Polymer Light Research Articles

The Study of Optical Energy Gap, Refractive Index, and Dielectric Constant of Pure and Doped Polyaniline with HCl and H2SO4 Acids

Polyaniline (PANI) salt in its pure and doped forms find extensive applications in making devices such as polymer light emitting diodes, photovoltaic, sensors, batteries, and super capacitors. PANI salt has been synthesized successfully through chemically oxidative polymerization of aniline in the presence of hydrochloric acid (HCl) and sulfuric acid (H2 SO4 ) using ammonium peroxydisulfate as an oxidizing agent. The absorption spectra of pure PANI salt and its doped state, in HCl and H2 SO4 media, have been studied in the wavelength range from 200 to 1100 nm using ultraviolet and visible near infrared spectrophotometer. Tauc’s formula, Lambert-Beer’s relation, and Fresnel’s formula were employed in the MATLAB program to calculate the optical energy gap, refractive index, and dielectric constant. Results showed that doping with HCl and H2 SO4 acidic mediums caused a reduction in the direct energy gap of the pure PANI from 2.69eV to 2.42 eV and 2.54 eV, respectively. The reduction in optical energy gap is associated with the increase in refractive index. The refractive index (2.92) has a higher value of PANI doped with HCl. Higher refractive index values are for better-structured films.

P‐165: Effect of Polarized Light Polymerization on Reflection Band Tunability in Polymer‐Stabilized Bimesogenic Cholesteric Liquid Crystal Devices

This work demonstrates approach for improvement of electro‐optic performance and light reflectance properties of electrically‐controlled reflective heliconical cholesteric liquid crystal (CLCoh) textures. A noticeable increase of the electric field range which supports the CLCoh texture is demonstrated by using photo polymerization with polarized UV light. Such performance improvement broadens the scope of potential applications of CLCoh materials in electro‐optical devices.

Structural, optical and electrical properties of ribbon-like graphene oxide thin films**Report presented at 9th International Workshop on Advanced Materials Science and Nanotechnology (IWAMSN2018), 7–11 November 2018, Ninh Binh City, Vietnam.

Graphene oxide is a unique material whereas it can be semiconductor or an insulating material depending on its degree of oxidation and dimensions. In this paper we report ribbon-like structure of spin-coated graphene oxide thin film with unusual optical and electrical characteristic. The films were prepared by spin coating technique with a variety of spin speed from 1000 rpm to 4000 rpm and annealed at 50 °C in a vacuum oven. Atomic force microscopy (AFM) revealed a ribbon-like structure with 32–200 nm. Further analysis by conductive AFM (C-AFM) showed an unexpected electrical conducting side at the edges of the ribbon-like structure. Optical characterization also unveiled the visible photoluminescence spectra at the peak wavelength of 397 nm while optical absorption estimates the band gap of 2.64 eV for each sample. The films were also tested as electron buffer layer in polymer light emitting devices and showed an enhancement of light intensity from 179 cd m−2 to 444 cd m−2 for 25 nm thin films. This shows the films have a high potential in optoelectronic applications.

New blue light emitting cyanopyridine based conjugated polymers: From molecular engineering to PLED applications

In this work, we report the design of three new cyanopyridine scaffold based polymers, viz. TPy1-3 as potential blue light emitters for PLED applications. The new polymer design comprise, a cyanopyridine core as an electron accepting entity, thiophene as an electron donating unit with different auxiliary donors, viz. phenylene (TPy1), biphenyl (TPy2), and fluorene (TPy3), and have been synthesized, following standard synthetic protocols including Suzuki-cross coupling polymerization reaction. Further, in order to assess all the prerequisites to act as an active emitter, the polymers TPy1-3, were subjected to structural, thermal, linear optical, electrochemical and computational studies. The results revealed that, all the polymers were thermally stable up to 300 ⁰C and their estimated optical band-gaps were found to be 2.59–2.80 eV. Finally, new polymer light emitting diode (PLED) were fabricated by employing the polymers TPy1-3, as active emissive material with a configuration of ITO/PEDOT: PSS/Polymer/Al. Interestingly, all the fabricated devices, exhibited an intense blue electroluminescence at 12 V with low threshold voltages of 4.2–4.8 V, signifying an effective injection of electron in the device.

