Polyimides from isomeric biphenyltetracarboxylic dianhydrides and the effects of chemical structure on solubility

A series of homopolyimides and copolyimides was synthesized by the solution condensation of biphenyltetracarboxylic dianhydride (BPDA) isomers and various diamines followed by chemical imidization. These polyimides had intermediate to high molecular weights with inherent viscosities of 0.34-1.01 dL/g for homopolyimides and 0.48-1.02 dL/g for copolyimides. Thermogravimetric analysis indicated that the aromatic polyimides were stable up to 500degreesC, and the 5% weight loss temperatures were recorded in the range of 506-597degreesC in an air atmosphere and in the range of 517-601degreesC in a nitrogen atmosphere, depending on the diamines used. The glass transition temperatures of aromatic homopolyimides were above 271degreesC, while the glass transition temperatures of the copolyimides increased with an increase in the 2, 2', 3, 3'-BPDA-component. The effects of the chemical structure of the polymer chain on the solubility were investigated. It was found that the solubility of BPDA-based polyimides could be improved by the introduction of flexible units, nonlinear and non-coplanar units, and copolymerization. The polyimides with nonlinear and non-coplanar units derived from 2, 2', 3, 3'-BPDA appeared to have prominently enhanced solubility in polar aprotic solvents and polychlorocarbons when compared with the homopolyimide derived from 3, 3', 4, 4'-BPDA.

Crystal structure and variation in unit cell parameters with crystallization temperatures of poly (ether ketone ether ketone ketone)s containing meta-phenyl links (PEKEKmK)

The X-ray diffraction patterns of the crystalline aromatic ketone polymer PEKEKmK (aryl ether ketone ether ketone ketone polymer containing meta-phenyl links) have been investigated (for the chemical structure, see Formula). An orthorhombic unit cell is proposed to contain two chains with a = 0.772 nm, b = 0.604 nm and c = 2.572 nm. According to the orthorhombic system, the 11 reflections of this polymer were indexed. Meanwhile, variation in unit cell parameters with crystallization temperatures of PEKEKmK was also investigated. [GRAPHICS]

Structure analysis of the fulvic acids extracted from composted corn stalk residue

Chemical structure of fulvic acids extracted from composted corn stalk residue(CSR FA)was studied by Fourier transform infrared (FTIR) spectroscopy, H-1 and C-13 nuclear magnetic resonance(H-1-NMR, C-13-NMR) spectroscopy. The results show that CSR FA mainly consists of four types of carbon: carbonyl, aromatical, alkyl and carbohydrate, the carbohydrate is dominant. Its aromaticity is 15.42%, less than that of CSR HA. This indicates that the construction of CSR FA is simpler than that of CSR HA, FA can not be extracted from undecomposed corn stalk residue. CSR FA may be formed by cellulose or hemicellulosemorties combined with aromatic compound from decomposed lignin.

Relationship between structure and gas permeation properties of polyimides prepared from oxydiphthalic dianhydride

Gas permeability coefficients of a series of aromatic polyimides, which were prepared from oxydiphthalic dianhydride (ODPA) with various aromatic diamines, with respect to H-2, CO2, O-2, N-2, and CH4 were measured under 10 atm and in the temperature range from 30 to 150 degrees C. A significant change in gas permeability and permselectivity resulting from systematic variation of the chemical structure of the polyimides was found. Among the polyimides which were prepared from phenylenediamine and its derivatives as well as bridged diamines without side groups on the benzene rings of the diamine residues, the increase of the gas permeability is accompanied by a decrease of the permselectivity. However, both the gas permeability and the permselectivity of the polyimides which were prepared from bridged diamines with methyl or methoxy groups on the benzene rings of the diamine residues simultaneously increase.

Structure/permeability and permselectivity relationship of polyetherimides from 1,4-bis(3,4-dicarboxyphenoxy) benzene dianhydride .2.

Gas permeability coefficients of a series of aromatic polyetherimides, which were prepared from 1,4-bis(3,4-dicarboxyphenoxy) benzene dianhydride (HQDPA) with various aromatic diamines, to H-2, O-2 and N-2 have been measured under 7 atm and at the temperature range 30-100 degrees C. A significant change in the permeability and permselectivity resulting from the systematic variation in chemical structure of the polyetherimides was found. Among the polyetherimides, that were prepared from phenylenediamine and methyl substituted phenylenediamines, the increase of permeability is accompanied by a decrease of permselectivity. The polyetherimides that were prepared from 3,5-diaminobenzoic esters have lower permselectivity than the others. However, the polyetherimide from 3,5-diaminobenzoic acid possesses much higher permselectivity than the others due to cross-linking. Copyright (C) 1996 Elsevier Science Ltd

Structure/permeability and permselectivity relationship of polyetherimides from 1,4-bis(3,4-dicarboxyphenoxy) benzene dianhydride .1.

