The influence of surfactants on the structure of transparent gelatin films

The interference image of cold-dried transparent gelatin films containing different surfactants was determined in the conoscopic ray of monochromatic light. From the results obtained the order of the structure of gelatin in the film was characterized. Unlike the ionic surfactants (sodium dodecyl sulfate and hexadecyltrimethyl ammonium bromide), which lead to a reduction of the ordered structure, the addition of nonionic and amphoteric surfactants [ethoxylized octylphenole and a technical C₁₂/C₁₄-dipoly(oxyethylene)ammoniopropane sulfonate] causes an increase of the ordered structure of gelatin. The results quantitatively agree with those found for the influence of surfactants on the secondary structure of gelatin in diluted gelatin solutions. The influence is independent of the gelatin/surfactant ratio and has been explained by gelatin/gelatin interaction competing with the gelatin/surfactant interaction if the gelatin concentration becomes sufficiently high.     

The optical rotation of gelatin films

Optical rotation measurements of a series of relatively thick gelatin films prepared under a variety of drying conditions were made. The technique permits rotation measurements to be made during the drying process. It is found that the temperature and humidity of the drying air do not significantly affect the rotation of the films at temperatures below about 25°C. wet bulb. Above this temperature the rotation drops sharply. Films containing formaldehyde and mucochloric acid as hardeners tend to have lower rotations than unhardened films. Various types of gelatin show differences in the gel state, but not when dried. The results of these experiments indicate that in general gelatin tends to acquire the same level of ordered structure during drying, regardless of the drying conditions and type of gelatin. This tendency is inhibited only by high temperatures or the establishment of stable intermolecular crosslinks by hardeners.     

Dynamic surface tensiometry of tissues using Langmuir films

Langmuir monolayers are useful models of biomembranes as they allow simulation of biological conditions and rigorous thermodynamic analysis. This technique was used to characterize tissues at body temperature for the first time in our study. The organs studied include liver, kidney, stomach, testis, heart and brain from goat and certain human cancerous as well as their corresponding normal biopsies to reveal the potential of the tissue monolayer technique. Monolayers were formed on the surface of deionized water by spreading monolayer amounts of the tissue homogenates. The parameters calculated were minimum surface tension, relative lift off area, relative limiting area, compressibility and hysteresis area. Our results reveal that the parameters can differentiate between tissues obtained from different organs and were statistically significant using one-way ANOVA and Newman Keul's test (P<0.05). For example goat's stomach tissue had the lowest hysteresis area (DeltaG) value (27.6 microJ) whereas brain DeltaG value was nine folds higher than stomach value. Brain had the lowest minimum surface tension of 30.3+/-1.0 mN/m whereas stomach had a value of 40.5+/-0. 2 mN/m. Interestingly, the DeltaG values of human normal neck and esophageal tissues were 3.4 and 3.2 folds greater than that of their respective cancer tissues whereas the DeltaG values of vulval and breast cancer tissues were 4.6 and 4 folds greater than that of their respective normal tissues. While the gammamin values of neck cancer tissue showed 95% increase from normal tissue values, those of vulval and breast cancer tissues were 46 and 50% less compared to their respective normal tissue values. Though all the surface tensiometric parameters showed significant changes, minimum surface tension and hysteresis area were the most sensitive indicators of tissue types and diseased states. Further, the effects of therapeutics could also be monitored by this technique. This is evidenced by the post-radiotherapy tissue isotherms of neck and vulval cancers, where clinical radio-sensitivity was associated with a shift in the tensiometry towards their respective normal isotherms. The small sample amounts required, precision of the technique, very low within group variability, organ specificity and sensitivity to detect changes in diseased states make it a promising tool for prognostic evaluation of diseased states and monitoring effects of therapeutics. Further research is warranted in this promising and hitherto unexplored field of tissue tensiometry.     

Magnetism and surface structure of atomically controlled ultrathin metal films

We review the correlation of magnetism and surface structure in ultrathin metal films, including the tailoring of novel magnetic properties using atomic scale control of the nanostructure. We provide an overview of modern fabrication and characterization techniques used to create and explore these fascinating materials, and highlight important phenomena of interest. We also discuss techniques that control and characterize both the magnetic and structural properties on an atomic scale. Recent advances in the development and applications of these techniques allow nanomagnetism to be investigated in an unprecedented manner.A system cannot necessarily retain a two-dimensional structure as it enters the ultrathin region, but it can transform into a three-dimensional, discontinuous structure due to the Volmer–Weber growth mechanism. This structural transformation can give rise to superparamagnetism. During this evolution, competing factors such as interparticle interactions and the effective magnetic anisotropy govern the magnetic state. These magnetic parameters are influenced by the nanostructure of the film. In particular, controlling the magnetic anisotropy is critical for determining the magnetic properties. Surface effects play especially important roles in influencing both the magnitude and direction of the magnetic anisotropy in ultrathin films. By properly altering the surface structure, the strength and direction of the magnetic anisotropy are controlled via spin–orbit and/or dipole interactions.     