Investigation of the Effect of Different Types of IPS e.max Press Porcelain on the Level of Polymerization of Light Cured Choice 2 Cement with FTIR Method

Investigation of the Effect of Different Types of IPS e.max Press Porcelain on the Level of Polymerization of Light Cured Choice 2 Cement with FTIR Method

Capacitance and impedance spectroscopy studies of polymer light emitting diodes based on MEH-PPV:BT blends

Light emitting polymer poly [2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) is blended with a wide bandgap electron transport material benzothiadiazole (BT) and its effect on the electronic properties has been studied by capacitance and impedance spectroscopy (IS) in PLEDs. The impedance data is fitted using equivalent circuit models and the minimum parallel resistance (Rp) at zero bias have been obtained for 1:3 ratio of MEH-PPV:BT blended devices. The negative capacitance (NC) shows the occurrence of the trap-assisted non-radiative recombination mechanism at low frequencies in the unblended MEH-PPV PLEDs. Further, this behavior is seen to be reduced in PLEDs with MEH-PPV:BT blends. This clearly suggests that the blending of MEH-PPV and BT at different weight ratios results in the suppression of trap-assisted recombination. This can be attributed to the elimination of trap states due to the dilution of semiconductor material on account of the addition of wide bandgap host material. Moreover, the blended devices have shown a significant improvement in the conductivity at small bias voltages.

Two interesting scaffolds derived from pyrazolo[3,4-b]quinolines: synthesis and applications

Pyrazolo[3,4-b]quinolines are fascinating compounds of great importance. They reveal not only a range of very interesting biological activities, but also have been applied as optical brighteners, in organic light emitting diodes (OLED), in polymer light emitting diodes (PLED), sensors, in nonlinear optics, solar cells and many others. Recently, two interesting scaffolds emerged from the basic ring system, the first group comprises analogues of azafluoranthenes, the second one contains a seven-member ring embedded in the main framework, which can give rise to chiral compounds to be used to the production of diodes emitting circularly polarized light (CPL).

Influence of Primers and Additional Resin Layer on Zirconia Repair Bond Strength.

To evaluate the influence of alloy/zirconia primer and 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-containing resin layer treatments on the shear bond strength (SBS) of composite resin to zirconia after aging. Sixty zirconia (Y-TZP) blocks were air-abraded (35-µm Al2 O3 ) and divided into 6 experimental groups (n = 10) in terms of primer/resin layer as follows: (1) control, without any primer or resin; (2) AP, Alloy Primer; (3) ZPP, Z-Prime Plus; (4) PL/ZPP, Z-Prime Plus with light polymerization; (5) AP+SEB, Alloy Primer along with light-cured bonding resin of a self-etch adhesive system (SE Bond); and (6) ZPP+SEB, Z-Prime Plus with SE Bond. After composite resin placement and light polymerization, the specimens were stored in distilled water (37°C for 4 months) and thermal-cycled for 6000 cycles. The SBS was tested with a universal testing machine. Statistical analysis of the SBS data was performed with one-way ANOVA, followed by HSD Tukey test (α = 0.05). There were significant differences between the groups (p < 0.001, F = 116.5). All the groups revealed significantly higher SBS than the control (p < 0.001). ZPP+SEB group exhibited the highest SBS (16.14 ± 2.52 MPa) and AP group the lowest SBS (7.00 ± 1.97 MPa) among experimental groups; both had significant differences with the other groups (p < 0.001). There were no significant differences between ZPP, PL/ZPP, and AP+SEB groups (p > 0.05). The bond strength between zirconia ceramic and composite resin was affected by different primers/resin layer. Applying an MDP-containing resin layer along with both primers resulted in significant enhancement of SBS. This improvement for Z-Prime Plus was significantly higher than that of Alloy Primer.

Influence of Monomer Systems on the Bond Strength Between Resin Composites and Polymerized Fiber-Reinforced Composite upon Aging.

