Preparation and properties of soluble aromatic polyetherimides based on 2,2‐bis[4‐(3,4‐dicarboxyphenoxy)phenyl]hexafluoropropane dianhydride

Aromatic polyetherimides were synthesized from a fluorine containing aromatic carboxylic acid dianhydride, 2,2‐bis[4‐(3,4‐dicarboxyphenoxy)phenyl]hexafluoropropane dianhydride (6F‐BABPA) and five typical aromatic diamines including 1,1‐bis(4‐aminophenyl)‐1‐phenyl‐2,2,2‐trifluoroethane (3F‐DAM) by two‐step procedures—amidation to polyamic acids (PAA), followed by thermal imidization of PAA. The chemical and physical properties of the newly prepared polyetherimides (PEI) were compared in terms of their chemical structures, inherent viscosities, mechanical, and thermal properties. All polyetherimides were well soluble in common organic solvents such as N‐methyl‐2‐pyrolidone (NMP), N,N‐dimethylformamide (DMF), N,N‐dimethylacetamide (DMAc), pyridine, and methylene chloride. A PEI prepared from 6F‐BABPA/3F‐DAM was especially easily dissolved in NMP. The glass transition temperature (T_g) range of the obtained PEI was 209–257°C. The dielectric constants and refractive index were 2.8–3.2 and 1.61–1.56, respectively. The polyetherimide, 6F‐BABPA/BAPP, with a low fluorine content (11.4% fluorine content), has 0.99% water absorption, whereas the polyetherimide, 6F‐BABPA/4‐BDAP, having a high fluorine content (26.0% fluorine content) showed 0.35% of water absorption. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 249–257, 2000     

Synthesis and characterization of novel polyimides derived from 2,6-bis[4-(3,4-dicarboxyphenoxy)benzoyl]pyridine dianhydride and aromatic diamines

A novel pyridine-containing aromatic dianhydride monomer, 2,6-bis[4-(3,4-dicarboxyphenoxy)benzoyl]pyridine dianhydride, was synthesized from the nitro displacement of 4-nitrophthalonitrile by the phenoxide ion of 2,6-bis(4-hydroxybenzoyl)pyridine, followed by acidic hydrolysis of the intermediate tetranitrile and cyclodehydration of the resulting tetraacid. A series of new polyimides holding pyridine moieties in main chain were prepared from the resulting dianhydride monomer with various aromatic diamines via a conventional two-stage process, i.e. ring-opening polycondensation forming the poly(amic acid)s and further thermal or chemical imidization forming polyimides. The inherent viscosities of the resulting polyimides were in the range of 0.51-0.68 dL/g, and most of them were soluble in aprotic amide solvents and cresols, such as N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and m-cresol, etc. Meanwhile, some strong and flexible polyimide films were obtained, which have good thermal stability with the glass transition temperatures of 221-278 °C, the temperature at 5% weight loss of 512-540 °C, and the residue at 800 °C of 60.4-65.3% in nitrogen, as well as have outstanding mechanical properties with the tensile strengths of 72.8-104.4 MPa and elongations at breakage of 9.1-11.7%. The polyimides also were found to possess low dielectric constants.     

Synthesis and characterization of novel polyimides derived from 1,1-bis[4-(4′-aminophenoxy)phenyl]-1- [3″,5″-bis(trifluoromethyl)phenyl]-2,2,2-trifluoroethane

A novel fluorinated aromatic diamine monomer, 1,1-bis[4-(4′-aminophenoxy)phenyl]-1-[3″,5″-bis(trifluoromethyl)phenyl]-2,2,2-trifluoroethane(9FTPBA), was synthesized by coupling 3′,5′-bis(trifluoromethyl)-2,2,2-trifluoroacetophenone with 4-nitrophenyl phenyl ether under the catalysis of trifluoromethanesulfonic acid, followed reduced by reductive iron and hydrochloric acid. A series of new fluorine-containing polyimides having inherent viscosities of 0.96-1.23 dl/g was synthesized from the novel diamine with various commercially available aromatic dianhydrides using a standard two-stage process with thermal imidization and chemical imidization of poly(amic acid) films. All the fluorinated polyimides were soluble in many polar organic solvents such as NMP, DMAc, DMF, and m-cresol, as well as some of low boiling point organic solvents such as chloroform and acetone. The polymer films have good thermal stability with the glass transition temperature of 223-225 °C, the temperature at 5% weight loss of 535-568 °C in nitrogen, and have outstanding mechanical properties with the tensile strengths of 68-89 MPa, initial moduli of 2.14-2.19 GPa, and elongations at breakage of 3.2-10.5%.     

Syntheses and Properties of Aromatic Polyimides Based on 1,1-Bis[4-(4-aminophenoxy)phenyl]-1-phenyl-2,2,2-trifluoroethane and 1,1-Bis[4-(4-aminophenoxy)phenyl]-1-phenylethane

A series of fluorinated polyimides were prepared from 1,1-bis[4-(4-aminophenoxy)phenyl]-1-phenyl-2,2,2-trifluoroethane with various aromatic tetracarboxylic dianhydrides via a conventional two-step procedure. These polyimides were amorphous in nature and afforded flexible and tough films. Some polyimides derived from less stiff dianhydrides were soluble in polar organic solvents. The glass-transition temperatures (T _g) of these polyimides ranged from 252 to 324C, and softening temperatures (T _s) stayed in the 254322C range. Decomposition temperatures (T _d) at 10% weight loss all occurred above 569C in both air and nitrogen atmospheres. For a comparative study, another series of analogous polyimides based on 1,1-bis[4-(4-aminophenoxy)phenyl]-1-phenylethane were also pepared and characterized.     

