Low Molecular Weight Organic Materials Research Articles

MICRODISPLAY STRUCTURES BASED ON ORGANIC GREEN LIGHT EMITTING DIODES USING THERMALLY ACTIVATED DELAYED FLUORESCENCE MATERIALS

The aim of the work is to develop a new highly efficient light-emitting structure of microdisplays based on organic light-emitting diodes (OLED) for the modernization of the microdisplayes MDO 02 of the mass production. It is also intended to use the new OLED structure in subsequent developments of new series of microdisplays, including a green glow. Сomplete microdisplay element consists of а active matrix and OLED structure, which is a set of layers of low molecular weight organic materials. The active matrix of the microdisplay MDO 02 contains 800×3(RGB)×600 pixels for the full-color version and 800×600 pixels for the monochrome version. Microdisplay MDO 02 has the following characteristics: the nominal brightness of the full-color glow is 140 cd/m2, the monochrome glow is – 560 cd/m2, the unevenness of the brightness is not more than 15 %, the contrast in relative units is not less than 100:1, the power consumption is not more than 450 mW, the operating time on refusal not less than 5000 hours. To improve these characteristics, it is proposed to use OLED structure, including materials with thermally activated delayed fluorescence (TADF). Materials with TADF have a much simpler synthesis scheme, an expanded selection of starting components and do not need expensive rare and rare-earth metals, which are used for the synthesis of phosphorescent materials. A structure with high light (external quantum yield up to 26.2 %) and electrical parameters with the described dopant synthesis process was selected from a number of OLED structure. This structure consists of four organic layers: hole-injection, hole-transport, emission and electron-transport. As a dopant for the emission layer, material aICTRZs based on indocarbosol derivatives was used. The dopant aICTRZs was synthesized by us according to the proposed synthesis method. The characteristics of this structure were evaluated using an ITO / TAPC (30 nm) / TCTA (10 nm) / CBP (25 nm) / Bphen (30 nm) / LiF (0.5 nm) / Al (150 nm). Although the optical characteristics of such an LED did not reach the declared values, they showed quite good results. As a result, such an OLED structure can be used as an initial one and, with its further development, one can count on stable and high results of the optical and electrical characteristics of MDs.

Investigation of the Role That Bulk Electrolysis Conditions Play in the Evaluation of New Energy Storage Materials

The continued evolution and greening of the electric grid has spurred interest in redox flow batteries (RFBs) as scalable, flexible and potentially low cost energy storage devices1. Nonaqueous RFBs that utilize organic molecules for charge storage are an emerging concept which has garnered significant interest in the scientific community2. Of particular interest is the ability to tailor the molecular structure of the organic compounds to achieve desired properties such increased solubility, higher/lower redox potential and longer lifetimes3. However, because this is an infant field, while many candidate organic molecules have been reported, validations of performance and durability are inconsistent. Materials are evaluated under different conditions, including different charging rates, state-of-charge swings, reactant concentrations, and cell configurations3–5. This presents changes in terms of both comparative analysis (e.g., is material A better than material B?) and absolute metrics (e.g., what is the true stability of material A?). Here, we compare bulk electrolysis techniques, varying charging rates, concentrations, and cycling methods, to gain insight into how different testing protocols influence observed behavior. The overarching goal is to determine the most appropriate methods for quantifying cycle stability for new redox active materials and to provide guidance on best practices. References (1) Su, L.; Kowalski, J. A.; Carroll, K. J.; Brushett, F. R. Recent Developments and Trends in Redox Flow Batteries. In Rechargeable Batteries; Zhang, Z., Zhang, S. S., Eds.; Green Energy and Technology; Springer International Publishing, 2015; pp 673–712. (2) Kowalski, J. A.; Su, L.; Milshtein, J. D.; Brushett, F. R. Recent Advances in Molecular Engineering of Redox Active Organic Molecules for Nonaqueous Flow Batteries. Curr. Opin. Chem. Eng. 2016, 13, 45–52. (3) Sevov, C. S.; Brooner, R. E. M.; Chénard, E.; Assary, R. S.; Moore, J. S.; Rodríguez-López, J.; Sanford, M. S. Evolutionary Design of Low Molecular Weight Organic Anolyte Materials for Applications in Nonaqueous Redox Flow Batteries. J. Am. Chem. Soc. 2015, 137(45), 14465–14472. (4) Milshtein, J. D.; Kaur, A. P.; Casselman, M. D.; Kowalski, J. A.; Modekrutti, S.; Zhang, P. L.; Attanayake, N. H.; Elliott, C. F.; Parkin, S. R.; Risko, C.; Brushett, F. R.; Odom, S. A. High Current Density, Long Duration Cycling of Soluble Organic Active Species for Non-Aqueous Redox Flow Batteries. Energy Environ. Sci. 2016, 9(11), 3531–3543. (5) Huang, J.; Su, L.; Kowalski, J. A.; Barton, J. L.; Ferrandon, M.; Burrell, A. K.; Brushett, F. R.; Zhang, L. A Subtractive Approach to Molecular Engineering of Dimethoxybenzene-Based Redox Materials for Non-Aqueous Flow Batteries. J. Mater. Chem. A 2015, 3 (29), 14971–14976.

