Электрон-фононное взаимодействие в композитах с колллоидными квантовыми точками: исследование методами люминесцентной спектроскопии и комбинационного рассеяния света

The temperature-dependent luminescence spectra were analyzed to determine the parameters of the electron-phonon interaction (Huang-Rhys factor and the average phonon energy) for nanocomposites with colloidal CdSe/CdS/ZnS quantum dots (deposited on the surface of a glass substrate and embedded in a thin polymer film of polyisobutylene, and in a frozen colloidal solution in toluene). The measured values of the parameters are analyzed in comparison with model calculations and data obtained using the low-frequency Raman spectroscopy. It is found that in the case of a vitrified colloidal solution of quantum dots in toluene, the matrix effect leads to a noticeable change in the parameters of the electron-phonon interaction.

Cold Spray of Metallic Coatings on Polymer Based Composites for the Lightning Strike Protection of Airplane Structures

Unlike their metal counterparts; composite structures do not readily conduct away the electrical currents generated by lightning strikes. Cost reduction and expected production growth of the next middle range airplanes require automated manufacturing process of polymer components. The development of an automated technology to metallize polymer based composite for lightning strike protection is the aim of the CO3 project (EU Grant agreement: ID831979). In this study; thermal and electrical conductivities of composites were achieved by cold spray deposition of Cu or Al coatings. Critical points to be addressed were substrate erosion during cold spray; lack of polymer-metal adhesion and poor deposition efficiency. Several strategies were tested: i) a thin polymer film was cocured at the substrate surface before cold spraying; to enable implantation of metallic particles in the film; helping coating build-up and protecting the fibers of the composite. ii) Cold spraying a mix of metal and polymer powders to improve coating adhesion and prevent fiber damage. iii) Supercritical Nitrogen Deposition technology; prior to cold spray; to mechanically anchor metallic particles into the polymer. Subsequent cold spraying of purely metallic coatings was more efficient and showed better adhesion. All coatings were tested in terms of adhesion strength and electrical conductivity.

Study of the Effect of Bending Deformation on the Performance of Flexible Polymer Layered Humidity Sensor

Humidity-sensitive polymer, namely poly(vinyl alcohol-co-vinyl acetal), was deposited on a flexible poly(ethylene terephthalate) (PET) substrate pre-covered with a sputtered Au:Pd thin layer in order to develop an optical flexible humidity sensor. The spin-coating method was applied for the thin polymer film deposition. The optical and sensing properties of the device were studied after repeated bending deformation in the range of 25−1000 times. Transmittance measurements at different levels of relative humidity were conducted in order to examine the sensing properties of the probed flexible sample. The influence of the number of bending deformations on the performance of the sensor is studied, and the possibility for its successful application is demonstrated and discussed.

Single-Mode Lasing in Polymer Circular Gratings

In recent years, conjugated polymers have become the materials of choice to fabricate optoelectronic devices, owing to their properties of high absorbance, high quantum efficiency, and wide luminescence tuning ranges. The efficient feedback mechanism in the concentric ring resonator and its circularly symmetric periodic geometry combined with the broadband photoluminescence spectrum of the conjugated polymer can generate a highly coherent output beam. Here, the detailed design of the ultralow-threshold single-mode circular distributed feedback polymer laser is presented with combined fabrication processes such as electron beam lithography and the spin-coating technique. We observe from the extinction spectra of the circular gratings that the transverse electric mode shows no change with the increase of incident beam angle. The strong enhancement of the conjugated polymer photoluminescence spectra with the circular periodic resonator can reduce the lasing threshold about 19 µJ/cm2. A very thin polymer film of about 110 nm is achieved with the spin-coating technique. The thickness of the gain medium can support only the zero-order transverse electric lasing mode. We expect that such a low threshold lasing device can find application in optoelectronic devices.