This study examined the influence of different monomer systems on the tensile bond strength between a resin composite and a polymerized fiber-reinforced composite (FRC). The influence of the age (shelf-life) of the FRC prepreg (reinforcing fiber pre-impregnated with a resin system) before preparing the FRC substrate for the bonding test was also assessed. Semi-interpenetrating polymer network (semi-IPN)-based glass FRC prepregs were aged for various durations (1, 1.5, and 3 years) at 4°C before being used to prepare FRC substrates via light polymerization. Four groups of aged prepregs were prepared through different treatments with: 1. no primer; 2. a dimethacrylate-based adhesive primer; 3. a universal primer; and 4. a specific composite primer. Subsequently, a resin composite luting cement was applied on the treated FRC substrates and cured with light. The water sorption of the FRC-composite specimens was determined. Then, the differences in the tensile bond strength were evaluated using ANOVA (p ≤ 0.05). There were significant differences in the tensile bond strength between the composite cement and the FRC according to the primer used (p < 0.001), aging time (p < 0.001), and their interactive effect (p < 0.001). The monomers of the universal primer demonstrated the best ability to diffuse into the semi-IPN structure of the polymer matrix of FRC. This improved the interfacial bond strength between the composite cement and the FRC substrate.

Synthesis and properties of hyperbranched polymers for polymer light emitting devices with sunlight-style white emission.

A new series of hyperbranched polymers consisting of fluorene-alt-carbazole as the branches and the three-dimensional-structured spiro[3.3]heptane-2,6-dispirofluorene (SDF) as the core were designed and synthesized by one-pot Suzuki coupling polycondensation. A phosphor group with broad full width at half maximum (FWHM) bis(1-phenyl-isoquinoline)(acetylacetonato)iridium(iii) (Ir(Brpiq)2acac, 0.08 mol%) as the red-light emitting unit and bis(2-(4-bromophenyl)-1-[6-(9-carbazolyl)hexyl]-imidazole)(2-(5-(4-fluorinated phenyl)-1,3,4-triazole)pyridine)iridium(iii) ((CzhBrPI)2Ir(fpptz)) as the green-light emitting unit were introduced into the backbones to obtain sunlight-style white-light emission by adjusting the feeding ratios of (CzhBrPI)2Ir(fpptz) (0.08 to 0.32 mol%). The results indicate the synthesized polymers show high thermal stabilities and good amorphous film morphology because of the hyperbranched structures. Besides, the lowest unoccupied molecular orbital (LUMO) levels of polymers were reduced and the electron injection was improved because of excellent electron-transporting ability of the triazole unit in the green group. The hyperbranched structures can effectively suppress the polymers' chain distortion and aggregation, and promote the incomplete Förster resonance energy transfer (FRET) efficiency from fluorene-alt-carbazole segments to Ir complex units. As a result, the devices with hyperbranched polymer light-emitting layers realize white light emission, and the optimized device also exhibits good electroluminescent (EL) performance with Commission Internationale de l'Eclairage (CIE) coordinates at (0.32, 0.31), a maximum luminance of 9054 cd m−2, a maximum current efficiency of 3.59 cd A−1 and a maximum Color Rendering Index (CRI) of 91. The hyperbranched polymers based on fluorene-alt-carbazole branches and a SDF core and high-efficiency phosphor groups with broad full width at half maximum are attractive candidates for sunlight-style white polymer light-emitting device.

Using magneto-electroluminescence as a fingerprint to identify the spin polarization and spin-orbit coupling of magnetic nanoparticle doped polymer light emitting diodes.

The spin polarization and spin–orbit coupling (SOC) in polymer light emitting diodes (PLEDs) with the active layer doped with Fe3O4 nanoparticles (NPs) were identified through magneto-electroluminescence (MEL). By comparing the MEL characteristics such as linewidth and magnitude between PLEDs with and without Fe3O4 dopant, we confirmed the existence of spin polarization, but ruled out the existence of SOC. Although the spin polarization is positive to electroluminescence, the brightness–current characteristics suggested that the current efficiency of the doped PLED does not improve. We attributed it to the current leakage caused by the Fe3O4 NPs in the active layer. This work is beneficial for us to further understand the effect of magnetic nanoparticle doping on the dynamic behavior of excitons and polaron pairs in organic semiconductor devices.

