Polymer thin films Research Papers (original) (raw)

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- Materials Science, Nanotechnology, Nanoscience, Optical Properties

A capacitance model for the estimation of water uptake in polymeric coatings is presented.
The model is based upon a linear combination of the individual capacitances of the polymeric
phase, the water and the air contained in the coating. Experimental comparison of the model
with gravimetric data has revealed an improvement with respect to the classical equations.

In this research, oxidized sucrose, a novel aldehyde-based green cross-linker, endowed starch films with substantial improvement in both tensile strength and elongation, whereas many other cross-linkers did not. Starch films are usually weak, brittle, and highly moisture sensitive, and thus have restricted industrial applications. Cross-linking is one of the most common methods to tackle these problems. However, most of the available cross-linkers are either toxic, expensive, or with low cross-linking efficiencies. Oxidized sucrose is a green cross-linker with multiple aldehyde groups per molecule to cross-link starch molecules via forming hemiacetals/acetals. The starch films cross-linked with oxidized sucrose had tensile strength and breaking elongation of 23 MPa and 60%, respectively, exceeding the cross-linking results of many other cross-linkers. Oxidized sucrose cross-linking also substantially increased the stability of starch films in both water and formic acid. With activation energy as low as 33.22 kJ mol −1 , the cross-linking, a pseudo-first-order reaction, could occur readily. Mild cross-linking using oxidized sucrose might provide an alternative to promote industrialization of starch-based products.

- by Hazal Canisag Ozturk
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- Starch, Biodegradable Polymers, Polymer thin films, Modified Starch
- by IJERA Journal
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- Materials Science, Nanotechnology, Nanoscience, Optical Properties
- by Silvia Bossi
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- Polymer thin films

PVC (polyvinylchloride) Plastisol films immersed in electrolyte were studied by Electrochemical Impedance Spectroscopy (EIS)
and the data were fitted using one-time constant and two time constant equivalent circuits. Very often the electrical behavior of
these films is better represented by the second circuit. The first time constant can be associated with the film capacitance and is
independent of the immersion solution ionic mobility, whereas the second one could be related with charge separation inside the film
pores and depends on cation mobility. Since the physical meaning of the two time constants is acknowledged their presence in EIS
measurements should be taken into account when the results are analyzed.

- by António Castela and +1
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- Electrochemical Impedance Spectroscopy, Polymer thin films, Organic coatings, Plastisol
- by Mircea Ignat
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- Polymer thin films

Thin organic films based on poly-methyl-methacrylate (PMMA) polymer have been obtained by pulsed laser deposition (PLD) on silicon substrates. The films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and Raman spectroscopy (RS). We observed that the film composition and structure depend on the laser fluence and on the temperature of the substrate during deposition.

A poly(phenoxy-imine)/p-silicon rectifying device was fabricated and the current-voltage characteristics of the device were examined as a function of temperature in the 40–300 K range. The temperature dependence of the main parameters, namely, the barrier height (Φb), ideality factor (η), reverse current (I0) and series resistance (Rs), were investigated. It was seen that the Φb and the I0 values of the device increased with increasing temperature, while the η and the Rs values decreased. The temperature dependences of the Φb and the η were interpreted by the assumption of a Gaussian distribution of the barrier heights arising from barrier inhomogeneities that prevailed at the interface of the poly(phenoxyimine)/p-silicon. From ln(I0/T2) vs. 1/ηT plot, the values of the activation energy (Ea) and Richardson constant (A*) were calculated as 0.324 eV and 2.84×10-7 A cm-2K-2, respectively. The experimental value of the Rs from the forward current-voltage plots decreased with an increase in the temperature.

- by Haci O Demir
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- Barrier height, Polymer thin films, Ideality Factor, Poly(Phenoxy-Imine)

Mueller ellipsometry in the mid-infrared (IR) spectral range can be used to obtain information about chemical composition through the vibrational spectra of samples. In the case of very thin films <100 nm, the ellipso-metric spectral features due to vibrational absorption are in general quite weak, and sometimes they are hidden by the noise in the measured data. In this work, we present one method based on the use of optical spacers as a tool to enhance the sensitivity of IR Mueller ellipsometry. An optical spacer is a thin film made of a known material which is between the substrate and the layer of interest. We show that, when the thickness of the two layers fulfills a given condition, the spectral features due to vibrational absorptions are enhanced. We explain the enhancement effect in terms of the Airy formula. The theoretical discussion is illustrated with two examples. We analyzed polystyrene thin films deposited on silicon wafers. Some of the wafers were covered by a thin film of thermal silicon dioxide SiO 2 , which was used as a spacer. The results show the suitability of the proposed technique to overcome the lack of sensitivity in ellipsometric measurements when it comes to working with either very thin films or materials with low absorption.

- by Enrique Garcia-Caurel and +3
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- Polymer Surfaces - Interfaces and Thin Films, Infrared spectroscopy, Polymer thin films, Spectroscopic Ellipsometry
- by Alfred Cuschieri
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- Polymer thin films
- by Stephan Herminghaus
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- Polymer thin films

This work deals with adhesion of Escherichia coli O157:H7 and Salmonella enterica subsp. enterica serovar Typhimurium LT2 (S. Typhimurium LT2) on polyethylene glycol (PEG) coated tomato surfaces. PEG coating was characterized by water contact angle technique, scanning electron microscopy, and secondary ion mass spectrometry. It was shown that PEG films could physisorb on the tomato surfaces after the oxygen plasma treatment, which made some outermost layers of the surfaces hydrophilic. Bacterial adhesion on PEG coated tomato surface was studied by standard plate count, fluorescence microscopy, and scanning electron microscopy techniques. Fully covered PEG film reduced the bacterial attachment 90% or more in comparison to the bare tomato surface. The degree of bacterial attachment decreased exponentially with increasing PEG coverage. When desired, PEG film could be removed by rinsing with water. Overall, this work demonstrates the proof-of-concept that an ultrathin film of polyethylene glycol may be used to effectively inhibit the attachment of pathogenic bacteria on tomato surfaces.

- by ming zhang and +1
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- Polymer thin films, Edible Coatings, Bacterial Adhesion, Anti-adhesive

- by Dr. yılmaz şahin
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- Chemical Engineering, Materials Science, Barrier height, Polymer thin films
- by Gencho Danev
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- Polymer thin films
- by Abbass Hashim
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- Polymer thin films

Mechanical properties of a polymer blend change as a function of temperature, particularly near phase transitions. Normally, the modulus and damping of a blend are recorded for the entire sample. Here, we present atomic force microscopy results from local measurements of the individual components of a polymer blend. The data are collected either as images at a set temperature, or spectra of a small area on the surface as a function of temperature. Using lateral force microscopy on Langmuir-Blodgett films, we found unexpected friction anisotropies and asymmetries in the frictional behavior. The data were found not to be related to the hexagonal packing of the molecules, but rather related to a small molecular tilt.

- by G. Gremaud
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- Polymer thin films, Micromechanics and Microtribology

The effect of carbon ion induced alterations undergoing in PEN polymer were examined using the various doses. Samples of PEN polymer were irradiated by Carbon (85 MeV) ions with the fluence in the range of 1 x 10 11 –3 x 10 12 ions cm-2... more

- by Carmen Racles
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- Polymer thin films