Stability and interface properties of thin cellulose ester films adsorbed from acetone and ethyl acetate solutions

Stability and interface properties of cellulose acetate propionate (CAP) and cellulose acetate butyrate (CAB) films adsorbed from acetone or ethyl acetate onto Si wafers have been investigated by means of contact angle measurements and atomic force microscopy (AFM). Surface energy (gamma(total)(S)) values determined for CAP adsorbed from acetone are larger than those from ethyl acetate. In the case of CAB films adsorbed from ethyl acetate and acetone were similar. Dewetting was observed by AFM only for CAP films prepared from ethyl acetate. Positive values of effective Hamaker constant (A(eff)) were found only for CAP prepared from ethyl acetate, corroborating with dewetting phenomena observed by AFM. Oil the contrary, negative values of A(eff) were determined for CAP and CAB prepared from acetone and for CAB prepared from ethyl acetate, Corroborating with experimental observations. Sum frequency generation (SFG) vibrational spectra indicated that CAP and CAB films prepared from ethyl acetate present more alkyl groups oriented perpendicularly to the polymer-air interface than those films prepared from acetone. Such preferential orientation corroborates with macroscopic contact angle measurements. Moreover, SFG spectra showed that acetone hinds strongly to Si wafers, creating a new surface for CAP and CAB films. (C) 2008 Elsevier Inc. All rights reserved.

Characteristics of thin cellulose ester films spin-coated from acetone and ethyl acetate solutions

Spin-coated films of cellulose acetate (CA), cellulose acetate propionate (CAP), cellulose acetate butyrate (CAB) and carboxymethylcellulose acetate butyrate (CMCAB) have been characterized by ellipsometry, atomic force microscopy (AFM) and contact angle measurements. The films were spin-coated onto silicon wafers, a polar surface. Mean thickness values were determined by means of ellipsometry and AFM as a function of polymer concentration in solutions prepared either in acetone or in ethyl acetate (EA), both are good solvents for the cellulose esters. The results were discussed in the light of solvent evaporation rate and interaction energy between substrate and solvent. The effects of annealing and type of cellulose ester on film thickness, film morphology, surface roughness and surface wettability were also investigated.

Application of 1-Allyl-3-(1-butyl)imidazolium Chloride in the Synthesis of Cellulose Esters: Properties of the Ionic Liquid, and Comparison with Other Solvents

The ionic liquid (IL), 1-allyl-3-(1-butyl)imidazolium chloride (AlBuImCl), has been synthesized and its properties determined. Increase in the temperature increased its conductivity and decreased its density, polarity, and viscosity. Microcrystalline cellulose (MCC), dissolves in thisIL by heating at 80 degrees C; this did not affect its degree of polymerization, decreased its index of crystallinity (Ic), and changed in morphology after regeneration. Convenient acylation of MCC was achieved by using 50% excess anhydride at 80 degrees C, for 24 or 48 h for acetic and butyric anhydride, respectively. The composition of the mixed esters depended on the initial ratio of the anhydrides, and their order of addition.

Acetylation of cellulose in LiCl-N,N-dimethylacetamide: first report on the correlation between the reaction efficiency and the aggregation number of dissolved cellulose

The acylation of three cellulose samples by acetic anhydride, Ac(2)O, in the solvent system LiCl/N,N-dimethylacetamide, DMAc (4 h, 110 A degrees C), has been revisited in order to investigate the dependence of the reaction efficiency on the structural characteristics of cellulose, and its aggregation in solution. The cellulose samples employed included microcrystalline, MCC; mercerized cotton linters, M-cotton, and mercerized sisal, M-sisal. The reaction efficiency expresses the relationship between the degree of substitution, DS, of the ester obtained, and the molar ratio Ac(2)O/AGU (anhydroglucose unit of the biopolymer); 100% efficiency means obtaining DS = 3 at Ac(2)O/AGU = 3. For all celluloses, the dependence of DS on Ac(2)O/AGU is described by an exponential decay equation: DS = DS(o) - Ae(-[(Ac2O/AGU)/B]); (A) and (B) are regression coefficients, and DS(o) is the calculated maximum degree of substitution, achieved under the conditions of each experiment. Values of (B) are clearly dependent on the cellulose employed: B((M-cotton)) > B((M-sisal)) > B((MCC)); they correlate qualitatively with the degree of polymerization of cellulose, and linearly with the aggregation number, N(agg), of the dissolved biopolymer, as calculated from static light scattering measurements: (B) = 1.709 + 0.034 N(agg). To our knowledge, this is the first report on the latter correlation; it shows the importance of the physical state of dissolved cellulose, and serves to explain, in part, the need to use distinct reaction conditions for MCC and fibrous celluloses, in particular Ac(2)O/AGU, time, temperature.

