High scratch and etch resistance by optimized cross-linking chemistry and density

Target of development in the field of modern automotive clear coats is the combination of high etch and high scratch resistance. For high etch resistance the cross-linking chemistry is the key factor. The property scratch resistance is mainly influenced by the cross-linking density and the flexibility of chains between netpoints. By combining these parameters high etch and scratch resistant clear coats can be formulated. As a representative example an optimized clear coat based on epoxy/acid cross-linking chemistry is discussed. The ways to achieve high cross-linking density are shown.     

Correlation of TLC,HPTLIC and PMD Results and Their Transfer to HPLC Systems

Abstract

The correlation of the results of five thin-layer chromatographic techniques and their transfer to high performance liquid chromatography are reported. The data obtained indicate that high performance thin-layer chromatographic results are faithfully reproduced by high performance liquid chromatography. Although plates were not activated, and mixed solvents were used, no major differences were observed between thin layer and high performance liquid chromatography.     

Synthesis and characterisation of branched polyarylethers

Polyarylethers (Polysulfone: PSU, Polyethersulfone: PES) belong to the group of high performance polymers, having high glass transition temperature as well as high continuous use temperature. As a consequence of their high glass transition temperature, these polymers display high melt viscosity, which limits the number of accessible applications. Since the conventional methods to improve the flow characteristics are limited, the influence of branching by incorporation of the tri-functional monomer 1,1,1-Tris-(4-hydroxyphenyl)ethane (THPE) on the flow and the mechanical performance of PES was studied. Branching enhances the flow of Polyethersulfone significantly, but has a deleterious effect on the toughness, especially Charpy impact and tensile elongation.     

Lipid lowering effects of high linoleate and high alpha-linolenate diets in rats and mice. Consequence of long-term feedings.

Diets high in linoleate (safflower oil) or high in alpha-linolenate (perilla oil) were fed to rats for 11 months, and the effects of the diets on plasma and tissue lipids were compared. The plasma levels of total cholesterol (Cho), phospholipids (PL) and triacylglycerol (TG) were significantly lower in the high alpha-linolenate group than in the high linoleate group, the differences being more than 30% in the levels of total Cho and TG. The diets had differential effects on the lipid contents of major tissues: the TG level in muscle was higher but both the TG level in depot fat and the PL level in muscle were lower in the high alpha-linolenate group than in the high linoleate group. In order to clarify whether or not the hypolipidemic effect of the high alpha-linolenate diet was due to changes in the distribution of lipids among tissues, whole body lipids were estimated in mice fed these diets for 5 months. The whole body Cho content was significantly lower, by 28%, in the high alpha-linolenate group compared with the high linoleate group, but the total lipid content, PL and neutral lipids were similar between the groups. Our results indicate that the high alpha-linolenate diet has a more potent cholesterol lowering effect in plasma and body tissue than the high linoleate diet; interestingly, whole body TG levels are similar but tissue distributions of TG are different between the two dietary groups.     

Highly enantioselective and regioselective nickel-catalyzed coupling of allenes, aldehydes, and silanes

A complex derived from Ni(cod)2 and NHC-IPr catalyzes a three-component coupling reaction involving allenes, aldehydes, and organosilanes and transfers the axial chirality of the allene to a stereogenic center in the product with very high fidelity. An unexpected regioselectivity is observed; favored are allylic rather than homoallylic alcohol derivatives, corresponding to the unusual process of coupling two electrophilic atoms: the allene sp and aldehyde carbon atoms. In all cases, high enantioselectivity, high Z/E selectivity, and, with differentially substituted allenes, high site selectivity are observed. This transformation represents the first enantioselective multicomponent coupling process of allenes.     

Purification and analysis of partially alkylated cyclodextrins by liquid and gas chromatography

Complex mixtures of partially alkylated cyclodextrins can be analyzed by both HPLC and high temperature capillary GC. Because of the limited efficiency of LC, suitable analytical and preparative separations can be achieved only with systems of carefully optimized selectivity. Using LC it has been possible to isolate and purify single cyclodextrin species from very complex mixtures of components which contain unreacted hydroxyl groups in addition to the alkoxy groups. Analysis of the reaction mixtures and of fractions taken from LC separations can be performed with advantage by high resolution capillary GC at high temperatures between 300 and 400 °C. The thermal stability of partially alkylated cyclodextrins in high temperature GC is considerably increased by trimethylsilylation of the free hydroxyl groups. Fast atom bombardment mass spectrometry and proton NMR were used to identify species isolated from the preparative LC separations.     

