSHP), sobre superfícies de prata foi investigada por meio de elipsometria, medidas de ângulo de contato e de espectroscopia de fotoelétrons usando fonte de raios-X (XPS). Os resultados mostraram que a formação de uma densa monocamada de TSHP sobre prata é um processo irreversível, porém lento. A partir dos resultados de XPS foi proposto um modelo para explicar quimissorção de TSHP sobre prata, no qual os grupos tiosulfato sofrem clivagem homolítica, com formação de radicais livres de enxofre. Estes ligam-se covalentemente à superfície de prata, formando uma monocamada estável de TSHP.

The adsorption of a new cellulose derivative,6-O-(2,3-bis(thiosulfato) propyl-oxy-2-hydroxy-propyl)-cellulose (TSHP), onto silver surfaces was investigated by means of ellipsometry, contact angle measurements and X-ray photoelectron spectroscopy (XPS). The results showed that the formation of a dense TSHP monolayer on silver surfaces is an irreversible and slow process. Based on XPS results a model was proposed to explain the chemisorption of TSHP on silver substrates. This model considers the homolytical cleavage of the thiosulfate groups attached to the cellulose chains with the formation of thio radicals, which bind covalently to the silver surface. The formation of silver thiolates lead to a stable TSHP monolayer on silver surfaces.