Evolutionary Design of Low Molecular Weight Organic Anolyte Materials for Applications in Nonaqueous Redox Flow Batteries

The integration of renewable energy sources into the electric grid requires low-cost energy storage systems that mediate the variable and intermittent flux of energy associated with most renewables. Nonaqueous redox-flow batteries have emerged as a promising technology for grid-scale energy storage applications. Because the cost of the system scales with mass, the electroactive materials must have a low equivalent weight (ideally 150 g/(mol·e(-)) or less), and must function with low molecular weight supporting electrolytes such as LiBF4. However, soluble anolyte materials that undergo reversible redox processes in the presence of Li-ion supports are rare. We report the evolutionary design of a series of pyridine-based anolyte materials that exhibit up to two reversible redox couples at low potentials in the presence of Li-ion supporting electrolytes. A combination of cyclic voltammetry of anolyte candidates and independent synthesis of their corresponding charged-states was performed to rapidly screen for the most promising candidates. Results of this workflow provided evidence for possible decomposition pathways of first-generation materials and guided synthetic modifications to improve the stability of anolyte materials under the targeted conditions. This iterative process led to the identification of a promising anolyte material, N-methyl 4-acetylpyridinium tetrafluoroborate. This compound is soluble in nonaqueous solvents, is prepared in a single synthetic step, has a low equivalent weight of 111 g/(mol·e(-)), and undergoes two reversible 1e(-) reductions in the presence of LiBF4 to form reduced products that are stable over days in solution.

Suppressing molecular aggregation in solution processed small molecule organic light emitting diodes

Solution processing of low-molecular weight organic materials for optoelectronic devices is a challenging task due to often strong molecular aggregation. We present a facile and universal route for suppressing the aggregation of molecules during wet-deposition of emission layers for organic light emitting diodes by incorporating electronically inactive polymers. Moderate polymer concentrations of about 10wt.% lead to only minor changes of the electrical performance while at the same time improving the film formation and consequently the device luminance significantly. The device performance matches the performance of vacuum processed devices with the same device architecture.

P.60: A Soluble Thermally‐Stable Organic Semiconductor Material for Field‐Effect Transistors

AbstractA novel solution‐processable low molecular weight organic semiconductor material TS‐5, which has high thermal stability and solubility with various aromatic solvents, was developed. Field effect transistors (FET) fabricated using TS‐5 as an active layer, exhibited p‐type transistor responses with mobilities greater than 1.0 cm2/Vs and are stable at 150°C in air condition.

Characterisation of transparent exopolymer particles (TEP) produced during algal bloom: a membrane treatment perspective

Algal blooms are currently a major concern of the membrane industry as it generates massive concentrations of organic matter (e.g. transparent exopolymer particles [TEP]), which can adversely affect the operation of membrane filtration systems. The goal of this study is to understand the production, composition and membrane rejection of these organic materials using different characterisation techniques. Two common species of bloom-forming freshwater and marine algae were cultivated in batch cultures for 30 days and the productions of TEP and other organic matter were monitored at different growth phases. TEP production of the marine diatom, Chaetoceros affinis, produced 6–9 times more TEP than the freshwater blue-green algae, Microcystis. The organic substances produced by both algal species were dominated by biopolymeric substances such as polysaccharides (45–64%) and proteins (2–17%) while the remaining fraction comprises of low molecular weight refractory (humic-like) and/or biogenic organic substances. MF/UF membranes mainly rejected the biopolymers but not the low molecular weight organic materials. MF membranes (0.1–0.4 μm) rejected 42–56% of biopolymers, while UF membranes (10–100 kDa) rejected 65–95% of these materials. Further analysis of rejected organic materials on the surface of the membranes revealed that polysaccharides and proteins are likely responsible for the fouling of MF/UF systems during an algal bloom situation.