Deterioration of surface structure of lacquer films due to ultraviolet irradiation

The mechanism of deterioration due to ultraviolet irradiation of black (with iron ion) and kurome (translucent) lacquer films that had been dried at 15–20 °C in 60–70% relative humidity environment was revealed. The lacquer film changes were evaluated by observations of the surface by microscopy, IR, and XPS. A particulate material and toroidal shapes appeared in the black lacquer film during UV irradiation within 48 h, but they did not appear in the kurome lacquer film under UV irradiation before 240 h. The IR peak at ～3445 cm^?1 increased owing to the hydroxyl group, and the C 1s peak decreased and O 1s increased in the XPS spectra as the UV irradiation time increased, implying that a chemical reaction occurred on the surface of the lacquer film. On the top surface of the coating film, many toroidal shapes were observed in the black lacquer film, which showed that the black lacquer film deteriorated more quickly than the kurome lacquer film. In addition, the structural changes in the black lacquer film are also discussed in detail, on the basis of the results of the Py‐GC/MS measurement. Copyright © 2006 John Wiley & Sons, Ltd.     

The linear expansion of gelatin films by moisture sorption

Summary The gelatin films which are cast from water solutions have an anisotropy which disappears by annealing. The linear expansibility depends on theph of solutions, and on the temperature, films are dried, or on the hardening and on the contents of ash. Both specimens (hardening and non-hardening) in which theph is close to the iso-electric point have the minimum linear expansion. The high temperature film has more expansibility than the low temperature film.

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Zusammenfassung Gelatinfilme, aus w?\riger L?sung gegossen, sind anisotrop, Die Anisotropie l?\t sich durch Temperatur-Feuchtigkeit-Behandlung beseitigen. Das lineare Ausdehnungsverm?gen ist vomph der L?sungen, der Trockentemperatur, sowie von H?rtung und Aschegehalt abh?ngig. Beide Sorten der Filme (geh?rtete sowie nicht geh?rtete) dehnen sich um so weniger, je n?her derph-Wert dem des isoelektrischen Punktes liegt. Die bei h?herer Temperatur gefertigten Filme dehnen sich st?rker als die bei niedrigerer Temperatur bereiteten.

     

Novel methodology to control the adsorption structure of cationic porphyrins on the clay surface using the "size-matching rule"

Saponite-type clays that have different cation exchange capacities were successfully synthesized by hydrothermal synthesis. The structure and properties were analyzed by X-ray diffraction, X-ray fluorescence, (27)Al NMR, FT-IR, thermogravimetric and differential thermal analysis, atomic force microscopy, and cation exchange capacity measurement. The intercharge distances on the synthetic saponite (SS) surfaces were calculated to be 0.8-1.9 nm on the basis of a hexagonal array. The complex formation behavior between SS and cationic porphyrins was examined. It turns out that the average intermolecular distance between porphyrin molecules on the SS surface can be controlled, depending on the charge density of the SS. In the case of tetrakis(1-methylpyridinium-4-yl)porphyrin (H(2)TMPyP(4+)), the average intermolecular distances on the SS surface can be controlled from 2.3 to 3.0 nm on the basis of a hexagonal array. It was also found that absorption maxima of porphyrins depend on the charge density of the SS. The adsorption behavior of porphyrin on the SS surface can be rationally understood by the previously reported "size-matching rule". This methodology using host-guest interaction can realize a unique adsorption structure control of the porphyrin molecule on the SS surface, where the gap distance between guest porphyrin molecules is rather large. These findings will be highly valuable to construct photochemical reaction systems such as energy transfer in the complexes.     