Polymer light emitting diodes (PLEDs): An update review on current innovation and performance of material properties

Abstract Conventional lighting systems, such as the incandescent light bulbs used on the offshore oil rigs are becoming obsolete due to high energy consumption, poor life span and additional costs of waste treatment and disposal. Furthermore, they are susceptible to fire when exposed to an oxygen rich environment, posing a threat to the oil rig workers. Recent advances have led to the development of polymer light emitting diodes (PLEDs) as substitutes to these prevailing light sources. The PLEDs have advantages over the incandescent bulbs, for being durable, low energy consumption and environmental friendly. Consequently, the increasing research collaborations among the academic researchers and industrial stakeholders are gaining momentum in ensuring the advancements of PLEDs in terms of economic value and performance. This paper is aimed at reviewing the recent advances in the field of current innovation and performance of PLEDs materials. The paper focuses on the important experiments on the PLEDs materials towards the upgrading and modification of anode and holes injection/transporting layer and the influence of doping effect. In spite of that, this paper discovered that synthetic materials, such as synthetic silicates are the commonly used materials in the current PLEDs, and recommends the incorporation of cost effective inorganic clay-polymer nanocomposite-based LEDs as a way forward to reducing the material costs and provide more environmental friendly PLEDs materials.

Evaluation of the light transmission of chairside polymer infiltrated hybrid ceramics in different shades and thicknesses.

This in vitro study aimed to evaluate the amount of polymerizing light passing through hybrid ceramic specimens in different shades and thicknesses. Rectangular-shaped feldspathic ceramic computer aided design and computer aided manufacturing (CAD-CAM) blocks and translucent and high translucent polymer infiltrated hybrid ceramic CAD-CAM blocks in four different shades (1M1, 1M2, 2M2, and 3M2) were sectioned in four different thicknesses (0.8, 1.5, 2, and 3 mm), and a total of 48 groups ( n = 10) were obtained. Feldspathic ceramic specimens served as the control group. The light transmission of each ceramic specimen was measured three times by using a light-emitting diode and a radiometer. Data were statistically analyzed by using univariate analysis of variance (ANOVA) followed by one-way ANOVA, Tukey honest significant difference, and Tamhane T2 tests (α = 0.05). Translucent polymer infiltrated hybrid ceramic specimens exhibited significantly ( p < 0.001) lower light transmission values than high translucent polymer infiltrated hybrid ceramic and feldspathic ceramic specimens, whereas feldspathic ceramic specimens exhibited significantly ( p < 0.001) higher light transmission than translucent and high translucent polymer infiltrated hybrid ceramic specimens. The amount of light transmission significantly ( p < 0.05) decreased when the shade value decreased and the thickness increased. Polymer infiltrated hybrid ceramic specimens showed lower light transmission values than feldspathic ceramic specimens, and the amount of light transmission was affected by the ceramic shade and thickness.

Gingival microleakage of class II bulk-fill composite resin restorations.

