Michael Day

Bio: Michael Day is an academic researcher from National Research Council. The author has contributed to research in topics: Arylene & Ether. The author has an hindex of 26, co-authored 51 publications receiving 2074 citations.

Synthesis and properties of random and alternating fluorene/carbazole copolymers for use in blue light-emitting devices

Abstract: Random and alternating fluorene/carbazole (F/Cz) copolymers with various carbazole contents (20−50 mol %) have been designed and synthesized for use as the hole-transporting as well as light-emitting layer in blue light-emitting diodes (LEDs). DSC analysis has indicated the complete suppression of the crystallizability of these polymers by the introduction of 3,6-carbazole linkages into the polymer backbone, which also results in changes in their optical properties. The absorption maximum has been blue-shifted with an increase in the carbazole content due to the interruption in the main chain conjugation. Meanwhile, the photoluminescent properties have been influenced by the sequence distribution of the fluorene segments as well as the carbazole content. The emission maxima and vibronic features of the alternating copolymers have changed with carbazole content, reflecting the differences in the electronic structures of the repeat units. However, in the case of the random copolymers, the emission spectra r...

Synthesis and Characterization of Alternating Copolymers of Fluorene and Oxadiazole

Abstract: Alternating copolymers of 9,9-dioctylfluorene and oxadiazole have been prepared by the tetrazole route or the Suzuki coupling reaction. In the polymers the oxadiazole units were evenly dispersed in the main chain at every one, P(F1-alt-Ox), three, P(F3-alt-Ox), or four, P(F4-alt-Ox), fluorene units. Another copolymer with an asymmetric repeat unit structure, P(F3−Ox−F1−Ox) has also been prepared for comparison. In this study, the tetrazole route has been demonstrated to offer several advantages for preparing polyoxadiazole with well-defined structures compared to other oxadiazole ring formation reactions. These advantages include: clean and fast reactions, mild reaction conditions, high yields, and high molecular masses of product. The glass transition temperature of copolymers ranged from 98 to 150 °C, and the copolymers show high thermal stability with decomposition temperatures around 430 °C. The UV−vis absorption and photoluminescence properties of all the copolymers in solutions are similar to those...

Photochemical degradation of poly(ethylene terephthalate). III. Determination of decomposition products and reaction mechanism

Abstract: The vacuum photolysis and air photo-oxidation of poly(ethylene terephthalate) were studied using light in the wavelength ranges of 225–420 nm and 300–420 nm. The volatile photodegradation products were determined by mass-spectrometric and gas-chromatographic analysis; CO and CO2 were found to be the predominant products. In addition, the rates of formation of carboxylic acid endgroups and the net weight losses of the film samples were determined as a function of irradiation time. Quantum yields for the initial rates of formation of CO and CO2 and of COOH within the film were calculated. On the basis of the results obtained, in this and the preceding papers in this series, reaction mechanisms have been proposed for the photochemical degradation of the polymer. The production of CO and COOH in both vacuum and air have been attributed mainly to a Norrish type I cleavage and a Norrish type II photorearrangement, respectively. It has also been concluded that, in the presence of air, an oxidative reaction sequence occurs whereby alkyl radicals produced on photolysis react with oxygen to form ROO. radicals. These subsequently react further to produce CO2 as the main volatile product of photooxidation.

Pure Deep Blue Light-Emitting Diodes from Alternating Fluorene/Carbazole Copolymers by Using Suitable Hole-Blocking Materials

Abstract: The influences of the carbazole content on the photophysical, electrochemical, and electroluminescent properties of alternating fluorene/carbazole copolymers PFnCz (n = 1, 2, 3) with well-defined c...

Photochemical degradation of poly(ethylene terephthalate). II. Effect of wavelength and environment on the decomposition process

Abstract: Poly(ethylene terephthalate) has been irradiated with UV light of different wavelengths and in various atmospheres. The extent of degradation was monitored by measuring the tensile strength, molecular weight, carboxylic acid endgroups, and fluorescence emission of the polymer. The importance of wavelengths <315 nm in causing deterioration was demonstrated to be mainly due to strong surface absorption which results in surface crazing and ultimate fracture under stress. Irradiation in nitrogen and under vacuum were found to give similar results, but with oxygen present in the system several significant differences were observed. In nonoxidative irradiations, crosslinking and discoloration of the polymer occurred. Under oxidative conditions, chain scissions and fluorescent material build-up resulted, whereas no crosslinking and only slight discoloration was observed. The possibility of a photo-oxidation reaction has thus been suggested, involving hydroperoxide formation, to explain the discrepancy in results obtained for the two types of environments.

Synthesis of Light-Emitting Conjugated Polymers for Applications in Electroluminescent Devices

Abstract: A review was presented to demonstrate a historical description of the synthesis of light-emitting conjugated polymers for applications in electroluminescent devices. Electroluminescence (EL) was first reported in poly(para-phenylene vinylene) (PPV) in 1990 and researchers continued to make significant efforts to develop conjugated materials as the active units in light-emitting devices (LED) to be used in display applications. Conjugated oligomers were used as luminescent materials and as models for conjugated polymers in the review. Oligomers were used to demonstrate a structure and property relationship to determine a key polymer property or to demonstrate a technique that was to be applied to polymers. The review focused on demonstrating the way polymer structures were made and the way their properties were controlled by intelligent and rational and synthetic design.

Recent advances in molecular imprinting technology: current status, challenges and highlighted applications

Abstract: Molecular imprinting technology (MIT) concerns formation of selective sites in a polymer matrix with the memory of a template. Recently, molecularly imprinted polymers (MIPs) have aroused extensive attention and been widely applied in many fields, such as solid-phase extraction, chemical sensors and artificial antibodies owing to their desired selectivity, physical robustness, thermal stability, as well as low cost and easy preparation. With the rapid development of MIT as a research hotspot, it faces a number of challenges, involving biological macromolecule imprinting, heterogeneous binding sites, template leakage, incompatibility with aqueous media, low binding capacity and slow mass transfer, which restricts its applications in various aspects. This critical review briefly reviews the current status of MIT, particular emphasis on significant progresses of novel imprinting methods, some challenges and effective strategies for MIT, and highlighted applications of MIPs. Finally, some significant attempts in further developing MIT are also proposed (236 references).

Degradation Rates of Plastics in the Environment

Abstract: Plastic waste is currently generated at a rate approaching 400 Mt year–1. The amount of plastics accumulating in the environment is growing rapidly, yet our understanding of its persistence is very...

Advances in the Synthesis of Organoborane Polymers for Optical, Electronic, and Sensory Applications

Abstract: The past decade has witnessed renewed interest and numerous unexpected discoveries in the area of main group organometallic chemistry. Unusual bonding modes have been uncovered,1-4 new materials have been developed,5,6 and new applications are being pursued.7-12 With respect to new materials with unusual properties, an exciting field is the development of hybrid polymers that combine main group elements with typical organic structures in one framework.13,14 Among main group organic-inorganic hybrid polymers, those involving Group 14 and Group 15 elements have received tremendous attention over the past several decades, with silicones, polysilanes, and polyphosphazenes among the most thoroughly studied materials.15-17 A variety of other classes of new polymers containing not only silicon and phosphorus,18-22 but also the heavier homologues, such as germanium, tin, arsenic, and antimony have been introduced more recently.23-26