Selective adsorption of dissolved organic matter to mineral soils

As soil solutions pass through forested mineral soils, the chemical and structural compositions of dissolved organic carbon (DOC) can alter substantially due to interactions with soil particle surfaces. Typically, adsorption processes dominate in mineral soils and the resulting concentration of DOC is reduced substantially. We studied changes in the molecular and structural compositions of DOC during equilibration with mineral soils collected across Canada (n=43) and found that the overall aromatic content of DOC decreased with equilibration in almost all cases from using specific absorbance (SUVA) and the fluorescence index. The fluorescence index revealed that podzolic B horizons, with typically large adsorption capacity (Qmax), had the greatest reduction in aromaticity, which was partially explained by the much lower aromatic content of DOC desorbed from soils surfaces. In contrast, a decrease in DOC aromaticity for volcanic B horizons, also with high Qmax, was primarily due to adsorption. An unexpected finding was the release of extremely high (2.6×106Da) and low (420Da) molecular weight (MW) organic materials during equilibration using high performance size exclusion chromatography (HPLC), for luvisols and podzols, respectively. In general, the average number–average MW (Mn) of DOC decreased for all soil types, but the greatest decrease in Mn was observed for mineral soils with large Qmax, including the podzolic and volcanic B horizons. Analysis of changes in FTIR spectra revealed that the most prominent change to DOC functional groups was a reduction in carboxyl groups, which was even greater than the removal of aromatic DOC. The findings of this study emphasize that while DOC concentrations may decrease substantially during passage through mineral soils, it is valuable to consider the contribution of DOC from desorption of pre-existing soil C. Essential to the findings of this study was the inclusion of multiple analytical techniques to track changes to DOC character, and the inclusion of a wide range of mineral soils.

Crystallization and Vitrification of a Cyanurate Trimer in Nanopores

The effects of nanopore confinement on the crystallization and vitrification of a low molecular weight organic material, tris(4-cumylphenol)-1,3,5-triazine, are investigated using differential scanning calorimetry. The material shows cold crystallization and subsequent melting in the bulk state. Under the nanoconfinement of controlled pore glasses (CPG), cold crystallization and melting shift to lower temperatures. Crystallization kinetics are hindered in nanoconfinement, and no crystallization occurs in 13 nm diameter pores over the course of a week. Using a traditional Avrami analysis, the restricted crystallization under nanopore confinement is quantified; for crystallization at 80 °C, the Avrami exponent decreases with decreasing pore size and the overall crystallization rate is approximately 30 times slower for material confined in 50 nm diameter pores than the bulk. When compared at the temperature at which the crystallization rate is a maximum, the Avrami exponent is higher in nanoconfined samples and the crystallization rate is approximately 10 times slower for material confined in 50 nm diameter pores. Under CPG nanoconfinement, the glass transition temperature also decreases and shows two values; interestingly, the T(g) values further decrease with increasing crystallinity.

Commercializing Biorefinery Technology: A Case for the Multi-Product Pathway to a Viable Biorefinery