Bulk-fill composites were developed to simplify composite placement and minimize polymerization shrinkage stresses, which can improve gingival marginal adaptation in deep class II cavities. The objective of this study was to compare the gingival microleakage of class II cavities restored with bulk-fill composites to that of incrementally restored ones with a conventional composite at 2 storage periods. Forty freshly extracted intact molars were employed. Two standardized class II slot cavities, 3-millimeter-wide buccolingually, with the gingival floor 0.5 mm below the cementoenamel junction (CEJ) and the axial wall depth of 1.3 mm were prepared in each tooth (80 cavity preparations). The prepared teeth were divided equally into 3 bulk-fill groups (Tetric EvoCeram® Bulk Fill, X-tra Fil® and QuiXX®) and 1 control group (TPH Spectra® HV). Each group was subdivided into 2 equal subgroups (n = 10) according to the storage period in distilled water (24 h and 6 months). The Adper® Single Bond Plus adhesive was used with all the restorative materials. The cavities in the experimental groups were restored with 4-millimeter bulk-fill composites in 1 increment, while the cavities in the control group were restored with 2 increments of the thickness of 2 mm. The polymerization light was applied from the occlusal surfaces. The teeth were then immersed in 2% procion red dye solution, sectioned and examined under a stereomicroscope to determine the extent of dye penetration. The data was statistically analyzed using the Kruskal-Wallis test and the Mann-Whitney U test. The Kruskal-Wallis test revealed no significant differences in the mean microleakage scores among all the groups after 24-hour and 6-month storage (p = 0.945 and p = 0.928, respectively). The Mann-Whitney U test revealed an increase in the mean microleakage scores in all the groups after 6-month storage; however, the scores were not significantly different from the means obtained after 24 h (p = 0.259 for Tetric EvoCeram Bulk Fill; p = 0.205 for X-tra Fil; p = 0.166 for QuiXX; p = 0.155 for TPH Spectra HV). Gingival microleakage of bulk-fill composites in class II cavities was not significantly different from that of incrementally restored ones with a conventional composite. The increase in the mean gingival microleakage of the specimens stored for 6 months was not statistically significantly different in comparison to the values obtained after the 24-hour storage period for each composite.

Machine-Washable Smart Textiles with Photothermal and Antibacterial Activities from Nanocomposite Fibers of Conjugated Polymer Nanoparticles and Polyacrylonitrile.

Smart textiles based on conjugated polymers have been highlighted as promising fabrics that can intelligently respond to environmental stimuli based on the electrical properties of polymer semiconductors. However, there has been limited interest in the photothermal properties of conjugated polymers that can be applied to smart textiles. We prepared nanoparticles by assembling a conjugated polymer with a fatty acid via an emulsion process and nanocomposite fibers by distributing the conjugated polymer nanoparticles in a polyacrylonitrile matrix. We then fabricated the textiles using the fibers. The resulting fabrics based on nanocomposite fibers show a temperature increase to 50 °C in 10 min under white light irradiation because of efficient photothermal conversion by the conjugated polymer light harvester, while the temperature of a pristine polyacrylonitrile fabric increases to only 35 °C. In addition, excellent antimicrobial activity was confirmed by a 99.9% decrease in the populations of Staphylococcus aureus and Escherichia coli over 24 h because of the effect of the fatty acid in the nanocomposite films and fabrics. Furthermore, the fabric showed efficient durability after a laundry test, suggesting the usefulness of these smart textiles based on conjugated polymer nanoparticles for practical applications.

A remote-controlled immunochemical system for nephelometric detection of human serum transferrin

The fully-mechanized Multicommutated Flow Analysis (MCFA) system for determination of transferrin in human serum has been developed. The analytical methodology concerns immunoprecipitation measurements with the use of LED-based nephelometric flow-through detectors with polymeric light guides. To improve the mechanization degree of the MCFA system, the Do-It-Yourself electronic module for mobile phone control has been developed. The design and structure of an Android software (build using open source application) controlling the operation of presented flow system has been presented. To bypass the problem of nonlinearity of calibration curve caused by the nature of antigen-antibody interactions, the on-line dilution module has been integrated into the presented manifold. Under optimized conditions, the developed flow analysis system is characterized by relatively low limit of detection and quantitation (2.0 and 4.9 mg L−1, respectively), good precision (RSD < 4%), low reagent and sample consumption per one measurement (16 µL of undiluted reagent and 20 µL of undiluted sample without further on-line dilution, respectively) and relatively high throughput (approximately 35 signal recordings per hour). The developed MCFA system enabled to analyze 16 serum samples with the transferrin concentration from 90 to almost 350 mg dL−1 with statistical agreement to the reference method.

