Polymer Blend Thin Films Research Articles

Design and synthesis of high-performance polymer blend solar cell

Conducting polymer blend of poly ortho-anthranilic acid and poly ortho-phenylene diamine (PANPDA) doped with HCl was synthesized in an aqueous solution using ferric chloride as an oxidizing agent and sodium dodecyl sulfate as a template. This study extends prior research in the field by characterizing the synthesized polymer blend, employing techniques such as ATR-Raman spectroscopy, SEM, and XRD. According to XRD analysis, PANPDA exhibited an orthorhombic crystal structure with a Pnn2 space group, while SEM indicated an average crystallite size (D) of 154.1 nm. Optical properties and laser photoluminescence of PANPDA films were investigated. Geometrical analysis was performed using time-dependent density functional theory (TD-DFT) and optimization via TD-DFTD/Mol3 and Cambridge Serial Total Energy Bundle (TD-FDT/CASTEP). ATR-Raman, based on TD-DFT, revealed interactions between monomers leading to polymer blend nanofiber thin films. Within a wavelength range of 190–800 nm, the optical properties of PANPDA were studied. The direct energy gap calculated using TD-DFT was 1.875 eV. The refractive index had a maximum value of 1.93 at 1.63 for the polymer blend thin film. Laser photoluminescence spectra displayed an emission peak at λmax = 621.13 nm in PANPDA films. In the heterojunction Au/(PANPDA)/p-Si/Al, the fill factor (FF) and power conversion efficiency were found to be 41.60 % and 14.61 % at 240 W/cm2, respectively. The investigated optical energy bandgap in the nanofiber blend holds promise for various energy storage and solar cell applications.

Enabling quantitative analysis of complex polymer blends by infrared nanospectroscopy and isotopic deuteration.

Atomic-force microscopy coupled with infrared spectroscopy (AFM-IR) deciphers surface morphology of thin-film polymer blends and composites by simultaneously mapping physical topography and chemical composition. However, acquiring quantitative phase and composition information from multi-component blends can be challenging using AFM-IR due to the possible overlapping infrared absorption bands between different species. Isotope labeling one of the blend components introduces a new type of bond (carbon-deuterium vibration) that can be targeted using AFM-IR and responds at wavelengths sufficiently shifted toward unoccupied regions (around 2200 cm-1). In this project, AFM-IR was used to probe the surface morphology and chemical composition of three polymer blends containing deuterated polystyrene; each blend is expected to exhibit various degrees of miscibility. AFM-IR results successfully demonstrated that deuterium labeling prevents infrared spectral overlap and enables the visualization of blend phases that could not normally be distinguished by other scanning probe techniques. The nanoscale domain composition was resolved by fast infrared spectrum analysis. Overall, we presented isotope labeling as a robust approach for circumventing obstacles preventing the quantitative analysis of multiphase systems by AFM-IR.

Nanoscale friction force on thin films of polymer blends and silane layers matrix

In this paper, nanoscale friction measurements are obtained from the Atomic Force Microscope (AFM) cantilever tip interaction with the layer of polymer blends of Polymethyl Methacrylate (PMMA)/ Polystyrene (PS) (2:1 and 1:2 ratios), and silane (C8, C12 and C18) layers at different proportion. The contrast of these polymer blends is investigated from the simultaneous recording of the topographic and lateral forces imaging. The resonance frequency excitation method and the wedge calibrations are used to quantify the normal and the lateral force constant respectively. Then, the quantitative frictional forces are calculated from the obtained normal and lateral force constants. The nanonewton (nN) frictions are found to be dependent on the nano-dynamic properties of the tip-sample interaction, the proportion of the polymer matrix and silane layers, and the scan speed.