While there may be many reasons why very interesting science ideas never reach commercial practice, one of the more prevalent is that the reaction or process, which is scientifically possible, cannot be made efficient enough to achieve economic viability. One pathway to economic viability for many business sectors is the multi-product portfolio. Research, development, and deployment of viable biorefinery technology must meld sound science with engineering and business economics. It is virtually axiomatic that increased value can be generated by isolating relatively pure substances from heterogeneous raw materials. Woody biomass is a heterogeneous raw material consisting of the major structural components, cellulose, lignin, and hemicelluloses, as well as minor components, such as extractives and ash. Cellulose is a linear homopolymer of D-glucopyrano-units with β-D(1®4) connections and is the wood component most resistant to chemical and biological degradation. Lignin is a macromolecule of phenylpropanoid units, second to cellulose in bio-resistance, and is the key component that is sought for removal from woody biomass in chemical pulping. Hemicelluloses are a collection of heteropolysaccharides, comprised mainly of 5- and 6-carbon sugars. Extractives, some of which have high commercial value, are a collection of low molecular weight organic and inorganic woody materials that can be removed, to some extent, under mild conditions. Applied Biorefinery Sciences, LLC (a private, New York, USA based company) is commercializing a value-optimization pathway (the ABS Process™) for generating a multi-product portfolio by isolating and recovering homogeneous substances from each of the above mentioned major and minor woody biomass components. The ABS Process™ incorporates the patent pending, core biorefinery technology, “hot water extraction”, as developed at the State University of New York College of Environmental Science and Forestry (SUNY-ESF). Hot water extraction in the absence of mineral acids and bases is preferred because of its ability to generate multiple high value output products without chemical input, recovery, or disposal costs. Instead of added chemicals in the cooking phase, the ABS Process™ relies upon an autocatalytic reaction in which acetyl groups, bound through an ester linkage to hemicellulose chains, are hydrolyzed at high temperature in water. The resulting acidic conditions (final pH ~3.5) and temperatures of 160–170 °C permit further solubilization and diffusion of oligomeric 5- and 6-carbon sugars, acetic acid, aromatic substances, monomeric sugars, and other trace compounds into the extract solution. These conditions also avoid extensive degradation of monosaccharides, enabling membrane fractionation and other chemical separation techniques to be used in the following separations. A range of separation techniques are applied on the extract solution to isolate and purify fermentable sugars, acetic acid, lignin, furfural, formic acid, other hemicellulose related compounds, lignin, lignin degradation products, and phenolic extractives for commercial sale. The extracted lignocellulosic biomass, with reduced hemicellulose content and is thus less heterogeneous, carries the value-added advantages of: (1) enhanced product characteristics, and (2) reduced energy and chemical manufacturing costs. Thus, by fractionating woody biomass into more homogeneous substances, the ABS Process™ holds potential as an economically viable pathway for capturing sustainable, renewable value not currently realized from lignocellulosic biomass.

Development and characterization of plasticized polyamides by fluid and solid plasticizers

Polyamides are semicrystalline polymers that are useful in a wide range of applications in the plastics industry. Some applications require higher flexibility and improved workability of polyamides; thus, a plasticization approach that eases compounding and processing procedures and produces better desired product properties can be utilized. Common plasticizers are high‐boiling liquid esters, but solid plasticizers also have been considered. The present research has focused on plasticization of nylon 66/6 (80/20) copolymer by using selected low molecular weight organic materials. Plasticization of the copolyamide was studied with glycerin mono stearate, benzene sulfonamide, and methyl 4‐hydroxybenzoate as the solid plasticizers and diethylhexyl phthalate as the liquid plasticizer. The materials were prepared and characterized by thermal, mechanical, dynamic, rheological, and morphological properties. The experimental results were supported by simulated polymer and plasticizer interactions using molecular dynamic simulations. Plasticization and antiplasticization phenomena were observed and discussed. The plasticizers were classified by their efficiency in reducing Tg and by modification of the other polyamide properties. Copyright © 2011 John Wiley & Sons, Ltd.

Development of naturally occurring siliceous material for the preferential removal of thorium from U–Th from aquatic environment

During this work highly particle reactive nature of thorium was exploited for the separation of Th from aquatic stream containing U/Th. The Kd value of Th(IV) ions is 106 which is two order of magnitude higher than uranium (IV & VI). Laboratory simulated experiments were conducted to study the preferential removal of thorium by using siliceous material having particle size of about 2,000 μm. Siliceous material was prepared by decomposing the organic layer on soil particles by giving treatment with HNO3 and H2O2. Experimental solutions were generated by spiking the surface water with Th (NO3)4 and UO2(NO3)2. Experimental results shows preferential uptake of Th compared to U by siliceous material. This association is further improved by coating the siliceous material with high and low molecular weight organic materials i.e. humic and fulvic acid, respectively. Characterization of the organic material was done by ATR–FTIR whereas determination of Th was done by ICP-OES and alpha spectrometry. Experimental results clearly showed that Th and U sorption capacity is 1 and 0.3 μg mg−1 (w/w), respectively, in case of siliceous material. Thorium sorption is increased five and eight times in the case of coating with fulvic acid and humic acid, respectively. Whereas the same does not shows any pronounced impact on sorption of uranium.