Urea amperometric biosensors based on a multifunctional bipolymeric layer: Comparing enzyme immobilization methods

This paper outlines the results obtained with biosensors designed for urea amperometric detection. The incorporation of urease into a bipolymeric substrate consisting of poly(pyrrole) and poly(5-amino-1-naphthol) was performed through four different approaches: direct adsorption, entrapment in cellulose acetate layer. cross-linking with glutaraldehyde, and also covalent attachment to the polymeric matrix. Poly(pyrrole) acts as amperometric transducer in these biosensors, while poly(5-amino-1-naphthol) drastically reduces the interference signal of agents such as ascorbic and uric acids. The biosensors containing urease covalently attached to the substrate provided interesting results in terms of sensitivity towards urea (0.50 mu A cm(-2) mmol(-1) L), lifetime (20 days) and short response times, due to the enzyme immobilization method used. All biosensors analyzed showed also a wide linear concentration range (up to 100 mmol L(-1)) and low detection limits (0.22-0.58 mmol L(-1)). (C) 2009 Elsevier B.V. All rights reserved.

Solution behavior and surface properties of carboxymethylcellulose acetate butyrate

Solution behavior of carboxymethylcellulose acetate butyrate (CMCAB) in acetone and ethyl acetate has been investigated by small-angle X-ray scattering (SAXS) and capillary viscometry and correlated with the characteristics of CMCAB films. Viscosity and SAXS measurements showed that ethyl acetate is a better solvent than acetone for CMCAB. Thin films of CMCAB were deposited onto silicon wafers (Si/SiO(2)) by spin coating. AFM images revealed that CMCAB spin coated films from solutions prepared in ethyl acetate were homogeneous and flat. However, films obtained from solutions in acetone were very rough. Contact angle measurements with polar and apolar test liquids characterized CMCAB surfaces as hydrophobic and allowed estimating the surface energy of CMCAB. Sum frequency generation vibrational spectroscopy was used to understand the role played by solvents and to gain insight about molecular orientation at Si/SiO(2)/CMCAB interface.

Probing the dependence of the properties of cellulose acetates and their films on the degree of biopolymer substitution: use of solvatochromic indicators and thermal analysis

Although cellulose acetates, CAs, are extensively employed there is scant information about the systematic dependence of their properties on their degree of substitution, DS; this is the subject of the present work. Nine CAs samples, DS from 0.83 to 3.0 were synthesized; their films were prepared. The following solvatochromic probes have been employed in order to determine the empirical polarity, E (T)(33); ""acidity, alpha""; ""basicity, beta"", and ""dipolarity/polarizability, pi*"" of the casted films: 2,6-dichloro-4-(2,4,6-triphenyl-pyridinium-1-yl) phenolate, WB; 4-nitroaniline; 4-nitroanisole; 4-nitro-N,N-dimethylaniline; 2,6-diphenyl-4-(2,4,6-triphenyl-pyridinium-1-yl)phenolate, RB. Additionally, two systems, ethanol plus ethyl acetate (EtOH-EtAc), and cellulose plus cellulose triacetate, CTA, were employed as models for CAs of different DS. Regarding the model systems, the following was observed: (i) For EtOH-EtAc, the dependence of all solvatochromic parameters on the ""equivalent-DS"" of the binary mixture was non-linear because of preferential solvation; (ii) The dependence of E (T)(33) on equivalent DS of the cellulose-CTA films is linear, but the slope is smaller than that of the corresponding plot for CAs. This is attributed to the more efficient hydrogen bonding in the model system, a conclusion corroborated by IR measurements. The dependence of solvatochromic parameters of CAs on their DS is described by the simple equations; a consequence of the substitution of the OH by the ester group. The thermal properties of bulk CAs samples were investigated by DSC and TGA; their dependence on DS is described by simple equations. The relevance of these data to the processing and applications of CAs is briefly discussed.