Hierarchical Self-Assembly and Chemical Imaging of Nanoscale Domains in Polymer Blend Thin Films

Self-assembly of polymers driven by intermolecular and intramolecular interactions leads to rich structural variations in thin films of polymer blends. In this work, ordering of poly(3-hexylthiophene-2,5-diyl) (P3HT) to form nanoparticles (NPs) and the self-assembly pattern of the NPs in poly(4-vinylpyridine) (P4VP) matrix are revealed by using scattering-type scanning near-field optical microscopy (s-SNOM). The P3HT NPs are formed spontaneously when the P3HT/P4VP/chloroform solution is spin-cast on unpatterned silicon wafer at room temperature. We find that the P3HT NPs organize within the P4VP matrix forming continuous stripes along the parallel striations, depending on the solution composition and spin-coating angular speed. The spacing between the parallel P3HT stripes that runs along the center of the ridges varies from sample to sample within 4–12 μm, whereas the width of the P3HT stripes confined within the ridges ranges from 0.2 to 1.1 μm as determined from the s-SNOM infrared phase contrast. The sizes of the P3HT NPs range from 5 to over 100 nm depending on the composition of the blend as determined by using an atomic force microscope after selectively dissolving the P4VP matrix. The smallest size observed in our experiment is significantly smaller than the smallest diameter (larger than 20 nm) reported in the literature. The results presented here show that interaction between immiscible polymers during solvent evaporation can be manipulated to control hierarchical self-assembly from molecular ordering to mesoscale dimensions, and high-resolution chemical imaging is necessary to resolve nanoscale domains so that solution processes can be optimized.

Optical, Electrical and Structural Characterization of MNA Doped PS: PVS Polyblends Thin Film

PS: PVC polyblend thin films doped with various concentration of Meta nitro aniline (MNA) (0.01 %, 0.05 %, 0.1 %, 0.5 %, 1 %, and 5 %) were synthesized by using the method of solution evaporation technique. The amorphous nature of doped thin film samples was confirmed by the X – Ray diffraction pattern which shows the decrease in intensity with the increase in the concentration of dopant. UV - vis spectra show increase in the absorption band with the increase percentage of dopant.The electrical conductivity study shows that the doping of MNA into the PS: PVC polymer blend thin film enhances its ionic conductivity with increase in temperature. This improved properties in the doped polyblend thin films are due to the increase in mobility of charge carriers.

Tuning phase separation morphology in blend thin films using well-defined linear (multi)block copolymers

Tuning phase separation morphology in polymer blend thin films is a promising strategy to improve their properties. In this study, a series of poly(n-butyl methacrylate)-b-polystyrene linear copolymers with the same overall degree of polymerization but different number of blocks are synthesized by macroRAFT-mediated emulsion polymerization, and used as compatibilizers in poly(n-butyl methacrylate)/polystyrene blend thin films with thickness of ca. 20 nm. It is verified that multiblock copolymer is more effective to diminish the size of phase separation domains compared to diblock copolymer. Self-consistent field simulation agrees with the experimental results, and demonstrates that the compatibilization behaviors of diblock and multiblock copolymers are different. Diblock copolymer can compatibilize the blend well at a higher content, whereas multiblock copolymers tend to give a smaller domain size but less homogeneous morphology. In addition, simulation results show that copolymers with a longer block length would produce a narrower interface, which may weaken the penetration of block copolymers into their corresponding phases. This study provides a pioneering attempt in clarifying the effect of block copolymers on blend phase separation morphology, and it will be of practical value in obtaining desirable mechanical properties of polymer thin films.

An experimental setup for dip-coating of thin films for organic solar cells under microgravity conditions.

We report the design and testing of a custom-built experimental setup for dip-coating from volatile solutions under microgravity conditions onboard an aircraft. Function and safety considerations for the equipment are described. The equipment proved to work well, both concerning the safety and the preparation of thin films. No leakage of the solvents, nor the solvent vapors, was detected, not even in a situation with a fluctuating gravitational field due to bad weather conditions. We have shown that the equipment can be used to prepare thin films of polymer blends, relevant for organic solar cells, from solution in a feasible procedure under microgravity conditions. The prepared films are similar to the corresponding films prepared under 1 g conditions, but with differences that can be related to the absence of a gravitational field during drying of the applied liquid coating. We report on some introductory results from the characterization of the thin films that show differences in film morphology and structure sizes.