Study of visco-elastic properties of shoppers waste for its reuse as construction material

Plastic shoppers are made of low molecular weight organic materials. Due to throw away culture and non-decaying properties of shoppers, the waste has increased to alarming level since reuse or recycle industry is incompatible with the waste generation. The waste problems have attracted world-wide recognition and multiple solutions to tackle the problems are under consideration. There exists a great potential for reuse of shopper waste in construction industry. The waste has been used to fabricate compressed shoppers waste (CSW) blocks. This paper discusses the fabrication and testing of CSW-blocks as a construction material and determination of its visco-elastic properties. Based on properties, design charts have been developed for design of structural components using CSW-blocks as material. Application of design charts is also explained.

Molecular glass photoresists for advanced lithography

Molecular glass resists are low molecular-weight organic photoresist materials that readily form stable amorphous glasses above room temperature. We have created new families of molecular glass materials that function as both positive and negative resists capable of producing fine features as small as 35 nm line/space patterns using either extreme UV (13.4 nm) or electron beam lithography. These molecular glass resists have promising properties and are being considered as alternative choices to polymeric resists for next generation photoresist design.

Computer-Aided Chemistry Estimation Method of Electronic-Polarization Dielectric Constants for the Molecular Design of Low-k Materials

Using computer-aided chemistry, we attempted to develop an estimation method for screening potential low-k materials in ultra-large semiconductor integration (ULSI) device production research. Related to electronic polarizability of organic compounds and also polymers, dielectric constants were estimated without experimental data using the chemical structure of the material and computational chemistry programs such as Molecular Orbital Package (MOPAC) and Chem Draw. Initially, a method for calculating the density of low molecular weight organic materials was developed. Then, related to their electronic polarizability for these organic compounds, dielectric constants were calculated with good accuracy. This method was also expanded to one-dimensional polymeric materials and found to be a useful tool for the molecular design of new low-k materials in ULSI device production research.

Layer-by-Layer Self-Assembling of a Low Molecular Weight Organic Material by Different Electrostatic Adsorption Processes

A novel method has been reported to deposit low molecular weight organic materials by a layer-by-layer self-assembled film deposition method. A different electrostatic adsorption process has been followed to show its advantage over the conventional method. When an organic material, namely, alizarin violet, with fewer ionic groups was used as the anion for electrostatic self-assembly, the dye was found to come off the film during the subsequent polycation deposition. As an alternative approach, the dye has been anchored to the polycation via a physiabsorption process prior to deposition. By controlling the concentration ratio of the two, the combination of low molecular weight material and the polycation as a whole has been used as the polycation. The absorption spectra after each deposition showed that there was no material loss during layer depositions. The results showed that the method of anchoring low molecular weight molecules to polyions could effectively be used to deposit homogeneous layer-by-laye...

TRANSPARENT, ABRASION-RESISTANT COATINGS FOR METAL SUBSTRATES

Novel hybrid inorganic-organic network materials have been synthesized and applied as transparent abrasion-resistant coatings for metal substrates. A specially functionalized low molecular weight organic material (diethylenetriamine) served as a precursor for all coating formulations. Combination of this functionalized organic material with metal alkoxide(s) and other alkoxysilane functional materials in the sol–gel reaction led to hybrid inorganic–organic chemical networks. While still a liquid, the initiated coating formulations were applied to the desired metal substrates by a spin coating process followed by thermal curing. The substrates used in this study included aluminum, plain steel, conversion coated steel, stainless steel, copper, and brass. A fluorinated monomer has also been utilized in selected cases to tailor the surface-free energy of the coatings. Such coatings displayed a linear increase in the water contact angle with increasing mass fraction of fluorinated monomer in the formulation. Other formulations have been explored that contain an ultraviolet absorbing species. The effects of coating formulation, cu mperature, and cure time on abrasion resistance have been determined.

