We went further in this direction and were successful in imprinting macroscopic patterns on these polymer films by simultaneous chemical and photochemical polymerization of aniline in the presence of light at the air-water interface and chemical reagents in the bulk. The method makes use of simultaneous chemical and photochemical polymerization of aniline in the presence of light.
This may be due to the formation of multilayer structures followed by collapse and molecules entering the bulk phase, thus reducing the population of molecules per unit area for such a layer at the interface. This may have important applications for in situ studies on the formation of monolayer structures at air-water interfaces or others.
Introduction
Our direction
On the other hand in this chapter we report the observation of patterns in thin polymer films of PANI formed at the interface coupled with reactions in the bulk medium. We found that, if left undisturbed, anilinium sulfate in the presence of the BZ reaction mixture led to the formation of polyaniline in the bulk, which eventually settled to the bottom of the solution.
Experimental Section
- Film formation
- UV – visible spectroscopic studies
- FTIR spectroscopic studies
- Gel Permeation Chromatography
- Resistivity measurement
On the other hand, the polymer film formed at other parts of the air-water interface and in the bulk. There is some variation in the peak positions, however, depending on the nature of the reagents used.
Mesoscopic investigation of polymer film
When Mohr's salt-containing reagents were used, the polymer growth patterns had units of polygons of different shapes and sizes. When aniline was introduced from the vapor phase and Mohr's salt was used as a catalyst, patches of film where circles had coalesced to form lumps could be seen.
Effect of surfactant on the mesoscopic structures
In addition, similar variations were also observed in the same films, but at different locations of the slide.
Effect of sonication on macroscopic and microscopic patterns of film
We have also observed similar pattern formation when polymerization was carried out in the presence of Ce(III)-catalyzed BZ reaction. This is also consistent with our observation of circular patterned growth in the presence of SDS.
Conclusion
From the above observations, it is clear that patterning in the polymerization of aniline at the interface is not exclusive to the BZ reaction. We also reported the spontaneous formation of mesoscopic and macroscopic patterns in the films formed at the interface.
This could be well reflected in the pronounced role of SDS and ultrasound waves in pattern formation. Different mesoscopic patterning under different experimental conditions indicates the role of nucleation-like process in the patterning in the microscopic scale.
Introduction
Some of the Existing methods of photo-chemical pattern generation
Self-assembly into amphiphilic molecular monolayer formation is thermodynamically favorable and therefore requires less attention or special equipment than the preparation of a LB monolayer. Briefly, all the methods mentioned above involve the preparation of a film on a substrate followed by exposure to light of a certain wavelength to form the pattern required for a particular application.
Our approach
Here we report air-water interfacial polymerization of aniline coupled to reaction with acidic KBrO3/KBr in the bulk from below and in the presence of UV or visible light incident on a selected part of the interface from above. In other words, a polymer film was formed with an imprint in part of the film in the shape and size of the light beam.
Mirror
Experimental
After a few cycles of water draining and refilling, the film was carefully transferred to a glass slide. The molecular weight of the film was recorded using gel permeation chromatography data in a Waters HPLC-GPC system.
Results and Discussion
- Characterization of polymer film by Fourier Transform Infra-Red spectroscopic (FTIR) studies
- UV-Visible spectroscopic studies
- Gel Permeation Chromatography
- Thickness measurement
- Investigation of mesoscopic structures of the illuminated and non-illuminated parts of films
- Mechanism
UV-vis spectra of the air/water grown polymer film were also recorded. Molecular weight distribution graphs for illuminated (at 320 nm) and non-illuminated parts of the film are shown in Figure 3.7 and Figure 3.8, respectively.
Conclusion
In the absence of light, mesoscopic nucleation pattern in the polymer formation at the interface formed is characteristic of the polymerization initiator. The polymer growth is more in the photo-irradiated region of the interface and thus the thickness is more compared to the non-illuminated part.
The new technique of photolithography described here in thin polymer films formed at the interface between air and water may have a certain advantage over other methods, because the print is embedded in the film of the same material and it captures a wide range of wavelengths incident light can be used. Furthermore, the contrast in the optical density of the films could be tuned with the appropriate choice of polymer-forming materials.
Introduction
We were interested in the possibility of incorporation of TiO2 NPs into thin films of the well-studied conductive polymer polyaniline (PANI). In this chapter, we report a new method for generating PPy thin films at the air-water interface.
Experimental Section
- Preparation of TiO 2 nanoparticles
- Preparation of thin polymer film containing TiO 2 NPs
- Photocatalysis of the polypyrrole film containing TiO 2 NPs
UV-visible spectroscopic, electron microscopic, and X-ray diffraction methods were used to characterize the incorporation of TiO2 into the film. The film thus formed was carefully washed by constantly adding and draining water from the sides of the watch glass and then transferred to a clean glass slide.
Result and Discussions
We further performed powder X-ray diffraction measurements to confirm the presence of TiO2 in the film. Unfortunately, the signal from a single film with respect to XRD of TiO2 was too weak to be observed.
Wavelength (nm)d
It is well known that the photocatalytic oxidation of iodide ions (I -) produces iodine molecules (I2), which combine with iodide ions (I-) to form triiodide ions (I3-. ), which absorb light at 352 nm. After two hours of irradiation, as a result of the photooxidation of iodide (I-) ions, triiodide ions (I3-) were formed, which causes the appearance of absorbance at 352.