PHYSICAL AND CHEMICAL CHARACTERISTICS OF FROZEN GROUND BEEF AND AGED BEEF MEAT FROM BOS INDICUS STEERS SUPPLEMENTED WITH alpha-TOCOPHEROL ACETATE

The objective of this study was to evaluate the effects of diet supplementation with vitamin E on the physical and chemical characteristics of ground, frozen and stored or aged Quadriceps femoris (QF) and Longissimus dorsi (LD) muscles from Nellore steers fed high concentrate diets. Muscles were obtained from 24 animals that were 30 months old with a mean live weight of 279 kg. Half of the animals received daily doses of 1,000 mg of alpha-tocopherol acetate (VIT E) per head per day that was added to 100 g of corn meal. The other half received 100 g of corn meal without the antioxidant. Twenty-four hours after slaughtering, QF samples from each animal were ground, frozen and stored for up to 6 months. In addition, 4 samples from the LD of each animal were vacuum packed individually and kept for 21 days. All samples were analyzed to determine the pH, color and water-holding-capacity. The VIT E supplementation improved only the water loss characteristics of frozen ground QF and did not have any positive effect on the physical-chemical characteristics of the aged LD.

Lifetime Overproduction of Circulating Angiotensin-(1-7) Attenuates Deoxycorticosterone Acetate-Salt Hypertension-Induced Cardiac Dysfunction and Remodeling

We evaluated the development of arterial hypertension, cardiac function, and collagen deposition, as well as the level of components of the renin-angiotensin system in the heart of transgenic rats that overexpress an angiotensin (Ang)-(1-7)-producing fusion protein, TGR(A1-7)3292 (TG), which induces a lifetime increase in circulating levels of this peptide. After 30 days of the induction of the deoxycorticosterone acetate (DOCA)-salt hypertension model, DOCA-TG rats were hypertensive but presented a lower systolic arterial pressure in comparison with DOCA-Sprague-Dawley (SD) rats. In contrast to DOCA-SD rats that presented left ventricle (LV) hypertrophy and diastolic dysfunction, DOCA-TG rats did not develop cardiac hypertrophy or changes in ventricular function. In addition, DOCA-TG rats showed attenuation in mRNA expression for collagen type I and III compared with the increased levels of DOCA-SD rats. Ang II plasma and LV levels were reduced in SD and TG hypertensive rats in comparison with normotensive animals. DOCA-TG rats presented a reduction in plasma Ang-(1-7) levels; however, there was a great increase in Ang-(1-7) (approximate to 3-fold) accompanied by a decrease in mRNA expression of both angiotensin-converting enzyme and angiotensin-converting enzyme 2 in the LV. The mRNA expression of Mas and Ang II type 1 receptors in the LV was not significantly changed in DOCA-SD or DOCA-TG rats. This study showed that TG rats with increased circulating levels of Ang-(1-7) are protected against cardiac dysfunction and fibrosis and also present an attenuated increase in blood pressure after DOCA-salt hypertension. In addition, DOCA-TG rats showed an important local increase in Ang-(1-7) levels in the LV, which might have contributed to the attenuation of cardiac dysfunction and prefibrotic lesions. (Hypertension. 2010;55:889-896.)

Extracellular Signal-Regulated Kinase 1/2 Activation, via Downregulation of Mitogen-Activated Protein Kinase Phosphatase 1, Mediates Sex Differences in Desoxycorticosterone Acetate-Salt Hypertension Vascular Reactivity

Extracellular signal-regulated kinase (ERK) 1/2 has been reported to play a role in vascular dysfunction associated with mineralocorticoid hypertension. We hypothesized that, compared with female rats, an upregulation of ERK1/2 signaling in the vasculature of male rats contributes to augmented contractile responses in mineralocorticoid hypertension. Uninephrectomized male and female Sprague-Dawley rats received desoxycorticosterone acetate (DOCA) pellets (200 mg per animal) and saline to drink for 3 weeks. Control uninephrectomized rats received tap water to drink. Blood pressure, measured by telemetry, was significantly higher in male DOCA rats (191 +/- 3 mm Hg) compared with female DOCA rats (172 +/- 7 mm Hg; n=5). DOCA treatment resulted in augmented contractile responses to phenylephrine in aorta (22 +/- 3 mN; n=6) and small mesenteric arteries (13 +/- 2 mN; n=6) from male DOCA rats versus uninephrectomized male rats (16 +/- 3 and 10 +/- 2 mN, respectively; P<0.05) and female DOCA rats (15 +/- 1 and 11 +/- 1 mN, respectively). ERK1/2 inhibition with PD-98059 (10 mu mol/L) abrogated increased contraction to phenylephrine in aorta (14 +/- 2 mN) and small mesenteric arteries (10 +/- 2 mN) from male DOCA rats, without any effects in arteries from male uninephrectomized or female animals. Compared with the other groups, phosphorylated ERK1/2 levels were increased in the aorta from male DOCA rats, whereas mitogen-activated protein kinase phosphatase 1 expression was decreased. Interleukin-10 plasma levels, which positively regulate mitogen-activated protein kinase phosphatase 1 activity, were reduced in male DOCA-salt rats. We speculate that augmented vascular reactivity in male hypertensive rats is mediated via activation of the ERK1/2 pathway. In addition, mitogen-activated protein kinase phosphatase 1 and interleukin 10 play regulatory roles in this process. (Hypertension. 2010; 55: 172-179.)