Analysis of Homopolymer Distribution in a Polymer Blend Thin Film by Anomalous Grazing Incidence Small-Angle X-ray Scattering at the Bromine K-Edge

Polystyrene-block-poly(4-hydroxystyrene) (PS–PHS)/poly(4-hydroxystyrene) brominated (Br-PHS) blend thin films were analyzed using anomalous grazing incidence small-angle X-ray scattering (anomalous...

Improving Photophysical Properties of White Emitting Ternary Conjugated Polymer Blend Thin Film via Additions of TiO2 Nanoparticles.

The effect of TiO2 nanoparticles on the photophysical properties of ternary conjugated polymer (CP) blends of poly(9,9-dioctylfluorene-2,7-diyl) (PFO), poly 9,9-dioctylfluorene-alt-benzothiadiazole (F8BT) and poly(2-methoxy-5(2-ethylhexyl)-1,4 -phenylenevinylene (MEH-PPV) thin films was investigated. This ternary blend used a fixed amount of PFO as the donor with MEH-PPV and F8BT in various ratios as the acceptors. The solution-blending method and the spin-coating technique were used to prepare the blends and the thin films, respectively. Through efficient Förster Resonance Energy Transfer (FRET), the desired white emission was achieved with PFO/0.3 wt.% F8BT/0.5 wt.% MEH-PPV ternary blend thin film. Additions of nanoparticles up to 10 wt.% dramatically intensified the white emission which then dimmed at higher contents due to agglomerations. The current density–voltage characteristics of the nanocomposite thin films exhibited dependency on the content and distributions of the nanoparticles. Finally, a possible underlying mechanism for the intensification of emission is proposed.

Staining-free observation of polymer blend thin films on transmission extreme ultraviolet microscopy

Transmission extreme ultraviolet microscopy is applied to the staining-free observation of a poly(styrene–methyl methacrylate) (PS/PMMA) blend. At a photon energy of 92 eV, the imaginary part of the atomic scattering factor for oxygen, which represents the absorption, is four-times larger than that of carbon, and microstructures can be visualized by the contrast resulting from the presence of oxygen. Based on the signal to noise ratio of the images, we consider the optimum photon energy and sample thickness for common polymer blends. Finally, a practical high contrast of 30% is successfully demonstrated for the PS/PMMA thin film.

Solvo-selective imprinting of a thin polymer blend film for creating multi-length scale patterns

Controlling and spatial ordering of the phase separation in ultra-thin polymer-blend films is a viable approach to create complex surface structures with unique properties. This study reports a facile solvo-selective patterning technique in a phase-separated polymer blend thin film comprising of immiscible polymers polystyrene (PS) and poly(methyl methacrylate) (PMMA). The pattern replication was achieved using capillary force lithography by imprinting the blend films with cross-linked polydimethylsiloxane stamp with grating patterns. The replication was done in the presence of 1-chloropentane or acetic acid vapours, which are selective solvents for PS and PMMA, respectively. This engendered capillary flow of only one phase while the domains of the second phase remain rigid. Depending on the initial as-cast morphology of the film which is a function of the relative proportion of PS and PMMA, a variety of structures were obtained by combining the phase-separated domains with the structure imposed by the stamp. This method can be considered as a simple, one-step technique for creating hierarchical patterns that are likely to find applications in modulating properties of soft surfaces.

Circumventing Macroscopic Phase Separation in Immiscible Polymer Mixtures by Bottom-up Deposition

Achieving intimate mixing in immiscible polymer blend thin films is of paramount importance for maximizing their performance in numerous applications such as membranes, electronics, and energy devi...