Microencapsulation of Uncharged Low Molecular Weight Organic Materials by Polyelectrolyte Multilayer Self-Assembly

Two uncharged microcrystalline substances, pyrene (PYR) and fluorescein diacetate (FDA), were rendered water dispersible by treatment with various amphiphilic substances and subsequently encapsulated by exposure to an alternating sequence of cationic and anionic polyelectrolytes. The amphiphilic compounds employed to charge the microcrystals were ionic surfactants, phospholipids, and polyelectrolytes with an amphiphilic nature. Polyelectrolyte layers were self-assembled onto the pre-charged microcrystalline templates by means of electrostatic layer-by-layer deposition, thus forming a multilayered polymeric shell around the crystalline cores. The semipermeable nature of the polymer multilayer shell was thereafter exploited to remove the templated core by exposure to a mild organic solvent. The release behavior of solubilized PYR and FDA from the crystalline core was examined by monitoring their fluorescence after dissolution with ethanol. Complete removal of the core yielded hollow polymer capsules of micr...

Vitrigens. I. Synthesis and Characterization of Low Molecular Weight Organic Glasses

New low molecular weight organic materials with a strong tendency towards glass formation and glass temperatures above room temperature were synthesized. These materials consist of twin molecules where two bulky groups, i.e. carbazole (Ca), 3,6-dibromocarbazole (DbrCa), 2,3-benzocarbazole (BC), 1,2-benzo-3,4-dihydrocarbazole (BCDH), phenothiazine (Ph), 1,8-naphthalic acid anhydride (NI), and pyrene-1-aldehyde (PY) have been linked by flexible or semi-flexible aliphatic or aromatic central units. Their structure-glass temperature relationship and some relations between thermodynamic parameters and amorphous properties are discussed.

Respiratory responses to inhaled small organic molecules and related agents encountered in the workplace.

Respiratory disease from inhalation of small organic molecules usually results from occupational exposure to these materials. Occupational lung diseases have been recognized for many centuries, but only recently have their pathogenesis and etiology begun to be elucidated. A major difficulty when defining the etiologic factors involved in respiratory diseases of occupational origin stems from the fact that onset of symptoms is frequently separated from the actual exposure to the agent(s) by a long latent period. Although research into this area is still in its infancy, great strides are being made that are leading to the identification of a number of causative agents and, in many cases, elucidation of the mechanisms involved. This information has aided the development of appropriate exposure standards, making the workplace a safer environment. Two main types of respiratory disease occur as a result of inhalation of low molecular weight organic material: asthma and hypersensitivity pneumonitis (also called extrinsic allergic alveolitis). It is our aim to discuss the clinical manifestations of these diseases and, using examples, to demonstrate methods of investigating both individuals and populations to determine the presence of the disease. Both organic vapors and particulates are capable of inducing respiratory disease; however, airborne particles must be respirable. In general, airborne particles exceeding 10~m diameter are filtered out in the upper respiratory tract. Smaller particles, however, are able to gain access to the trachea and larger bronchi, but, in general, only particles with a diameter of less than 5~m and greater than 0.5p, m can enter the alveoli and be retained in significant proportions. Smaller particles, althotjgh generally not retained in the lungs are still capable of causing respiratory disease. 1 The agents capable of causing respiratory disease include organic materials, such as animal and avian proteins, bacterial enzymes, chemical dusts and

Dissolved Organic Matter in Lakewater: Characteristics of Molecular Weight Size-Fractions and Ecological Implications

The dissolved organic matter pool in a soft-water lake was fractionated into six molecular weight components using ultramembrane filtration. A statistical relationship was found between organic carbon concentrations and molecular weight ranges within individual size-fractions. In characterizing these fractions, high (> 100000-50000) and low (2000-0) molecular weight organic materials were found to be labile (about 50 % decomposed in 4 h), following exposure to UV-light, while intermediate sized fractions (50000-2000) were essentially refractory. Chelation-complexation capacity for inorganic iron (59Fe) by high and low molecular weight fractions was increased significantly following exposure to UV-light. Bacterial 14C-labelled extracellular products were found to decompose at different rates in comparison to 12C organic compounds in individual molecular weight fractions, following exposure to UV-light, suggesting they were qualitatively different from one another.