Gas permeability coefficients of a series of aromatic polyetherimides, which were prepared from 1,4-bis(3,4-dicarboxyphenoxy) benzene dianhydride (HQDPA) and various aromatic diamines, to H-2, CO2, O-2, N-2 and CH4 have been measured under 7 atm pressure and over the temperature range 30-150 degrees C. A significant change in permeability and permselectivity, which resulted from a systematic variation in chemical structure of the polyetherimides, was found. Generally, increases in permeability of the polyetherimides are accompanied by decreases in permselectivity. The order of decrease of the permeability coefficients is as follows: HQDPA-IPDA > HQDPA-DDS > HQDPA-MDA > HQDPA-ODA > HQDPA-DABP > HQDPA-BZD. However, HQDPA-DMoBZD and HQDPA-DMoMDA, with bulky methoxy side-groups on the aromatic rings of the diamine residue, display both high permeability coefficients and high permselectivity. The favourable gas separation property, excellent thermal and chemical stability, and high mechanical strength make HQDPA-DMoBZD and HQDPA-DMoMDA promising candidates for membrane-based gas separation applications.

A SIMPLE METHOD FOR PREDICTION OF GAS-PERMEABILITY OF POLYMERS FROM THEIR MOLECULAR-STRUCTURE

A method for the prediction of gas permeabilities (P) through polymers from their chemical structure has been developed on the basis of the ratio of molar free volume to molar cohesive energy, V(f)/E(coh). The permeation of small gas molecules through polymer membranes is dependent on the chain packing density measured by V(f) and segmental motion of polymer chains measured by E(coh). But no simple relationship between P and V(f) or E(coh) alone was found. The permeability data of more than 60 polymers covering 7 orders of magnitude for six gases have been treated with linear regression analysis. All plots of log P vs. V(f)/E(coh) gave good straight lines. It is also found that a linear relationship holds when plotting both the intercepts and slopes of log P vs. V(f)/E(coh) lines against square of the diameters of gas molecules. Therefore, the permeabilities of all the non-swelling gases through a great variety of polymers can be estimated using two correlations above. Moreover, this method is more accurate than others in the literature and may found useful for the selection of gas separation or barrier membrane materials.

The structure of a sulfated galactan from Porphyra haitanensis and its in vivo antioxidant activity

The sulfated galactan fraction F1 isolated from the red seaweed, Porphyra haitanensis, showed typical porphyran structure. It has a linear backbone of alternating 3-linked beta-D-galactosyl units and 4-linked alpha-L-galactosyl 6-sulfate and 3,6-anhydro-alpha-L-galactosyl units. The L-residues are mainly composed of alpha-L-galactosyl 6-sulfate units, and the 3,6-anhydrogalactosyl units are minor. Partial methylation occurred at the C-6 position of the D-galactosyl units and at the C-2 position of the 3,6-anhydro-alpha-L-galactosyl units. Intraperitoneal administration of F1 significantly decreased the lipid peroxidation in aging mice. F1 treatment increased the total antioxidant capacity and the activity of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in aging mice. The results indicated that F1 had significant in vivo antioxidant activity. (C) 2003 Elsevier Ltd. All rights reserved.

Preparation and Tribological Studies of Stearic Acid Self-Assembled Monolayers on Polymer-Coated Silicon Surface

We present a good alternative method to improve the tribological properties of polymer films by chemisorbing a long-chain monolayer on the functional polymer surface. Thus, a novel self-assembled monolayer is successfully prepared on a silicon substrate coated with amino-group-containing polyethyleneimine (PEI) by the chemical adsorption of stearic acid (STA) molecules. The formation and structure of the STA-PEI film are characterized by means of contact-angle measurement and ellipsometric thickness measurement, and of Fourier transformation infrared spectrometric and atomic force microscopic analyses. The micro- and macro-tribological properties of the STA-PEI film are investigated on an atomic force microscope (AFM) and a unidirectional tribometer, respectively. It has been found that the STA monolayer about 2.1-nm thick is produced on the PEI coating by the chemical reaction between the amino groups in the PEI and the carboxyl group in the STA molecules to form a covalent amide bond in the presence of N,N'-dicyclohexylcarbodiimide (DCCD) as a dehydrating regent. By introducing the STA monolayer, the hydrophilic PEI polymer surface becomes hydrophobic with a water contact angle to be about 105degrees. Study of the time dependence of the film formation shows that the adsorption of PEI is fast, whereas at least 24 h is needed to generate the saturated STA monolayer. Whereas the PEI coating has relatively high adhesion, friction, and poor anti-wear ability, the STA-PEI film possesses good adhesive resistance and high load-carrying capacity and anti-wear ability, which could be attributed to the chemical structure of the STA-PEI thin film. It is assumed that the hydrogen bonds between the molecules of the STA-PEI film act to stabilize the film and can be restored after breaking during sliding. Thus, the self-assembled STA-PEI thin film might find promising application in the lubrication of micro-electromechanical systems (MEMS).

