Hydrogels have been extensively explored for biomedical applications due to their ability to absorb high water content in its structure, which gives excellent biocompatibility. This work aims at obtaining biocompatible hydrogels with potential for use in increasing the mechanical strength of bone substitutes, or controlled drug release. Poly (N-vinyl-2-pyrrolidone) hydrogels were prepared by free radical polymerization with and without the addition of acrylic acid. Azobisisobutyronitrile and ammonium persulfate were used as initiator and N,N-methylenebisacrylamide was used as the crosslinking agent. The characterization of the hydrogels was performed by thermogravimetric analysis, differential scanning calorimetry, infrared spectroscopy and swelling properties. The results obtained demonstrate different degrees of crosslinking and swelling of up to 490 ± 30%. The different properties of the hydrogels suggest different applications.

The aim of this paper was to prepare a poly (vinylidene fluoride) (PVDF) membrane using different non-solvents in the coagulation bath for the phase inversion method. In order to increase the mechanical strength of membranes, facing the pressure of work, was used a macro-porous polyester support. The morphology and structure of the resulting membranes were evaluated by scanning electron microscopy, porosity measurements, water and 1-octanol uptake, contact angle, pure water flux, hydraulic permeability and hydraulic resistance. The morphology and pure water flux changed significantly using ethanol (symmetric membrane) and/or water (asymmetric membrane) as the non-solvent. The symmetric membrane presented a high hydrophobic surface (water contact angle ~136°) and a higher pure water flux and porosity than the asymmetric membrane, which presented a lower hydrophobicity surface (water contact angle ~90°). The morphologies obtained suggest different applications.

The membranes properties prepared from water/formic acid (FA)/ polyamide 66 (PA66) and water/hydrochloric acid (HCl)/polyamide 66 (PA 66) systems has been studied. The different solvents interact distinctly with the polymer, affecting the membrane morphology. The asymmetric structure of the membranes showed a dense top layer and a porous sublayer. The membranes M-HCl prepared from HCl/PA 66 system showed a larger dense layer (around 23 μm) in compared to those prepared from FA/PA 66 system (M-FA) (around 10 μm). The membrane morphology was a determinant factor in results of water absorption, porosity and pure water flux. The lower thickness of dense layer in M-FA membranes resulted in a higher water absorption and, consequently, porosity, approximately 50%, compared with M-HCl membranes, approximately 15%. The same trend was observed to permeate flux, the lower thickness of dense layer higher pure water flux.

A B S T R AC TThe membranes prepared from synthetic polymer are used worldwide in separation processes. Polymeric membranes from polyamide 66 (PA 66) in hydrochloric acid (HCl) at the concentrations of 10 and 15 wt.% were prepared by phase inversion method. Poly(vinyl pyrrolidone) (PVP) was used as the polymeric additive in the casting solution to improve the morphology and properties of the PA 66 membranes prepared. The membranes analyzed by Fourier transform infrared (FTIR), maintaining the same chemical structure of pure PA 66 membranes, indicating that the PVP was eliminated in nonsolvent bath. The determination of cloud point showed that PVP addition promotes a thermodynamic instability in the casting solution, reducing the time precipitation and infl uencing in the dense layer formation of the membrane. The scanning electron microscopy (SEM) showed that the PVP addition promoted a decrease in the thickness of dense layer and an increase in the percentage of the porous sublayer, greater uniformity of pores membrane. The pure water fl ux membranes with PVP addition was higher than in membranes of pure PA 66. The pure water fl ux increases from 1365 to 2590 l m -2 h -1 and from 66 to 362 l m -2 h -1 at the concentration of 10 and 15 wt.% of PA 66, respectively.

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Calcium phosphate cements have bioactivity and osteoconductivity and can be molded and replace portions of bone tissue. The aim of this work was to study the obtainment of α-tricalcium phosphate, the main phase of calcium phosphate cement, by wet reaction from calcium nitrate and phosphoric acid. There are no reports about α-tricalcium phosphate obtained by this method. Two routes of chemical precipitation were evaluated and the use of two calcinations temperatures to obtain the phase of cement. The influence of calcination temperature on the mechanical properties of cement was evaluated. Cement samples were characterized by particle size analysis, X-ray diffraction, mechanical strength and scanning electron microscopy. The results demonstrate the strong influence of synthesis route on the crystalline phases of cement and the influence of concentration of reactants on the product of the reaction, as well as, on the mechanical properties of cement.