Studies on the particle size control of gelatin microspheres

A series of gelatin microspheres (GMs) were prepared through emulsification-coacervation method in water-in-oil (w/o) emulsions. The influence of preparation parameters on particle size, surface morphology, and dispersion of GMs was examined. The studied preparation parameters include concentration of gelatin solutions, concentration of the emulsifier, w/o ratio, emulsifying time, stirring speed, and so on. The surface morphology, dispersion, and particle sizes of GMs were determined by the scanning electron microscopy (SEM), SemAfore 4 Demo software, and particle size distribution graphic charts. The experimental results indicated that increasing the concentration of gelatin solution would increase the particle size of GMs. When the solution concentration increased from 0.050 to 0.200 g/mL gradually, the particle size increased correspondingly. The relationship between the two quantities was linear. On the contrary, increasing the concentration of the emulsifier would decrease the particle size of GMs. Furthermore, the particle size reduced quickly at initial time and slowed down latterly. With the increase of emulsifier concentration from 0 to 0.020 g/mL, themean diameters ofGMsdecreased from 17.32 to 5.38 μm. However, the particle size dwindled slowly when emulsifier concentration was higher than 0.020 g/mL. The excellent result was obtained with the condition of 0.050 g/mL of emulsifier concentration, 0.100 g/mL of gelatin solution concentration, 1/5 of w/o ratio, 10 min of emulsifying time, and 900 r/min of the stirring speed. The GMs prepared at this condition had the smallest sizes, the narrowest size distribution, the best spherical shape, and fluidity. The w/o ratio has the same influence on particle size of GMs as that of gelatin solution concentration. With the increase of w/o ratio, the average particle sizes increased linearly, and the surface of microspheres become smoother as well. It is supposed that w/o ratio can be used to change the diameters and surface morphologies of GMs. The emulsifying time has little influence on the mean diameters of GMs, but it affects the dispersion of GMs apparently. When the emulsifying time was shorter than 5 min, the GMs had bad dispersion. After increasing the emulsifying time to 13 min, the dispersion of GMs changed greatly, whereas the dispersion of GMs became bad again when the emulsifying time was longer than 13 min. According to the experimental results, 13 min was considered to be the best emulsifying time. The stirring speed has the similar influence on GMs’ morphologies as that of emulsifying time. Slow stirring rate made large size distribution and bad spherical shape of GMs; excessive stirring speed results in aggregation among GMs likewise. The smaller size distribution and better spherical shape of GMs were observed under the stirring rate between 500 and 1500 r/min by SEM. In conclusion, increasing the concentration of gelatin solution or w/o ratio would increase the particle sizes of GMs, increasing the concentration of the emulsifier would decrease the sizes of GMs at proper emulsifying time, and stirring speed would get the best spherical shape of GMs. These are the basic laws governing the design and manufacture of the GMs. __________ Translated from Acta Polymerica Sinica, 2008, 8 (in Chinese)     

Characterization of the surface structure of gold nanoparticles and nanorods using structure sensitive reactions

The surface structure of gold nanorods has been determined by studying the behavior of electrochemical reactions sensitive to the structure and compared to that obtained by other structure characterization techniques. Lead underpotential deposition (UPD) reveals that the surface of the nanorods is composed by (111) and (110) domains, while (100) domains are practically absent from the surface. In the case of the oxygen reduction reaction, the formation of hydrogen peroxide as a final product of the reaction in the whole potential range also indicates that (100) domains are absent on the surface of the nanoparticles, corroborating the previous result. These results are compared with other surface structure information provided by other techniques.     

Response surface methodology (RSM) of chicken skin gelatin based composite films with rice starch and curcumin incorporation

This study aims to optimize the formulation of composite films based on chicken skin gelatin with incorporation of rice starch (10–20%, w/w) and curcumin (0.03–0.10%, w/v). The effect of their interaction on film's tensile strength (TS), elongation at break (EAB), water vapor permeability (WVP) and antioxidant properties (DPPH%) were investigated using a response surface methodology-central composite design (RSM-CCD). The optimized film formulation was further validated to indicate the validity of the prediction model. The optimum conditions of the film were selected with incorporation of rice starch at 20% (w/w) and curcumin at 0.03% (w/v). The optimized film formulation has revealed better mechanical properties with low WVP value and good antioxidant activity. The results showed that optimized composite films formulation based on chicken skin gelatin with the incorporation of rice starch and curcumin has proving good validation of model prediction and can be effectively utilized in food packaging industry.     

Preparation and surface activity of gelatin derivative surfactants

Surface active gelatin derivative surfactants were formed by covalent attachment of hydrophobic groups to gelatin hydrolyzate molecules. The surface activity was evaluated by surface tension, wetting ability, emulsifying power and foaming properties. It was found that, the modified gelatins are more surface active than the gelatin hydrolyzate. The increase in hydrophobic chain length and the number of attached alkyl chains per gelatin hydrolyzate molecule leads to an increase in the surface activity. The modified gelatins also have high foaming ability and a high emulsifying ability, while the maximal surface activity is obtained by the C₁₂ modified gelatin. The emulsification properties of the gelatin derivative surfactants were also compared to that of sodium dodecyl sulfate (SDS) and polyoxyethylene nonyl phenyl ether (NP-9), both emulsifying ability were equivalent to the C₁₂ modified gelatin.     