Time (minutes)
The decay percentage increased to 46.1% after 90 minutes of UV irradiation for TiO2 NP embedded polypyrrole film while for the same duration of irradiation the decay percentage in the presence of polypyrrole film was only 17.9. The graph clearly shows the degradation effectiveness of methyl orange in the presence of polypyrrole film containing TiO2 NPs compared to polypyrrole film alone.
Wavelength (nm)
- Conclusion
- References
- Introduction
- Fabrication Techniques
- Our strategy
- Experimental section
- Making single color pattern on different substrate .1 Preparation of Substrates and mold
The degradation of methylene blue is more pronounced in the presence of the polypyrrole film containing TiO2 NPs. We were able to show evidence for the presence of TiO2 NPs in the film by TEM and XRD methods.
Overhead Projector Paper Or Glass Slide
To obtain the sample, the mold was placed on the mark between 10 s and 20 s after making the mark. Immediately after placement on the mark, the mold was either finger pressed or pressed with a homemade screw press.
Mold Dye
They were used as substrates on which macroscopic lines were drawn using permanent marker pens (Luxor) of different colors. For patterns in single color, a macroscopic line mark was made on a glass slide or OHP paper with a permanent marker pen with colored ink.
Mold removed
Making two - colors sub-micron scale patterns on different substrates .1 Substrate and mold
- Methods
- A. Scheme1
- B. Scheme 2
For between 20 s and 30 s, the mold was pressed above the top mark and kept pressed for 5 min. The mold was then removed, after which the slide was checked under optical microscope for the quality of alternate parallel lines of different colors.
Glass substrate
In this scheme we made a macroscopic line with one color on the substrate as in scheme 1.
Mold sse
Stamped the mold on substrate which is blue
Injected red dye
C. Scheme 3
After removing the mold, the slide was checked with an optical microscope for parallel lines of one color as in one-color lithography. Then we pour diluted ink solution of another color (using a syringe) on one end of the slide so that the ink flows through the channels.
- Bi-color pattern
Here the print quality depends on the correct filling of the channels. Liquid filling and incorrect filling of the channels would reduce the clarity of the patterns.
Conclusion
In creating a two-color pattern, as in our previous method, we typically used portions of commercially available CD as a mold for creating parallel alternating lines of two colors. In addition, we used a colored liquid flow through the channels to obtain parallel alternating two-color lines.
The same idea can in principle be used to generate patterns of arbitrary shape determined by the nature of patterns on the stamps used to make the prints. One can imagine applications related to the current development in personal computer (PC) based data retrieval as a regular optical microscope can be incorporated as part of the computer to "read" information of sub-micron scale resolution, in color stored, written on various substrates.
Introduction
- Existing methods
- Our approach
Finally, the photoresist is removed to obtain the desired channel structure on the glass surface. Parallel lines as negative copies of the mold can be imprinted on the surface of the glass.
Experimental section .1 Substrate and mold
- Method
Results and discussions
The etching process would therefore take place both at the "hills" of the mold and the filled channels. As shown in Figure 6.8, we observed the formation of an "H" shaped mark on the glass plate, proving that etching of glass had indeed occurred by HF present in the "crests" and filled channels of the mold.
Conclusions
The advantage here is that although the HF in the "hills" of the shape would compete with those in the "valleys", due to the large volume in the "valleys", the effective pattern would be primarily due to the "valleys" ” and would therefore serve the purpose of channeling on the glass surface using the present method.
- Previous investigations
- Our study
The observations have been made with regard to the spread and recoil of the drop and the fate of the alcohol film. Thus, the concentration of surfactant in the droplet can affect the interfacial mixing of the droplet and the film.
Experimental section
Marangoni effect-driven flow can therefore also contribute to the spreading of the droplet. The camera was placed vertically above the droplet (about 4 cm from the glass plate) and was connected to a personal computer (PC).
Results and Discussion
However, here we show selected images of the drop from just after it was placed. As can be seen in the photographs, the diameter of the drop did not increase much at the beginning (first 25 s).
0 sec
60 sec 51 sec
70 sec
82 sec
100 sec
121 sec
210 sec
- Effect of the nature of alcohols on spreading and recoil
- Effect of surfactant concentration on spreading and recoil
- Effect of thickness of film on spreading
- Velocity distribution
- Composition of a dewetted drop
- What is really happening?
- D def
- D str C-D str
- Why does the drop recoil?
- References
- Experimental Section
Droplet removal on each alcohol film began immediately after complete spreading. Thus, the total spreading parameter is negative, which does not support the spreading of the droplet on the film.
UV-vis fibre optics probe
Result and discussion
The extinction is likely due to increased light scattering due to reef formation. We were further interested in whether the structure responsible for the light extinction prior to monolayer collapse was transient or stable.
Conclusion
On the other hand with the higher initial lipid concentration the phase transition occurred simultaneously with extinction of light (structure formation) at an area per molecule of 0.22 Å. These observations indicate that structures responsible for the extinction of light are formed at different phases and their transitions.
Various sophisticated and expensive microscopic techniques can show the exact nature of the film that constitutes a coating at different surface pressures. Additionally, the present technique may be useful to understand the nature of the monolayer in cases where in situ microscopy cannot be performed.
