Preparation and Characterization of Strongly Sulfonated Acid Block and Random Copolymer Membranes for Acetic Acid Esterification with 2-Propanol.

In this paper, we report the synthesis of block and random copolymers of 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS) and methyl methacrylate (MMA), with different AMPS feed ratios. These solution-processable copolymers with strongly sulfonated acid groups resulted in membranes with tunable ion exchange (IEC) and water absorption capacities. AFM images confirmed the microphase separation of PAMPS-b-PMMA-1:1 block copolymer membrane, annealed under the appropriate conditions. The resulting copolymers from the random combination of a 1:1 molar ratio of AMPS and MMA monomers are effective at enhancing the esterification conversion of acetic acid, when compared with a reaction catalyzed by PAMPS-b-PMMA block copolymers and the previously studied catalytic membranes. With the PAMPS-co-PMMA-1:1 membrane, the esterification reaction using acetic acid achieved 85% isopropyl acetate. These results are closely correlated with the increase in IEC (2.63 mmol H+g-1) and the relationship between weight loss (20.3%) and swelling degree (68%) in 2-propanol.

Silanized graphene oxide as a reinforcing agent for acrylic bone cements: physicochemical, mechanical and biological characterization.

Recently, different carbon-based nanomaterials have been used as reinforcing agents in acrylic bone cement formulations. Among them, graphene oxide (GO) has attracted the attention of scientific community since it could improve not only the mechanical properties but also the biocompatibility characteristics of these materials. However, using GO presents some drawbacks, such as its poor dispersion and lack of interaction with polymeric matrices, which should be prior resolved to achieve its optimal performance in acrylic bone cement. Thus, in this work, GO was treated with 3-methacryloxy propyl trimethoxy silane at various concentrations (1, 3 and 5 wt.%) to improve the interaction between the nanofiller and the poly (methyl methacrylate) matrix. Modified GO was incorporated at different percentages (0.1, 0.5 and 0.75 wt.%) into acrylic bone cement formulations and some properties were evaluated. The silanization process of the GO was confirmed by FTIR, TGA and EDX. The improvement in the mechanical performance was monitored on the compression properties whereas those related with biological properties were evaluated by osteoblast cell viability and hemocompatibility tests. Results suggest that using a 1 wt.% of the silane coupling agent, during surface treatment of GO, yields the best mechanical performance in this type of materials. It was also found that the presence of neat GO or silanized GO does not compromise the cytocompatibility and hemocompatibility of acrylic bone cement formulations.

Towards optimization of the silanization process of hydroxyapatite for its use in bone cement formulations.

The aim of this work was to provide some fundamental information for optimization of silanization of hydroxyapatite intended for bone cement formulations. The effect of 3-(trimethoxysilyl) propyl methacrylate (MPS) concentration and solvent system (acetone/water or methanol/water mixtures) during HA silanization was monitored by X-ray diffraction (XRD), FTIR spectroscopy and EDX analysis. The effect of silanized HA on the mechanical properties of acrylic bone cements is also reported. It was found that the silanization process rendered hydroxyapatite with lower crystallinity compared to untreated HA. Through EDX, it was observed that the silicon concentration in the HA particles was higher for acetone-water than that obtained for methanol-water system, although the mechanical performance of cements prepared with these particles exhibited the opposite behavior. Taking all these results together, it is concluded that methanol-water system containing MPS at 3wt.% provides the better results during silanization process of HA.