低极性化合物的电喷雾质谱检测方法及几种中藏药材的活性成分研究

本学位论文首先报道了为解决低极性化合物的电喷雾质谱（ESI-MS）分析难题而建立的一种衍生化分析方法；然后从色谱-质谱联用分析、分离纯化和结构鉴定等方面分别报道了几种中藏药材的活性成分研究。论文由下述六章组成： 第一章报道了盐酸羟胺衍生化方法在电喷雾质谱 (ESI-MS) 分析中的应用。该方法利用盐酸羟胺和羰基成肟的快速反应，建立了针对三萜酮等含酮或醛羰基低极性化合物的ESI-MS 信号增强技术。此方法不仅可应用于增强羰基化合物的ESI-MS 质谱信号，还可检测化合物中羰基的个数以及辨别涉及羰基官能团的同分异构体。此外，通过简单的氧化反应，还可将该方法拓展到三萜醇、甾醇等含羟基的低极性化合物，增强它们的ESI-MS 信号。对比已报道的相关ESI-MS 增强质谱信号的衍生化方法，此方法有经济、实用、快速和简便的显著特点。 第二章是关于野生羌活及其栽培品种化学成分的色谱-质谱联用分析。对不同产地野生羌活生长过程中活性成分的动态变化、野生羌活不同形态部位和人工栽培羌活中的活性成分含量进行了HPLC 定量分析。结果表明主要活性成分羌活醇和异欧前胡素都随生长期存在规律性变化，羌活不同形态部位中的活性成分含量也有明显不同。这些实验结果有些较好地印证了传统中医的用药理论，有些也对羌活的传统使用方法提出了新的建议。 第三章介绍了几种传统中藏药材的色谱-质谱联用及串联质谱分析。通过GC-MS 方法，从藏药材长花党参挥发油中共分离鉴定出45 个化合物；利用HPLC方法测定了该藏药材中的主要化学成分——木犀草素的含量（0.7%）；利用串联质谱技术，对西番莲和射干中的主要成分进行了快速鉴定，从西番莲中鉴定了4个黄酮碳苷；从不同产地的射干和川射干中鉴定了8 个主要异黄酮成分，其中包括一个未见报道的化合物。 第四章的内容为藏药材石莲叶点地梅的活性成分研究。从植物石莲叶点地梅(Androsace integra (Maxim.) Hand.-Mazz.) 乙醇提取物的正丁醇萃取部分共分离和鉴定了6 个化合物，利用MS 和NMR 等现代波谱学技术阐明了它们的结构：其中包括4 个三萜类化合物：分别是androsacin (1)、 ardisiacrispin A (2) 、saxifragifolin A (3) 和20(29)-lupen-3-one (4)；一个神经酰胺：4-羟基-Δ8,9(Z)-鞘氨醇-2'-羟基正二十四碳酸酰胺(5)；一个甾体类化合物：胡萝卜苷(6)。化合物1为新的13,28-epoxy-oleanane 型三萜皂苷，在其结构表征的过程中，采用LC-MS 进行糖分析，获得了值得推广的好结果。通过活性筛选发现化合物1~3 对HepG2肝癌细胞表现出不同程度的抑制活性，其中化合物2 活性最好，其IG50 为1.65μg/mL。 第五章是关于一些传统中藏药材的农药活性筛选。利用Syngenta 公司的活性筛选平台对68 种传统中藏药材醇提物进行了抗菌和除草的生物源农药活性筛选。结果表明所筛选的68 种植物提取物中，共有14 种样品表现出明显的除草/杀虫活性，其中水母雪莲花、松萝和茯神木等植物提取物还具有多种生物活性。活性成分还有待进一步追踪分离、纯化和结构鉴定。 第六章为文献综述，概述了羌活药材的研究进展。对羌活属及药用羌活植物从分类学、本草学、品质评价、人工栽培、化学成分及药理作用等方面进行了文献归纳和总结。 In this dissertation, an electrospray ionization mass spectrometry (ESI-MS) signal enhancement method, as well as the work of bioactive components study, HPLC-MS/MS application, bioassay screening, chromatograph separation and structure identification of the metabolites in several medicinal herbs have been reported. First chapter expounded a rapid, simple ESI-MS sensitivity enhancement method for detecting carbonyl groups in natural products has been developed by using hydroxylamine hydrochloride (NH2OH·HCl) as a derivatization reagent. We use the oxime formed during the derivatization reactions and its Beckmann rearrangement intermediates as a means of detecting the carbonyl groups originally present in these triterpenoids. In comparison with other derivatization methods in the literature, this method is simple, specific and can be used to detect carbonyl groups in triterpenoids which have low polarity and are poorly or non-ionizable. Moreover, it can also be used to detect hydroxyl groups by using the Dess-Martin periodinane (DMP) to convert primary and secondary hydroxyls into carbonyl groups. Chapter 2 reported an HPLC-MS method for analyzing the main bioactive compounds in both wild and cultured Notopterygium incisum. The results indicated that the main bioactive compounds varied through different seasons regularly, and in different commercial parts of this herb the content of these compounds also differed from each other. The quantitative analysis results showed that in the traditional commercial parts, the content of main chemical constitutes in Silkworm Notopterygium, Bamboo Notopterygium and Irregular-nodal Notopterygium are higher than that in Striped