Cyclic Epoxy Research Articles

Lanthanide and Ladder-Structured Polysilsesquioxane Composites for Transparent Color Conversion Layers

Ladder-type polysilsesquioxanes (LPSQs) containing phenyl as a high refractive index unit and cyclic epoxy as a curable unit were found to be excellent candidates for a transparent color conversion layer for displays due to being miscible with organic solvents and amenable to transparent film formation. Therefore, the LPSQs were combined with luminescent lanthanide metals, europium Eu(III), and terbium Tb(III), to fabricate transparent films with various emission colors, including red, orange, yellow, and green. The high luminescence and transmittance properties of the LPSQs-lanthanide composite films after thermal curing were attributed to chelating properties of hydroxyl and polyether side chains of LPSQs to lanthanide ions, as well as a light sensitizing effect of phenyl side chains of the LPSQs. Furthermore, Fourier-transform infrared (FT-IR) and X-ray photoelectron spectroscopy and nanoindentation tests indicated that the addition of the nanoparticles to the LPSQs moderately enhanced the epoxy conversion rate and substantially improved the wear resistance, including hardness, adhesion, and insusceptibility to atmospheric corrosion in a saline environment. Thus, the achieved LPGSG-lanthanide hybrid organic-inorganic material could effectively serve as a color conversion layer for displays.

Structure Evolution of Graphitic Surface upon Oxidation: Insights by Scanning Tunneling Microscopy.

Oxidation of graphitic materials has been studied for more than a century to synthesize materials such as graphene oxide, nanoporous graphene, and to cut or unzip carbon nanotubes. However, the understanding of the early stages of oxidation is limited to theoretical studies, and experimental validation has been elusive. This is due to (i) challenging sample preparation for characterization because of the presence of highly mobile and reactive epoxy groups formed during oxidation, and (ii) gasification of the functional groups during imaging with atomic resolution, e.g., by transmission electron microscopy. Herein, we utilize a low-temperature scanning tunneling microscope (LT-STM) operating at 4 K to solve the structure of epoxy clusters form upon oxidation. Three distinct nanostructures corresponding to three stages of evolution of vacancy defects are found by quantitatively verifying the experimental data by the van der Waals density functional theory. The smallest cluster is a cyclic epoxy trimer. Their observation validates the theoretical prediction that epoxy trimers minimize the energy in the cyclic structure. The trimers grow into honeycomb superstructures to form larger clusters (1–3 nm). Vacancy defects evolve only in the larger clusters (2–3 nm) in the middle of the cluster, highlighting the role of lattice strain in the generation of vacancies. Semiquinone groups are also present and are assigned at the carbon edge in the vacancy defects. Upon heating to 800 °C, we observe cluster-free vacancy defects resulting from the loss of the entire epoxy population, indicating a reversible functionalization of epoxy groups.

Ladder-Structured Polysilsesquioxane/Al2O3 Nanocomposites for Transparent Wear-Resistant Windows

As a protective layer for deformable displays, we synthesized ladder-type polysilsesquioxanes (LPSQs) containing cyclic epoxy as a curable unit. The mechanical properties after photo- and thermal-curing of LPSQs with a small amount of added Al2O3 nanoparticles were compared with those of the pure LPSQs. The prepared LPSQ-Al2O3 nanocomposites and the pure LPSQs exhibited comparable optical transparencies and thermal stabilities. In addition, the degree of conversion of the applied epoxy units in LPSQs and the resulting mechanical properties, as monitored by Fourier transform infrared spectroscopy and nanoindentation tests, indicated that the addition of nanoparticles to LPSQs moderately enhanced the epoxy conversion rate and remarkably improved the wear resistance, including hardness, after photo-/thermal-curing processes. The LPSQ-Al2O3 nanocomposites achieved higher wear resistance than epoxy-silica nanocomposites containing similar curable functional groups and reinforcing fillers (silica). The excellent mechanical properties of the LPSQ-Al2O3 nanocomposites could be attributed to three-dimensionally interconnected networks of organic-inorganic hybrid-type chemical structures in the LPSQ as well as additional reinforcement from amine-functionalized Al2O3 nanoparticles covalently interconnected with the LPSQ. We believe that the devised LPSQ-Al2O3 nanocomposites could serve effectively as a wear-resistant platform for deformable display windows.

Cyclic-carbonate functionalized polymer brushes on polymeric microspheres: Immobilized laccase for degradation of endocrine disturbing compounds

A novel support material containing cyclic carbonate group for facile enzyme immobilization was synthesized from [poly(styrene-co-divinylbenzene)-graft-poly(glycidyl methacrylate)] “[PS-co-DVB-g-P(GMA)]” microsphere under carbon dioxide atmosphere. It was named as (poly(styrene-co-divinylbenzene)-graft-poly(cyclic-carbonate methacrylate)] “[PS-co-DVB-g-P(CCMA)]” microsphere. Laccase was covalently immobilized using the microspheres carrying cyclic epoxy and cyclic carbonate groups. The amount of enzyme loading on the cyclic carbonate groups of the microspheres was 47.8mg/g. The immobilized enzyme was used for degradation of Bisphenol A, and Congo Red dye in packed bed reactor. The immobilized laccase preserved its initial activity about 67.5% and 93.0% for degradation of Bisphenol A and Conge Red, respectively.

Construction of bicyclic systems containing an oxygen bridge by isomerization of cyclic epoxy alcohols

A novel method for constructing a 7-oxabicyclo[2.2.1]heptane skeleton was developed. The substrates, namely cis-3,4-epoxy-1-cyclohexanol derivatives, were prepared from the corresponding 3-cyclohexen-1-ol derivatives via a stereoselective epoxidation reaction using a vanadium catalyst. Upon heating with lithium iodide in propionitrile, the cis-epoxy alcohol was transformed into the 7-oxabicyclo[2.2.1]heptane derivative in high yield. The reaction proceeds through formation of a lithium alkoxide bearing an iodohydrin moiety, followed by an intramolecular SN2 reaction.