Flexible Organic Electrolyte-Gated Transistors Based on Thin Polymer Blend Films of Crystalline C8-BTBT and Amorphous PTAA

Thin films of polymer blends consisting of a crystalline small-molecular semiconductor, 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT), and an amorphous polymer semiconductor, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), are studied and applied to organic electrolyte-gated transistors (OEGTs). The compositions can be easily controlled by adjusting the mixing ratios of the solutions in chloroform. In the thin-film state, PTAA acts as a structural matrix and a charge-transport bridge for C8-BTBT grains. The C8-BTBT:PTAA blends have a compositional effect on the thin-film properties and performance of OEGTs. As a result, the C8-BTBT:PTAA blend films with weight ratios of 8:2 exhibit a hole mobility twice that of pristine C8-BTBT films. Moreover, OEGTs based on the C8-BTBT:PTAA blend exhibit better charge-transport properties on flexible plastic substrates under bending conditions, compared to flat devices.

Measurement and modelling of tensile moduli of polymer blend thin films with phase separated structures

The mechanical properties of polymer composite thin films are critically important to their applications, but its investigation is still far from complete. In this study, phase separated polyurethane/polystyrene blend thin films with a variety of thicknesses ranging from ~135 to ~675 nm are mainly employed, and their apparent moduli are measured by tensile testing on water surface. Unlike bulk materials, the phase height difference is a common topography in blend thin films, which causes an unavoidable deviation between the measured moduli and the predicted values calculated from any existing model. An equivalent box model with void geometry is developed to describe the polymer blend thin films with a cratered morphology, where both the composition and the phase structure of the dispersed phase are considered. The predicted values from the new model demonstrate a good agreement with the measured moduli. In addition, thin films with both components in rubbery state or both components in glassy state are tested, and the validity of the proposed model is verified as well.

The interplay of thermodynamics and kinetics: imparting hierarchical control over film formation of self-stratified blends.

Spin casting has become an attractive method to fabricate polymer thin films found in organic electronic devices such as field-effect transistors, and light emitting diodes. Many studies have shown that altering spin casting parameters can improve device performance, which has been directly correlated to the degree of polymer alignment, crystallinity, and morphology of the thin film. To provide a thorough understanding of the balance of thermodynamic and kinetic factors that influence the stratification of polymer blend thin films, we monitor stratified polymer blend thin films developed from poly(3-hexylthiophene-2,5-diyl) and poly(methyl methacrylate) blends at controlled loading ratios, relative molecular weights, and casting speed. The structures of these thin films were characterized via neutron reflectivity, and the results show that at the fastest casting speed, polymer-polymer interactions and surface energy of the polymers in the blend dictate the final film structure, and at the slowest casting speed, there is less control over the film layering due to the polymer-polymer interactions, surface energy, and entropy simultaneously driving stratification. As well, the relative solubility limits of the polymers in the pre-deposition solution play a role in the stratification process at the slowest casting speed. These results broaden the current understanding of the relationship between spin casting conditions and vertical phase separation in polymer blend thin films and provide a foundation for improved rational design of polymer thin film fabrication processes to attain targeted stratification, and thus performance.

Fabrication of complex polymer nanostructures from thin polymer blend films

We systematically investigated the morphological evolution of thin polymer blend films via annealing in mixed solvents. Here, a simple and efficient approach was proposed to fabricate different complex polymer nanostructures based on the dewetting of polymer blend films in mixed solvent. First, the nanobowl structures of poly(methyl methacrylate) and π-conjugated polymer-poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] were fabricated using this method. In addition, we also found that reversible dynamic transition among complex polymer structures could be achieved. This allowed us to reversibly adjust the complex structures by different external stimuli. Finally, it was determined that various arrays of complex polymer nanostructures, such as Janus nanostructures, core-shell nanostructures, nanobowls, nanochannels, and nanotubes, could be fabricated by pre-patterning the thin polymer blend films.