Resumo: Membranas de polisulfona/poliuretano foram preparadas pelo método de inversão de fases. As membranas preparadas com a adição de fotoiniciador foram irradiadas com lâmpada ultravioleta para aumentar a interação entre os polímeros e o suporte de poliéster utilizado. As membranas com e sem adição de fotoiniciador foram caracterizadas através dos testes de resistência química, capacidade de adsorção de água, determinação de densidade, porosidade, morfologia e fluxo permeado de água. A membrana fotoiniciada apresentou poros com paredes bem definidas e maior estabilidade nos testes de resistência química e fluxo permeado. Ambas as membranas apresentaram valores aproximados na adsorção de água e porosidade. Palavras-chave: Membranas poliméricas, poliuretano, polisulfona, inversão de fase. Preparation and Characterization of Polymeric Membranes from Blended Polysulfone/PolyurethaneAbstract: Polysulfone/polyurethane membranes were prepared by the phase inversion method and irradiated with an ultraviolet light bulb to increase the interaction between polymers and the polyester support. The membranes with and without addition of fotoinitiator were characterized using tests of chemical resistance, water adsorption capacity, density and porosity determination, water permeate flux and membrane morphology. The membrane treated with the fotoinitiator exhibited well defined pores and greater stability in the tests of chemical resistance and water permeate flux. Both membranes had similar values for the water adsorption and porosity. Keywords: Polymeric membranes, poly(urethane), poly(sulfone), inversion phase. IntroduçãoA inversão de fases é um dos processos mais importantes para preparação de membranas poliméricas simétricas e assimétricas [1] . Neste processo, a solução polimérica homogênea é separada em duas fases: uma fase sólida rica em polímero, a qual forma a matriz da membrana e uma fase líquida pobre em polímero a qual forma a estrutura porosa [2,3] . Após a imersão do filme polimérico no banho de coagulação contendo o não-solvente, este irá difundir para a solução polimérica, enquanto o solvente se difundirá no banho. A força motriz para este processo é a diferença de potencial químico existente entre o filme e o banho [4] . A transferência de massa entre o solvente e o não solvente é um fator determinante na morfologia das membranas e para a compreensão dos fenômenos envolvidos na síntese das mesmas [5] . As membranas obtidas por inversão de fases são usadas atualmente em muitas aplicações como a microfiltração, ultrafiltração, osmose inversa e como suporte para membranas compósitas.Alguns dos polímeros mais utilizados na produção de membranas assimétricas, os quais são utilizados neste trabalho são a polisulfona (PSO) e o poliuretano (PU). Membranas de PSO preparadas pelo método de inversão de fase possuem boa resistência mecânica, alta resistência ao calor e elevada estabilidade química sendo amplamente usadas em processos de ultrafiltração e como suporte para membranas compósitas aplicadas em nanofiltraç...

Calcium phosphate cements used as bone substitutes generally have low mechanical strength compared with the bones of the human body. To solve these needs, we have incorporated hydrogels in the manufacture of samples made of alpha-tricalcium phosphate (α-TCP) cement, developing a system of dual-setting cement. This study aimed to produce composite materials by combining α-TCP powder and hydrogels. The composites were prepared using the synthesized powder and four different formulations of hydrogels, using either poly(N-vinyl-2-pyrrolidone) or poly(N-vinyl-2-pyrrolidone-co-acrylic acid), with either azobisisobutyronitrile or ammonium persulfate as initiator. The properties of all composites were evaluated through measuring compressive strength and apparent density and through X-ray diffraction and scanning electron microscopy. The composites showed compressive strengths of around 24 MPa. Soaking the samples in simulated body fluid formed a layer of hydroxyapatite-like crystals on the surface of some samples, showing the bioactivity of the newly developed cements and their potential use as biomaterial.