Valorização de fibras de sisal: síntese de ésteres de celulose e preparação de materiais

Rodrigues, Bruno V. M.

doi:10.11606/t.75.2014.tde-06052015-143056

Cited by 2 publications

(3 citation statements)

References 70 publications

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“…Increasing the number of fiber connections promotes augmentation of the bulk density and also of the tensile strength within certain limits. 29,30 The considerable increase in the Young's modulus (from 6.5 ± 0.1 to 15 ± 2 MPa, observed as the content of PDMAEMA on raises from 20% to 50% w/w) illustrates this effect (see also SEM images, Figure 1). Thus, it is possible that in PCL/ PDMAEMA 80/20 (w/w) the resultant average fiber diameter is not small enough to hold together adjacent fibers under mechanical stress.…”

Section: Acs Applied Materials and Interfacesmentioning

confidence: 91%

Antibacterial Performance of a PCL–PDMAEMA Blend Nanofiber-Based Scaffold Enhanced with Immobilized Silver Nanoparticles

Santos¹,

Bonkovoski²,

Garcia³

et al. 2017

ACS Appl. Mater. Interfaces

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In the present study, nanofiber meshes (NFs), composed of polycaprolactone and poly[(2-dimethylamino)ethyl methacrylate] at 80/20 and 50/50 PCL/PDMAEMA blend ratios, were obtained through electrospinning. Silver nanoparticles (AgNPs) formed in situ were then immobilized on NF surfaces through adsorption processes at different pHs. It was possible to observe that the amount of NF-AgNPs can be tuned by changing the pH of AgNPs immobilization and the PCL/PDMAEMA ratio in the blend. The neat NF and NF-AgNPs were characterized with respect to their morphology and mechanical properties. The effects of AgNPs on the antibacterial activities and cytotoxicity of meshes were also evaluated. The antibacterial performance of such NF was improved by the presence of AgNPs. The NF-AgNPs presented good antibacterial effect against S. aureus and partial toxicity against E. coli and P. aeruginosa. Also, compared with neat PCL/PDMAEMA the NF-AgNPs presented lower cytotoxicity against VERO cells, showing their potential for applications in tissue engineering for different types of cell growth.

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Section: Acs Applied Materials and Interfacesmentioning

confidence: 91%

Antibacterial Performance of a PCL–PDMAEMA Blend Nanofiber-Based Scaffold Enhanced with Immobilized Silver Nanoparticles

Santos¹,

Bonkovoski²,

Garcia³

et al. 2017

ACS Appl. Mater. Interfaces

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“…As razões molares selecionadas foram 3, 6 e 12 visando obter ésteres de celulose com 1, 2 e 3 graus médios de substituição. Deve-se salientar a possibilidade de ocorrer agregação das cadeias de celulose em solução, o que dificulta a utilização de reagentes em condições estequiométricas e a completa homogeneidade e uniformidade da distribuição dos substituintes ao longo da cadeia (RAMOS, 2005;RODRIGUES, 2014).…”

Section: Dissolução Em Sistema Licl/dmacunclassified

“…Os valores de ângulo de contato têm sido frequentemente utilizados para caracterizar propriedades de superfície, tais como caráter hidrofílico, rugosidade e heterogeneidade (GOMES et al, 2007;RODRIGUES, 2014 (BARTHLOTT et al, 2005).…”

Section: âNgulo De Contatounclassified

Ésteres de celulose: síntese, propriedades e preparação de mantas e esferas visando aplicações em imobilização de lipase

Polez¹

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The aim of the present study was the esterification of cotton linter cellulose in homogeneous medium, using as solvent system lithium chloride/N,N-dimethylacetamide (LiCl/DMAc), and hexanoic anhydride or benzoyl chloride as esterifying agents. Cotton linter cellulose was used because it is a fast-growing source and is considered the highest purity cellulose isolated from plant sources. The synthesis of cellulose esters (hexanoate, benzoate as well as mixed esters, cellulose hexanoate-benzoate) aimed to obtain different average degrees of substitution (DS = 1, 2 and 3) by adjusting the Molesterifying agent/ MolOH of AGU ratio. The obtained cellulose esters (characterized by FTIR, 1 H NMR, and TGA) were used as starting materials in the preparation of mats and spheres, which corresponded to a second goal of the study. Cellulose hexanoate mats were obtained by electrospinning technique from tetrahydrofuran/N,N-dimethylacetamide (THF/DMAc) solutions, and cellulose benzoate and hexanoate benzoate mats were prepared from trifluoroacetic acid (TFA) solutions. Electrospinning resulted in ultrathin fiber networks (> 100 nm) over a wide diameter range by varying the experimental conditions such as polymeric solution flow rate (5.5, 15.5 and 45.5 μL.min-1), distance (5, 10, 15 and 25 cm), applied voltage between needle and collector (10, 15, 20 and 25 kV) and polymeric solution concentration (7, 9, 11, 13 and 15%). When evaluating SEM micrographs, it was observed that a smaller injection flow favored the formation of ultrathin fibers up to 150 nm. The spheres were prepared by dripping a solution of cellulose ester and acetone in non-solvent (water or methanol). The spheres obtained in water had slightly larger diameters and less rough surface when compared to spheres obtained in methanol. Mats and spheres of cellulose esters, selected from the results of the respective characterizations, were used as supports for immobilization of Pseudomonas fluorescens lipases (PFL) by encapsulation and subsequently applied to the enzymatic kinetic resolution of racemic hydrochlorins by reaction with vinyl acetate catalyzed by immobilized lipase, this step is the third goal of this study. The kinetic resolution was analyzed by Gas Chromatography coupled to a flame ionization detector (GC-FID) to determine the reaction parameters. The nonimmobilized reference lipase showed moderate conversion (c = 34%), excellent enantiomeric purity (eep = 98%) and excellent enantiomeric ratio (E = 212). Lipase immobilized in mats did not show catalytic activity, probably due to the voltage applied during electroporation, which may have inactivated the enzymes, and/or the application of the blankets on support, which may have impaired enzyme access. For Hex 12 beads (15% LPF) obtained using water as a counter solvent, the results were promising, superior conversion after 120h reaction (c = 40%) and 94% enantiomeric purity. By reusing the spheres in a second cycle, a 24% reduction in the reaction conversion rate was observed.

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Valorização de fibras de sisal: síntese de ésteres de celulose e preparação de materiais

Cited by 2 publications

References 70 publications

Antibacterial Performance of a PCL–PDMAEMA Blend Nanofiber-Based Scaffold Enhanced with Immobilized Silver Nanoparticles

Antibacterial Performance of a PCL–PDMAEMA Blend Nanofiber-Based Scaffold Enhanced with Immobilized Silver Nanoparticles

Ésteres de celulose: síntese, propriedades e preparação de mantas e esferas visando aplicações em imobilização de lipase

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