Crystallization and reinforcement of poly (vinylidene fluoride) nanocomposites: Role of high molecular weight resin and carbon nanotubes

The effect of high molecular weight resin and multi-walled carbon nanotubes (MWCNTs) on the crystallization, rheological and dynamic mechanical properties of poly (vinylidene fluoride) (PVDF) composites was investigated. A synergetic effect of the high molecular weight resin and MWCNTs on the nucleation in the crystallization process of the matrix has been observed, and their contributions to the crystallization of the matrix are two-sided. The composites containing both the high molecular weight resin and MWCNTs have much higher crystallization peak temperatures but lower crystallinity, especially for samples with high MWCNT content. For the isothermal crystallization at relative high temperatures, higher Avrami exponent and shorter half-time of crystallization are observed for the composites containing both the high molecular weight resin and MWCNTs. The introduction of the high molecular weight resin not only reinforces the matrix, but also promotes the dispersion of MWCNTs. The reinforcement and synergetic nucleation effects of the high molecular weight resin and MWCNTs were also confirmed by dynamic mechanical analysis.     

A Recyclable and Scalable High-Capacity Organic Battery

Redox organic electrode materials (OEMs) have attracted extensive attention for batteries due to the possibility to be designed with high performance. However, the practical application of OEMs requires rigor criteria such as low cost, recyclability, scalability and high performance etc. and hence seems still far away. Here, we demonstrate an OEM for high performance aqueous organic batteries. Quantification of the charge storage confirmed the storage of protons with fast reaction kinetics, thereby enabling the high performance at high mass loading. As a result, the laminated pouch cells delivered Ampere-hour-scale capacity with excellent cycling performance. Benefited from the small molecular nature and the stable both charged and discharged states, the electrodes can be recycled at any states of charge with high yields (more than 90 %). This work provides a substantial step in the practical applications of OEMs for the future sustainable batteries.     

Highly Conducting and Flexible Radical Crystals

Together with high conductivity, high flexibility is an important property required for next generation organic electronic components. Both properties are difficult to achieve together especially when the components are crystalline because of the intrinsic high brittleness of organic molecular crystals. We report an organic radical crystal system that has both high flexibility and high conductivity. The crystal consists of 9,10‐bis(phenylethynyl)anthracene radical cation ( BPEA^.+ ) units, and shows flexibility under pressure with high conductivity in ambient condition exhibiting average conductivity of 2.68 S cm^?1 when normal linear shape, as well as 2.43 S cm^?1 when bent. The structural analysis reveals that both a short π–π distance (3.290 Å) between BPEA^.+ units that are aligned along the crystal length direction, and the presence of PF₆^? counter ions induce flexibility and high electrical conductivity.     

Mixed-mode chromatography and its applications to biopolymers

Mixed-mode chromatography is a type of chromatography in which a chromatographic stationary phase interacts with solutes through more than one interaction mode. This technique has been growing rapidly because of its advantages over conventional chromatography, such as its high resolution, high selectivity, high sample loading, high speed, and the ability to replace two conventionally corresponding columns in certain circumstances. In this work, some aspects of the development of mixed-mode chromatography are reviewed, such as stationary phase preparation, combinations of various separation modes, separation mechanisms, typical applications to biopolymers and peptides, and future prospects.     

Optimizing Strength and Ductility of Titanium Alloys by Oxygen: Review and Prospect

The traditional strengthening elements of titanium alloys include Al, Mo, V, etc., however, the high cost and toxicity of these elements put a limit on their further applications for biomaterials. Ubiquitous light elements such as oxygen are hopeful replacement due to high biocompatibility. It is recognized that the oxygen enhances the strength but pays the price of brittleness, thus the amount of oxygen is constrained. However, recent study results indicated that excess oxygen can keep high ductility together with high strength of titanium. This paper reviews the influence and the mechanism of oxygen on the strength and ductility of titanium alloys, and provides a new perspective for the strengthening method of titanium alloys.     

3,5-Dinitrobenzoic acid catalyzed synthesis of 2,3-unsaturated O- and S-glycosides and tetrahydropyranylation of alcohols and phenols

A simple procedure for the synthesis of 2,3-unsaturated glycosides in acetonitrile and tetrahydropyranylation of alcohols and phenols in dichloromethane in the presence of 3,5-dinitrobenzoic acid is described. A variety of alcohols and thiols are reacted with glycals to give the desired products in high yields with high α-selectivity.     

Enantio- and diastereoselective catalytic alkylation reactions with aziridines

The first asymmetric phase transfer catalyzed alkylation reaction of a range of carbon acids with N-sulfonyl aziridines is reported. When 10 mol % of a cinchona derived quaternary ammonium salt was employed as the catalyst under mildly basic conditions, N-o-(trifluoromethane)benzenesulfonyl aziridine was efficiently ring-opened to afford the amino ethylene products in consistently high yields and high enantioselectivities (up to 97% ee). By employing substituted aziridines in single enantiomeric form, the corresponding enantiopure alkylation products could be obtained with a range of pronucleophiles in high yields and moderate to high diastereoselectivities (up to 30:1 dr).     