The interplay between bi-modal molecular weight distribution in polystyrene and humidity induces self-assembly of biomimetic micropillars/honeycomb morphology in the thin polymer film

<p>Segregation of polymer chains of different molecular weights is a well-known process. A traditional experimental approach of studying phase segregation in thin films composed of polymer blends with identical chemical compositions but different molecular weights was focused on functionalisation of chemical group or modification of end-group. In this study, however, a different approach was proposed. Polystyrene with bimodal molecular weight distribution, but no additional chemical modification was used. The films were prepared by spin-coating and the segregation between polystyrene phases was investigated by force spectroscopy. The solubility of bimodal polystyrene was explored. At the right molecular weight distribution and soluted in Methyl Ethyl Ketone, the phase segregation occurred. Introduction of moist airflow induced the separation of the lower molecular weight into micropillars and the heavier fraction self-organized into a honeycomb. As a result, an easy, fast, and effective method of obtaining micropillar/honeycomb morphologies was demonstrated. The mechanism of formation of such structures was explained. </p>

The interplay between bi-modal molecular weight distribution in polystyrene and humidity induces self-assembly of biomimetic micropillars/honeycomb morphology in the thin polymer film

<p>Segregation of polymer chains of different molecular weights is a well-known process. A traditional experimental approach of studying phase segregation in thin films composed of polymer blends with identical chemical compositions but different molecular weights was focused on functionalisation of chemical group or modification of end-group. In this study, however, a different approach was proposed. Polystyrene with bimodal molecular weight distribution, but no additional chemical modification was used. The films were prepared by spin-coating and the segregation between polystyrene phases was investigated by force spectroscopy. The solubility of bimodal polystyrene was explored. At the right molecular weight distribution and soluted in Methyl Ethyl Ketone, the phase segregation occurred. Introduction of moist airflow induced the separation of the lower molecular weight into micropillars and the heavier fraction self-organized into a honeycomb. As a result, an easy, fast, and effective method of obtaining micropillar/honeycomb morphologies was demonstrated. The mechanism of formation of such structures was explained. </p>

Exploiting the Interplay Between Bi-Modal Molecular Weight Distribution in Polystyrene and Humidity to Induce Self-Assembly of Biomimetic Micropillars/honeycomb Morphology in Thin Polymer Film

<p>Segregation of polymer chains of different molecular weights is a well-known process. A traditional experimental approach of studying phase segregation of thin films composed of polymer blends with identical chemical compositions but different molecular weights, was focused on functionalization of chemical group or modification of end-group. In this study however, a different approach was proposed, in which polystyrene with a bimodal molecular weight distribution but no additional chemical modification was implemented in order to examine and analyze its phase segregation. It was found that by choosing right molecular weight distribution it is possible to obtain controlled phase separation at short time interval and at microscale. By doing this, we have presented an easy, fast, effective and fully controlled method of obtaining biomimetic micropillar/honeycomb morphologies. In addition, the evaporation rate during spin-coating and the viscosity of a solution with a bimodal molecular weight distribution was studied.</p>

Exploiting the Interplay Between Bi-Modal Molecular Weight Distribution in Polystyrene and Humidity to Induce Self-Assembly of Biomimetic Micropillars/honeycomb Morphology in Thin Polymer Film

<p>Segregation of polymer chains of different molecular weights is a well-known process. A traditional experimental approach of studying phase segregation of thin films composed of polymer blends with identical chemical compositions but different molecular weights, was focused on functionalization of chemical group or modification of end-group. In this study however, a different approach was proposed, in which polystyrene with a bimodal molecular weight distribution but no additional chemical modification was implemented in order to examine and analyze its phase segregation. It was found that by choosing right molecular weight distribution it is possible to obtain controlled phase separation at short time interval and at microscale. By doing this, we have presented an easy, fast, effective and fully controlled method of obtaining biomimetic micropillar/honeycomb morphologies. In addition, the evaporation rate during spin-coating and the viscosity of a solution with a bimodal molecular weight distribution was studied.</p>

Exploiting the Interplay Between Bi-Modal Molecular Weight Distribution in Polystyrene and Humidity to Induce Self-Assembly of Biomimetic Micropillars/honeycomb Morphology in Thin Polymer Film

<p>Segregation of polymer chains of different molecular weights is a well-known process. A traditional experimental approach of studying phase segregation of thin films composed of polymer blends with identical chemical compositions but different molecular weights, was focused on functionalization of chemical group or modification of end-group. In this study however, a different approach was proposed, in which polystyrene with a bimodal molecular weight distribution but no additional chemical modification was implemented in order to examine and analyze its phase segregation. It was found that by choosing right molecular weight distribution it is possible to obtain controlled phase separation at short time interval and at microscale. By doing this, we have presented an easy, fast, effective and fully controlled method of obtaining biomimetic micropillar/honeycomb morphologies. In addition, the evaporation rate during spin-coating and the viscosity of a solution with a bimodal molecular weight distribution was studied.</p>