지환식 에폭시/표면개질된 마이크로-나노실리카 콤포지트의 유전특성

The surface of nanosilica and microsilica was modified in order to develop a high voltage insulation material for outdoor application. The modified silicas were well dispersed in an aliphatic cyclic epoxy resin. Dielectric properties were studied for 8 kinds of specimens: 1 kind of neat epoxy, 3 kinds of epoxy/microsilica composites, and 4 kinds of epoxy/microsilica/nanosilica composites. Complex dielectric constants were measured in the range of 10-2~1.2 Hz at room temperature.

Exploring the Ring-Opening Pathways in the Reaction of Morpholinyl Radicals with Oxygen Molecule

Quantum chemistry calculations using hybrid density functional theory and the coupled-cluster method have been performed to investigate the ring-opening pathways in the oxidation of morpholine (1-oxa-4-aza-cyclohexane). Hydrogen abstraction can form two different carbon-centered radicals, morpholin-2-yl or morpholin-3-yl, or the nitrogen-centered radical, morpholin-4-yl, none of which are found to have low-energy pathways to ring-opening. Extensive exploration of multiple reaction pathways following molecular oxygen addition to these three radicals revealed two competitive low energy pathways to ring-opening. Addition of O(2) to either carbon-centered radical, followed by a 1,4-H shifting mechanism can yield a long-lived cyclic epoxy intermediate, susceptible to ring-opening, following further radical attack. In particular, the second pathway begins with O(2) attack on morpholin-2-yl, followed by a 1,5-H shift and a unimolecular ring-opening without having to overcome a high barrier, releasing a significant amount of heat in the overall ring-opening reaction. The calculations provide valuable context for the development of mechanisms for the low temperature combustion chemistry of nitrogen and oxygen-containing fuels.

Highly Concentrated Catalytic Asymmetric Allylation of Ketones

[reaction: see text] We report the catalytic asymmetric allylation of ketones under highly concentrated reaction conditions with a catalyst generated from titanium tetraisopropoxide and BINOL (1:2 ratio) in the presence of isopropanol. This catalyst promotes the addition of tetraallylstannane to a variety of ketones to produce tertiary homoallylic alcohols in excellent yield (80-99%) with high enantioselectivities (79-95%). The resulting homoallylic alcohols can also be epoxidized in situ using tert-butyl hydroperoxide (TBHP) to afford cyclic epoxy alcohols in high yield (84-87%).

A computational study of the mechanism for the C6H5+CH2O reaction

The mechanism for the C6H5 + CH2O reaction has been investigated with hybrid density functional quantum-chemical and statistical theory calculations. The results reveal three possible reaction channels: (1) The abstraction reaction producing C6H6 + HCO; (2) addition to the C atom yielding C6H5CH2O and (3) addition to the O atom giving C6H5OCH2. The barriers for these 3 reactions, calculated at the B3LYP/aug-cc-pvtz level of theory using the geometry optimized with B3LYP/cc-pvdz are 0.8, 1.4 and 9.1 kcal mol−1, respectively. The C6H5CH2O radical can fragment to form C6H5CHO + H with a barrier of 19.4 kcal mol−1. It can also undergo isomerization reactions ia two cyclic epoxy intermediates to give C6H5OCH2 with a maximum barrier of 20.4 kcal mol−1. Transition-state theory calculations using the predicted energy barriers and structures for the rate constants of the abstraction reaction (1) lead to very good agreement with our recently measured values, while the result of RRKM calculations for the isomerization/decomposition of C6H5OCH2 to C6H5CHO + H also agrees quantitatively with available experimental data.

Cation-stabilizing auxiliaries in polyene cyclizations. 6. The fluorine atom as a cation-stabilizing auxiliary in biomimetic polyene cyclizations. 3. Use to effect regiospecific control

The fluorine atom substituted at the pro-C-13 position (steroid numbering) has been shown to be an effective cation-stabilizing (C-S) auxiliary in the acid-catalyzed cyclization of polyene substrates. The preparation of these polyenes employed the known fragmentation of cyclic epoxy hydrazones to construct the methylacetylenic and gem-dimethyl groups. The fluoroolefinic ketal Claisen and cyclopropylcarbinol rearrangements established the 3(E) and 11 (E) trisubstituted alkenes

ChemInform Abstract: Microbial Oxidation in Synthesis: Concise Preparation of (+)‐Conduritol F from Benzene.

AbstractThe cis‐cyclohexadienediol (I), prepared from benzene by microbial oxidation with Pseudomonas putida in a literature‐known manner, is esterified and then oxidized to give the cyclic epoxy carbonate (IV) which reacts with (R)‐(+)‐sec‐phenethyl alcohol (V), forming a 1:1‐mixture of the diastereomeric ethers (VI) and (VII).

Plastisol Sealants for Automotive Applications

Plastisol sealants are widely used in the automotive industry both as structural adhesives and as water-proofing compounds. Over the years, a variety of materials have been used to promote adhesion in formulated plastisol sealants. This paper covers experimental work with a series of plastisol sealants using silane coupling agents as integral blend adhesion promoters. Silanes with cyclic epoxy, mer capto, amino, and diamino functional groups have been studied. The influence of silane structure on adhesion, viscosity, viscosity stabil ity, flow properties, and sag resistance has been examined. After detailed study of formulating variables, it has been found that silane coupling agents will contribute significantly to the improvement of a number of essential sealant characteristics.