Polymer Light Emitting Devices: High‐Speed OLEDs and Area‐Emitting Light‐Emitting Transistors from a Tetracyclic Lactim Semiconducting Polymer (Advanced Optical Materials 21/2018)

Polymer Light Emitting Devices: High‐Speed OLEDs and Area‐Emitting Light‐Emitting Transistors from a Tetracyclic Lactim Semiconducting Polymer (Advanced Optical Materials 21/2018)

Effect of previous photoactivation of the adhesive system on the color stability and mechanical properties of resin components in ceramic laminate veneer luting

Statement of problemThe color stability and mechanical properties of luting agents influence the esthetics and longevity of ceramic restorations. However, studies evaluating the color changes and mechanical properties of luting agents under ceramic laminates activated by using different methods are lacking. PurposeThe purpose of this in vitro study was to evaluate the effects of different modes of photoactivation on the nanohardness and elastic modulus of resin cements and dental adhesives and on the color stability of ceramic laminate veneers. Material and methodsForty-four lithium disilicate blocks (7×8×0.6 mm) were cemented onto bovine enamel and divided into 4 groups according to the polymerization light (Radii-Cal or Valo) used and the mode of activation of the dental adhesive (no previous photoactivation or previous photoactivation). Single Bond Universal dental adhesive and RelyX Veneer resin cement were used in all experimental groups. Color stability was measured using a UV-2450 ultraviolet-visible spectrophotometer before and after ultraviolet-B artificial accelerated aging (n=8). The nanohardness and the elastic modulus of the adhesive and resin cement were measured using a nanohardness tester (n=3). The color stability and mechanical properties were measured and analyzed using ANOVA and the Tukey least significant difference test (α=.05). ResultsNo difference in color stability or mechanical properties of the resin cement among the polymerization lights was detected (P>.05). Specimens that underwent previous photoactivation of the adhesive using the Valo polywave unit exhibited higher elastic modulus values than those that did not undergo previous photoactivation (P<.001). ConclusionsThe Valo polywave polymerization light improved mechanical properties and color stability more than the Radii-Cal unit. Previous activation of the dental adhesive in the dental enamel with the Valo polywave polymerization light yielded more satisfactory results.

Characterization of a new polymer optical fiber with enhanced sensing capabilities using a Bragg grating.

We present results for the mechanical characterization of a bisphenol-A acrylate-based polymer optical fiber (POF) manufactured using a novel light polymerization spinning (LPS) process. The particular manufacturing process allows the development of POFs having unique mechanical characteristics, which result from an exceptionally low Young's modulus. The lower Young's modulus enables optical sensors for measuring stress or pressure with improved sensitivity and potentially a higher tunable mechanical range than conventional POFs. Moreover, properties such as the storage modulus variations with respect to the temperature and humidity were studied. Fiber Bragg gratings (FBGs), were inscribed in the POF using the plane-by-plane femtosecond laser, direct-write method for selective FBG mode excitation, and were characterized for changes to temperature, pressure, and relative humidity. The response of FBGs in this LPS-POF for all the three aforementioned measurands was several times higher than that measured for conventional POFs.

Light-driven topographical morphing of azobenzene-doped liquid crystal polymer films via tunable photo-polymerization induced diffusion

Photo-polymerization is a convenient way to fabricate azobenzene-doped liquid crystal glassy polymeric networks. During the photo-polymerization process, monomer diffusion is initiated if mesogens with different reactivities are blended in the monomer mixture and the polymerization light intensity is not uniform. Upon the diffusion of liquid crystal monomers and azobenzenes, compositional inhomogeneities are introduced in the polymerized network, leading to stiffness and photo-responsivity gradients. However, the relation between this diffusion process, the resulting compositional gradients and the final light-triggered deformation is not well-understood. Here we developed a computational model to simulate the monomer diffusion and its effect on the mechanics of light-induced topographical switching. By demonstrating light-switchable folding motions and surface transformations of liquid crystal films with various molecular alignments, the photo-responsivity gradient is found to play a major role in modulating the switching performance. Furthermore, the photo-polymerization diffusion can be an effective approach to introduce spatially-varying material properties and to tailor the surface and film deformations by varying the wavelength, illumination area and polarization of the incoming light. The proposed framework can be used to evaluate and control photo-polymerization-induced monomer diffusion to tune light-triggered topographical morphing.