Study of the interfacial structure in epoxy bilayer films using neutron reflection

The interfacial structure in thin epoxy bilayer films was investigated with neutron reflection. For each experiment, a mixture of crosslinker and deuterated resin was spun onto a chemically similar, fully cured, protonated epoxy film. The reflectivity measurements were performed before and after curing the top epoxy film. We focused on the extent of penetration of the components of the top layer into the network of the bottom layer. The effect of the cure temperature of each layer was examined. In addition, the effect of the initial molecular weight of the oligomers in the top layer was probed by the partial curing of the mixture before spinning. As deposited, the components of the top layer penetrated the bottom layer to an extent that was largely independent of the aforementioned factors. The principal observation was that an additional penetration occurred with curing. This additional penetration was dependent upon both the molecular weight of the top layer and the cure temperature of the top layer relative to the glass‐transition temperature of the bottom layer. A decrease in the thickness of the top layer with curing was also observed, which likely indicates some evaporation of oligomers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1709–1718, 2002     

Near‐surface structure formation in chemically imidized polyimide films

Free‐standing polyimide films are manufactured by the chemical imidization of linear, soluble polymeric precursors. The reactive solution is coated onto a heated substrate, peeled off after partial imidization, and then dried and cured as a free‐standing film. Adhesive bonds to the cast side of the final film more strongly than to the air side. Near‐surface elastic moduli of film samples were measured with a nanoindentation setup. Samples were annealed at different final temperatures. The air side of the samples annealed at 400 °C had a higher modulus of 1.4 GPa than the 0.8 GPa of the casting side. This difference diminished as the annealing temperature was raised to 460 °C. Polyamic acid and polyimide exhibit phase transitions from disordered, isotropic solutions to ordered, liquid‐crystalline states. A theoretical model of drying and curing demonstrates formation of a gradient in conversion and ordering: the air side vitrifies at a lower solvent content, lower conversion, and higher ordering; the casting side, at a greater solvent content, higher conversion, and less ordering. Subsequent high‐temperature drying and curing of the free‐standing films removes solvent, completes reaction, and nematically orders both sides. However, longer times and higher temperature annealing are needed to bring the two sides to their common equilibrium state of nematic order. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1824–1838, 2001     

Selective control of surface properties using hydrodynamic interactions

Using computational modeling, we design nano-structured surfaces able to selectively regulate interactions between microchannel walls and flowing colloid-polymer suspensions. Depending on the geometry of nanoscopic posts lining internal channel surfaces, suspended nanoparticles and polymeric chains can be either hydrodynamically attracted to channel walls or repelled to the bulk fluid.     

Dynamic control of surface energy and topography of microstructured conducting polymer films

Microstructured polymer surfaces, including conducting and insulating polymers, have been prepared to achieve electrochemical control of the surface energy and topography. The reported surface switches include pillar- and mesh-like surface patterns of polypyrrole (PPy), poly(3,4-ethylene-dioxythiophene) (PEDOT), and photoresists. The structures have been evaluated by contact angle measurements and optical and scanning electron microscopy to determine the surfaces characteristics. These microstructured polymer surface switches can be electrochemically modified from dewetting to wetting conditions, with a maximum associated change of the water contact angle from 129 degrees to 44 degrees . This contact angle switching was observed for samples in which dynamic control of the surface topography and surface tension was coupled. Control of topography was achieved with a dynamic height-switching range of more than 3 mum. In addition, dynamic control of anisotropic wetting is reported. Our experiments were carried out under conditions that are suitable for a biointerface, implying potential application in biotechnology and cell science. In particular, switching of the energy, chemistry, and topography of the surface, along with their associated orientation, are interesting features for dynamic (electronic) control of the seeding and proliferation for living cells. The technology reported promises for electronically controlled cell-growth within Petri dishes, well plates, and other cell-hosting tools.     

Absorption of water by thin, ionic films of gelatin

This paper discusses absorption of water by thin, dry films of gelatin. Experiments using a wet-stamping technique were performed to characterize water uptake in terms of (i) equilibrium profiles of the water density inside the gel and (ii) the kinetics of water absorption. It was found that, in contrast to pure gelatin films, which absorb water approximately uniformly, films of gelatin doped with ionic additives have exponentially decaying equilibrium water profiles. The process of water absorption by both doped and undoped gels was described by a theoretical model based on the minimization of grand potential functional. The results of this model are in agreement with the experiment.     

Effect of the topography of silver films on the structure of surface ensembles of 11-mercaptoundecanol

The effect of the topography of the silver surface on the formation of self-assembling monolayers of 11-mercaptoundecanol was examined. The metal surface was modified by nitric acid in the presence of hydrogen peroxide (deep etching (DE)) or aqueous malononitrile (chemical polishing (PE)). The adsorption properties of the monolayers differ significantly for the DE and PE surfaces and are a function of the ratio of functional hydroxyl groups available for reaction with analyte and hydrophobic segments of the hydrocarbon chain of the molecule. A correlation between the amount of adsorption and the analyte acidity was demonstrated. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 45, No. 2, pp. 98-103, March-April, 2009.