Effect of Mixing on the Optical Parameters of Polymer Blend (PMMA:PVC:PS) Thin Films

The thin films have been prepared using casting method at normal weather conditions of pressure and temperature. The films treated thermally for three hours at 45 °C. The UV-VIS double beam technique used to determine absorption and reflection spectrum. The thickness of the prepared thin films is measured using a handheld gauge of coating thickness measurement. Excel and MATLAB program used to calculate and simulate parameters and figures. The optical properties of PMMA:PVC:PS mixtures have been investigated. There is a clear change in the optical parameters due to mixing ratio. The result shows the indirect energy gap values reduced from 1.58 to 1.9 electron-volts. Mix a ratio of PMMA, PVC & PS leads to enhance some of the optical parameters like optical energy gap, absorbance, extinction coefficient and optical conductivity. The four kinds of thin films have different properties: The polymer blend (50%PMMA:25%PVC:25%PS) has the smallest values of the energy gap and linear refractive index, and the highest extinction coefficient values. The polymer blend (25%PMMA:25%PVC:50%PS) has a small value of energy gap and the best optical conductivity. The polymer blend (25%PMMA:50%PVC:25%PS) has the highest Urbach energy and absorption for the short wavelength (370 to 620 nm). The polymer blend (50%PVC:50%PS) has a good reflection, linear refractive index and skin depth, but it has the lowest values of extinction coefficient and optical conductivity.

Fullerene Aggregation in Thin Films of Polymer Blends for Solar Cell Applications.

We report on the effects of the film morphology on the fluorescence spectra for a thin film including a quinoxaline-based co-polymer (TQ1) and a fullerene derivative ([6,6]-phenyl-C71-butyric acid methyl ester—PC70BM). The ratio between the polymer and the fullerene derivative, as well as the processing solvent, were varied. Besides the main emission peak at 700 nm in the fluorescence spectra of thin films of this phase-separated blend, a broad emission band is observed with a maximum at 520–550 nm. The intensity of this emission band decreases with an increasing degree of mixing in the film and becomes most prominent in thicker films, films with high PC70BM content, and films that were spin-coated from solvents with lower PC70BM solubility. We assign this emission band to aggregated PC70BM.

Cavitation Erosion Behavior on Thin Films of Polymer Blends Deposited Over Bronze Surfaces

The composite materials with polymeric matrix represent a great realization of chemical engineering. Their applications in all the industrial fields are dictated by their chemical, physical and mechanical properties. In the last 50 years the polymeric composite materials received a large use in the protection and repair work of the surfaces in contact with fluid currents of various natures. The scientific researches followed by the industrial use, show that the polymere films with certain composition and properties have an excellent behavior to chemical, abrasive and cavitation erosions. Because the most stressed machine details subjected to cavitation erosions are the blades, runners and impellers of hydraulic machines as well as the ship propellers, researchers are looking for the best polymers to increase the running time, or for the use in covering the zones with shallow erosions, during the repair work. In this direction is oriented also the present research, performed in the Cavitation Laboratory of the Timisoara Polytechnic University. The obtained cavitation erosion for specimens covered with different polymere films is compared with those realized in identical conditions, but for specimens without protection films. The results show that the films assure some increase in the resistance to cavitation erosion but the tested polymer layers have reduced adherence on the metal surface.

Bottlebrush Copolymer Additives for Immiscible Polymer Blends

Thin films of immiscible polymer blends will undergo phase separation into large domains, but this behavior can be suppressed with additives that accumulate and adhere at the polymer/polymer interface. Herein, we describe the phase behavior of polystyrene/poly(methyl methacrylate) (PS/PMMA) blends with 20 vol % of a bottlebrush additive, where the bottlebrush has poly(styrene-r-methyl methacrylate) side chains with 61 mol % styrene. All blends are cast into films and thermally annealed above the glass transition temperature. The phase-separated structures are measured as a function of time with atomic force microscopy and optical microscopy. We demonstrate that subtle changes in bottlebrush architecture and homopolymer chain lengths can have a large impact on phase behavior, domain coarsening, and domain continuity. The bottlebrush additives are miscible with PS under a broad range of conditions. However, these additives are only miscible with PMMA when the bottlebrush backbones are short or when the PMMA...