Impaired Vasodilator Activity in Deoxycorticosterone Acetate-Salt Hypertension Is Associated With Increased Protein O-GlcNAcylation

Hyperglycemia, which increases O-linked beta-N-acetylglucosamine (O-GlcNAc) proteins, leads to changes in vascular reactivity. Because vascular dysfunction is a key feature of arterial hypertension, we hypothesized that vessels from deoxycorticosterone acetate and salt (DOCA-salt) rats exhibit increased O-GlcNAc proteins, which is associated with increased reactivity to constrictor stimuli. Aortas from DOCA rats exhibited increased contraction to phenylephrine (E(max) [mN] = 17.6 +/- 4 versus 10.7 +/- 2 control; n = 6) and decreased relaxation to acetylcholine (47.6 +/- 6% versus 73.2 +/- 10% control; n = 8) versus arteries from uninephrectomized rats. O- GlcNAc protein content was increased in aortas from DOCA rats (arbitrary units = 3.8 +/- 0.3 versus 2.3 +/- 0.3 control; n = 5). PugNAc (O- GlcNAcase inhibitor; 100 mu mol/L; 24 hours) increased vascular O- GlcNAc proteins, augmented phenylephrine vascular reactivity (18.2 +/- 2 versus 10.7 +/- 3 vehicle; n = 6), and decreased acetylcholine dilation in uninephrectomized (41.4 +/- 6 versus 73.2 +/- 3 vehicle; n = 6) but not in DOCA rats (phenylephrine, 16.5 +/- 3 versus 18.6 +/- 3 vehicle, n = 6; acetylcholine, 44.7 +/- 8 versus 47.6 +/- 7 vehicle, n = 6). PugNAc did not change total vascular endothelial nitric oxide synthase levels, but reduced endothelial nitric oxide synthase(Ser-1177) and Akt(Ser-473) phosphorylation (P < 0.05). Aortas from DOCA rats also exhibited decreased levels of endothelial nitric oxide synthase(Ser-1177) and Akt(Ser-473) (P < 0.05) but no changes in total endothelial nitric oxide synthase or Akt. Vascular O-GlcNAc-modified endothelial nitric oxide synthase was increased in DOCA rats. Blood glucose was similar in DOCA and uninephrectomized rats. Expression of O- GlcNAc transferase, glutamine: fructose-6-phosphate amidotransferase, and O- GlcNAcase, enzymes that directly modulate O-GlcNAcylation, was decreased in arteries from DOCA rats (P < 0.05). This is the first study showing that O-GlcNAcylation modulates vascular reactivity in normoglycemic conditions and that vascular O- GlcNAc proteins are increased in DOCA-salt hypertension. Modulation of increased vascular O-GlcNAcylation may represent a novel therapeutic approach in mineralocorticoid hypertension. (Hypertension. 2009; 53: 166-174.)