Notopterygium. This result is tally with the traditionally concept that the quality of Notopterygium, Bamboo Notopterygium and Irregular-nodal Notopterygium are better than that of Striped Notopterygium, which means that the quality of rhizomes is better than main roots. The chemical constituents of cultured N. incisum is reported for the first time in this dissertation and the analysis results showed some growth curves of chemical constituents in this plant, but still left some questions unanswered. Chapter 3 discussed the GC/LC-MS analysis of the traditional Chinese medicines Codonopsis thalictrifolis, Passiflora incarnate, Belamcanda chinensis and Passiflora incarnate. The main constituent, luteolin was isolated and identified from the traditional Tibet medicine of C. thalictrifolis. The quantitative analysis by HPLC has revealed that the content of luteolin in this herb is 0.7%. GC-MS was employed to analyzed chemical constituents of the essential oil from the flower of C. thalictrifolis. More than 60 peaks were detected and 45 of them were identified by comparing their spectra with that of the standards in the database and literatures. ESI-MS/MS was used to analyze the n-butanol extract of Passiflora incarnate. Based on the information of pseudo molecular ions and fragment ions of the glycosides, four major flavone-C-glycosides have been detected and identified as 7-methoxyluteolin-6-C-β-D-glucopyranoside, vitexin, swertisin and orientin. The isoflavone compounds in theextracts of three samples of B. chinensis collected in Gansu, Sichuan and Hunan, and the extract of Iris tectorum collected in Sichuan were analyzed by using TOF-HRMS and IT-MS. From the extracts of these herbs, a new isoflavone, identified as 5’,5,6,7-tetrahydroxy-3’4’-dimethoxyl isoflavon, and 7 known ones have been identified by analyzing the fragmentation patterns and their molecular formulas given by HRMS and the tandem mass spectrometry acquired by IT-MS. Chapter 4 elucidated the isolation and identification of a new triterpene saponin, androsacin (1), along with five known compounds (2-6) were isolated from the whole plants of Androsace integra (Maxim.) Hand.-Mazz., an herb used in traditional Chinese and Tibetan medicine. The chemical structure of the new compound was established as 3β-O-{β-D-glucopyranosyl-(1→4)-O-β-D-xylopyranosyl-(1→2)-O-β-D-glucopyranosyl-(1→4)-[O-β-D-glucopyranosyl-(1→2)]-α-L-arabinopyranosyl}-16α-hydroxy-13β,28-epoxy-olean-30-al by analyzing its MS, 1D- and 2D-NMR spectra. Compound 2 was cytotoxic toward HepG2 cancer cell with the GI50 value of 1.65 μg/mL. Chapter 5 described the biogenic pesticide activity screening of 68 traditional Chinese and Tibetan medicine extractions. The intention of this study is to explore bioactive natural compounds from these traditional medicinal herbs for biogenic insecticides use. Based on Syngenta’s bioassay, 14 extractions of these traditional medicines showed pesticide activities, and some of them had multi-activities on antibacterial and insecticidal. Chapter 6 is a review on the chemical and bioactivity research progress of Notopterygium incisum and N. forbesii.