Azidoimidazolinium Salts: Safe and Efficient Diazo‐transfer Reagents and Unique Azido‐donors

2‐Azido‐1,3‐dimethylimidazolinium chloride (ADMC) and its corresponding hexafluorophosphate (ADMP) were found to be efficient diazo‐transfer reagents to various organic compounds. ADMC was prepared by the reaction of 2‐chloro‐1,3‐dimethylimidazolinium chloride (DMC) and sodium azide. ADMP was isolated as a crystal having good thermal stability and low explosibility. ADMC and ADMP reacted with 1,3‐dicarbonyl compounds under mild basic conditions to give 2‐diazo‐1,3‐dicarbonyl compounds in high yields, which were easily isolated in virtue of the high water solubility of the by‐products. ADMP showed high diazo‐transfer ability to primary amines even in the absence of metal salt such as Cu(II). Using this diazotization approach, various alkyl/aryl azides were directly obtained from their corresponding primary amines in high yields. Furthermore, naphthols reacted with ADMC to give the corresponding diazonaphthoquinones in good to high yields. In addition, 2‐azido‐1,3‐dimethylimidazolinium salts were employed as azide‐transfer and migratory amidation reagents.     

舰艇用LZN-2型高性能阻尼材料释放物定性定量分析与评价

舰艇舱室多为密闭环境,舱室内使用的非金属材料释放物是舱室污染的主要来源,因此对所选用的非金属材料必须进行常温释放物的定性定量分析。由于舰艇的特殊性,不仅要求非金属材料在常温条件下释放物的浓度符合舰艇舱室容许浓度,还要求材料在高温条件(火灾或爆炸)下不产生高毒性的物质。本文根据有关军用标准和规程对舰船用LZN-2型高性能阻尼材料常温释放物和高温热解物进行定性、定量分析,从而对其使用的安全性进行评估。     

尼群地平晶型转变条件及其影响因素的确定

根据熔化数据推算相变稳定性理论计算了尼群地平不同晶型之间的相变温度, 并分别考察了高温、高温和高湿及高压条件下的晶型转变. 理论推导尼群地平I与II, 尼群地平I与III, 尼群地平II与III的转化温度分别为158.88, 160.50和158.65 ℃, 三者均为单变关系, 且在高温条件下尼群地平II, III都转变为尼群地平I, 在高压条件下, II易转变为I. 试验结果表明室温下尼群地平I为稳定型, II和III为亚稳定型, 3种晶型稳定性顺序为尼群地平I＞II＞III.     

Application and utilization of chemoinformatics tools in lead generation and optimization

The process of Drug Discovery is a complex and high risk endeavor that requires focused attention on experimental hypotheses, the application of diverse sets of technologies and data to facilitate high quality decision-making. All is aimed at enhancing the quality of the chemical development candidate(s) through clinical evaluation and into the market. In support of the lead generation and optimization phases of this endeavor, high throughput technologies such as combinatorial/high throughput synthesis and high throughput and ultra-high throughput screening, have allowed the rapid analysis and generation of large number of compounds and data. Today, for every analog synthesized 100 or more data points can be collected and captured in various centralized databases. The analysis of thousands of compounds can very quickly become a daunting task. In this article we present the process we have developed for both analyzing and prioritizing large sets of data starting from diversity and focused uHTS in support of lead generation and secondary screens supporting lead optimization. We will describe how we use informatics and computational chemistry to focus our efforts on asking relevant questions about the desired attributes of a specific library, and subsequently in guiding the generation of more information-rich sets of analogs in support of both processes.     

The Highly Controlled and Efficient Polymerization of Ethylene

The highly controlled and efficient polymerization of ethylene is a very attractive but challenging target. Herein we report on a Coordinative Chain Transfer Polymerization catalyst, which combines a high degree of control and very high activity in ethylene oligo- or polymerization with extremely high chain transfer agent (triethylaluminum) to catalyst ratios (catalyst economy). Our Zr catalyst is long living and temperature stable. The chain length of the polyethylene products increases over time under constant ethylene feed or until a certain volume of ethylene is completely consumed to reach the expected molecular weight. Very high activities are observed if the catalyst elongates 60 000 or more alkyl chains and the polydispersity of the strictly linear polyethylene materials obtained are very low. The key for the combination of high control and efficiency seems to be a catalyst stabilized by only one strongly bound monoanionic N-ligand.     

Protein-resistant and fibrinolytic polyurethane surfaces

Surfaces with resistance to non-specific protein adsorption and a high capacity to bind plasminogen from plasma are developed for application as fibrinolytic surfaces in blood contact. A new method is reported for grafting poly(OEGMA-co-HEMA) copolymers on polyurethane surfaces. The OEGMA provides effective protein resistance due to the PEG side chains and the HEMA provides a high density of OH groups for attachment of lysine. Adsorption of fibrinogen from buffer and plasma to these surfaces is low, indicating significant protein resistance. Plasminogen binding from plasma is high, and clot dissolution on surfaces where plasminogen adsorbed from plasma is converted to plasmin is rapid.     

Efficient and versatile synthesis of star polymers in water and their use as emulsifiers

Core cross-linked star polymers of low polydispersity were efficiently prepared in high yield by RAFT-mediated emulsion and dispersion polymerizations in water at high solid content. These star polymers were demonstrated to be effective emulsifiers, and the emulsion was successfully used as template to fabricate polymer particles.