A Morphological View of the Sodium 4,4 `-Distyrylbiphenyl Sulfonate Fluorescent Brightness Distribution on Regenerated Cellulose Fibers

Evidence of the sorption of the whitening agent sodium 4,4`-distyrylbiphenyl sulfonate in the presence of the anionic surfactant sodium dodecylsulfate or the cationic surfactant dodecyl trimethyl ammonium chloride on regenerated cellulose fibers is given by several microscopy techniques. Scanning electron microscopy provided images of the cylindrical fibers with dimensions of 3.5 cm (length) and 13.3 mu m (thickness), with empty cores of 1 mu m diameter and a smooth surface. Atomic force microscopy showed a fiber surface with disoriented nanometric domains using both tapping-mode height and phase image modes. Atomic force microscopy also showed that the whitening agent and surfactant molecules were sorbed onto the fiber surface, in agreement with the adsolubilization sorption model. Transmission electron microscopy showed fibers with nanometric parallel cylinders, surrounded by holes where the fluorescent whitening molecules accumulated. On the basis of these techniques, we conclude that the sorption process occurs preferentially on the fiber surface in contact with the water solution, and under saturated conditions, the whitening agent penetrates into the pores and are simultaneously sorbed on the pore walls bulk, forming molecular aggregates. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 2321-2327, 2010

Highly Stable, Edible Cellulose Films Incorporating Chitosan Nanoparticles

The need for biodegradable polymers for packaging has fostered the development of novel, biodegradable polymeric materials from natural sources, as an alternative to reduce amount of waste and environmental impacts. The present investigation involves the synthesis of chitosan nanoparticles-carboxymethylcellulose films, in view of their increasing areas of application in packaging industry. The entire process consists of 2-steps including chitosan nanoparticles preparation and their incorporation in carboxymethylcellulose films. Uniform and stable particles were obtained with 3 different chitosan concentrations. The morphology of chitosan nanoparticles was tested by transmission electron microscopy, revealing the nanoparticles size in the range of 80 to 110 nm. The developed film chitosan nanoparticles-carboxymethylcellulose films were characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis, solubility tests, and mechanical analysis. Improvement of thermal and mechanical properties were observed in films containing nanoparticles, with the best results occurring upon addition of nanoparticles with 110 nm size in carboxymethylcellulose films. Practical Application Carboxymethylcellulose films containing chitosan nanoparticles synthesized and characterized in this article could be a potential material for food and beverage packaging applications products due to the increase mechanical properties and high stability. The potential application of the nanocomposites prepared would be in packaging industry to extend the shelf life of products.

Effect of solvent on the adsorption behavior and on the surface properties of Sterculia striata polysaccharide

Characterization of Sterculia striate polysaccharide (SSP) films adsorbed onto Si wafers from solutions prepared in ethyl methyl imidazolium acetate (EmimAc), water or NaOH 0.01 mol/L was systematically studied by means of ellipsometry, atomic force microscopy and contact angle measurements. SSP adsorbed from EmimAc onto Si wafer as homogeneous monolayers (similar to 0.5 nm thick), while from water or NaOH 0.01 mol/L SSP formed layers of similar to 4.0 nm and similar to 1.5 nm thick, respectively. Surface energy values found for SSP adsorbed from EmimAc or water were 68 +/- 2 mJ/m(2) and 65 +/- 2 mJ/m(2), respectively, whereas from NaOH it amounted to 57 +/- 3 mJ/m(2). The immobilization of lysozyme (LYS) onto SSP films was also investigated. The mean thickness of LYS (d(LYS)) immobilized onto SSP films adsorbed from each solvent tended to increase with the decrease of gamma(P)(S) and gamma(total)(S). However, the enzymatic activity of LYS molecules was higher when they were immobilized onto SSP films with higher gamma(P)(S) and gamma(total)(S) values. (C) 2010 Elsevier Ltd. All rights reserved.

Thin films of carbohydrate based surfactants and carboxymethylcellulose acetate butyrate mixtures: Morphology and thermal behavior

Thin films of mixtures containing carboxymethylcellulose acetate butyrate (CMCAB) and carbohydrate based surfactant, namely, sorbitan monopalmitate (Span 40) or poly(oxyethylene) sorbitan monopalmitate (Tween 40) were spin-coated onto silicon wafers. The effect of surfactant concentration on resulting film morphology and surface toughness Was Studied by atomic force microscopy (AFM). Upon increasing the concentration of Span 40 in the mixture, films became rougher and more heterogeneous, indicating surface enrichment by Span 40 molecules. In the case of mixtures composed by CMCAB and Tween 40, the increase of Tween 40 in the mixture led to smoother and more homogeneous films, indicating compatibility between both components. Differential scanning calorimetry (DSC) revealed that Span 40 and Tween 40 act as plasticizers for CMCAB, leading to dramatic reduction of glass transition temperature of CMCAB, namely, Delta T(g) = -158 degrees C and Delta T(g)=-179 degrees C. respectively. (C) 2008 Elsevier B.V. All rights reserved.