The inhibitory effect of intestinal bacterial metabolite of ginsenosides on CYP3A activity

The intestinal bacterial metabolites of ginsenosides are responsible for the main pharmacological activities of ginseng. The purpose of this study was to find whether these metabolites influence hepatic metabolic enzymes and to predict the potential for ginseng-prescription drug interactions. Utilizing the probe reaction of CYP3A activity, testosterone 6beta-hydroxylation, the effects of derivatives of 20(S)-protopanaxadiol and 20(S)-protopanaxatriol families on CYP3A activity in rat liver microsomes were assayed. Our results showed that ginsenosides from the 20(S)-protopanaxadiol and 20(S)-protopanaxatriol family including Rb-1, Rb-2, Rc, Compound-K, Re, and Rg(1), had no inhibitory effect, whereas Rg(2), 20(S)-panaxatriol and 20(S)-protopanaxatriol exhibited competitive inhibitory activity against CVP3A activity in these microsomes with the inhibition constants (K) of 86.4+/-0.8mum, 1.7+/-0.1mum, and 3.2+/-0.2 mum, respectively. This finding demonstrates that differences in their chemical structure might influence the effects of ginsenosides on CYP3A activity and that ginseng-derived products might have potential for significant ginseng-drug interactions.

Preparation and characterization of microencapsulated hexadecane used for thermal energy storage

Polyurea microcapsules about 2.5 mum in diameter containing phase change material for thermal energy storage application were synthesized and characterized by interfacial polycondensation method with toluene-2,4-diisocyanate and ethylenediamine as monomers in an emulsion system. Hexadecane was used as a phase change material and OP, which is nonionic surfactant, and used as an emulsifier. The chemical structure and thermal behavior of the microcapsules were investigated by FTIR and thermal analysis respectively. The results show encapsulated hexadecane has a good potential as a solar energy storage material.

Polymeric fullerene oxide films produced by decomposition of hexanitro[60]fullerene

A new poly(fullerene oxide) thin film material has been fabricated by thermal activation and electron bombardment on hexanitro[60]fullerene (HNF) film deposited on a An substrate, all under vacuum conditions. The reaction products in the polymerization process are analyzed by XPS, UPS, IR, TGA-MS and LDI-MS techniques. It is found that the main effect of thermal and radiation treatments is to induce cleavage of -NO bonds from HNF molecules resulted in the release of nitric oxide gas and the formation of fullerene-bound oxyradicals, C-60-C-6. Spectroscopic evidence strongly suggests that rearrangement of fullerenic nitro moieties into nitrito groups is involved in the HNF decomposition process prior to the generation of reactive oxyradical intermediates. Consequently, the intermolecular coupling reaction of these oxyradicals leads to carbon polymer networks containing oxygen-bridged fullerenes. The thermally generated polymeric thin film is stable up to 900 K. Electron bombardment is also effective in both the decomposition of -NO2 groups and the removal of -OH groups present in HNF films. UV irradiation at 365 nm alone is shown to be not as efficient for the polymer formation. (C) 2003 Elsevier Ltd. All rights reserved.

Microencapsulation of n-hexadecane as a phase change material in polyurea

For thermal energy storage application, polyurea microcapsules about 2.5 mum in diameter containing phase change material were prepared using interfacial polycondensation method. In the system droplets in microns are first formed by emulsifying an organic phase consisting of a core material ( n-hexadecane) and an oil-soluble reactive monomer, toluene-2, 4-diisocyanate (TDI), in an aqueous phase. By adding water-soluble reactive monomer, diamine, monomers TDI and diamine react with each other at the interface of micelles to become a shell. Ethylenediamine (EDA), 1, 6-hexane diamine (HDA) and their mixture were employed as water-soluble reactive monomers. The effects of diamine type on chemical structure and thermal properties of the microcapsules were investigated by FT-IR and thermal analysis respectively. The infrared spectra indicate that polyurea microcapsules have been successfully synthesized; all the TG thermographs show microcapsules containing n-hexadecane can sustain high temperature about 300 degreesC without broken and the DSC measurements display that all samples possess a moderate heat of phase transition; thermal cyclic tests show that the encapsulated paraffin kept its energy storage capacity even after 50 cycles of operation. The results obtained from experiments show that the encapsulated n-hexadecane possesses a good potential as a thermal energy storage material.