Organosoluble, Low-Colored Fluorinated Polyimides Based on 1,1-Bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]-1-phenyl-2,2,2-trifluoroethane

A novel trifluoromethyl-substituted bis(ether amine) monomer, 1,1-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]-1-phenyl-2,2,2-trifluoroethane, was synthesized that led to a series of novel fluorinated polyimides via chemical imidization route when reacted with various commercially available aromatic tetracarboxylic dianhydrides. These polyimides were highly soluble in a variety of organic solvents such as N-methyl-2-pyrrolidone and N,N -dimethylacetamide, and most of them could afford transparent, low-colored, and tough films. These polyimides exhibited glass-transition temperatures (T _gs) of 227–269 °C and showed no significant decomposition below 500 °C under either nitrogen or air atmosphere. These polyimides had low dielectric constants of 2.87–3.17 at 10 kHz, low water uptake of 0.13%–0.58%, and an ultraviolet-visible absorption cutoff wavelength at 364–410 nm. For a comparative study, a series of analogous polyimides based on 1,1-bis[4-(4-aminophenoxy)phenyl]-1-phenyl-2,2,2-trifluoroethane were also prepared and characterized.     

Synthesis and properties of novel organosoluble polyimides derived from 1,4-bis[4-(3,4-dicarboxylphenoxy)]triptycene dianhydride and various aromatic diamines

A novel triptycene-based dianhydride, 1,4-bis[4-(3,4-dicarboxylphenoxy)]triptycene dianhydride, was prepared from 4-nitro-N-methylphthalimide and potassium phenolate of 1,4-dihydroxytriptycene (1). The aromatic nucleophilic substitution reaction between 4-nitro-N-methylphthalimide and 1 afforded triptycene-based bis(N-methylphthalimide) (2), which hydrolyzed and subsequently dehydrated to give the corresponding dianhydride (3). A series of new polyimides containing triptycene moieties were prepared from the dianhydride monomer (3) and various diamines in m-cresol via conventional one-step polycondensation method. Most of the resulting polyimides were soluble in common organic solvents, such as chloroform, THF, DMAc and DMSO. The polyimides exhibited excellent thermal and thermo-oxidative stabilities with the onset decomposition temperature and 10% weight loss temperature ranging from 448 to 486 °C and 526 to 565 °C in nitrogen atmosphere, respectively. The glass transition temperatures of the polyimides were in the range of 221-296 °C. The polyimide films were found to be transparent, flexible, and tough. The films had tensile strengths, elongations at break, and tensile moduli in the ranges 95-118 MPa, 5.3-16.2%, and 1.03-1.38 GPa, respectively. Wide-angle X-ray diffraction measurements revealed that these polyimides were amorphous.     

Gas separation properties of aromatic polyetherimides from 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride and 3,5-diaminobenzic acid or its esters

The gas transport properties of a series polyetherimides, which were prepared from 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride (HQDPA) with 1,3-phenylenediamine or 3,5-diaminobenzic acid (DBA) or its esters are reported. The effects of carboxylic group (—COOH) and carboxylic ether groups (—COOR), at five positions of 1,3-phenylenediamine moiety, on H₂ CO₂, O₂, and N₂ permeability, diffusivity, and solubility of the polyetherimides were investigated. The gas permeability, diffusion, and solubility coefficients of the polyetherimides containing COOR are bigger than those of HQDPA-PDA, but the ideal separation factors and ideal diffusivity selectivity factors are much smaller than that of HQDPA-PDA because COOR decreases chain segmental packing efficiency and increases chain segmental mobility. The permeability coefficients of HQDPA-DBA to H₂, CO₂, and O₂ are bigger than those of HQDPA-PDA; the ideal separation factors for gas pairs H₂/N₂, CO₂/N₂, and O₂/N₂ are also much bigger than those of HQDPA-PDA. Both the diffusion coefficients of CO₂ and O₂ and the ideal diffusivity selectivity factors for CO₂/N₂ and O₂/N₂ are bigger than those of HQDPA-PDA because COOH decreases both chain segmental packing efficiency and chain segmental mobility. The copolyimides, which were prepared from 3,5-diaminobenzic acid and 3,5-diaminobenzic esters, have both high permeability and high permselectivity. © 1997 John Wiley & Sons, Inc.     

Preparation and characterization of organosoluble polyimides based on 1,1-bis[4-(3,4-aminophenoxy)phenyl]cyclohexane and commercial aromatic dianhydrides

A bis(ether amine) III-A containing a cyclohexane cardo group, 1,1-bis[4-(4-aminophenoxy)phenyl]cyclohexane, was synthesized and used as a monomer to prepare polyimides VI-A with six commercial dianhydrides via three different procedures. The intermediate poly(amic acid)s had inherent viscosities of 0.83–1.69 dL g⁻¹ and were thermally or chemically converted into polyimides. Polyimides were also prepared by high-temperature direct polymerization in m-cresol and had inherent viscosities higher than the thermally or chemically cyclodehydrated ones. To improve the solubility of polyimides, six copolyimides were also synthesized from bis(ether amine) III-A with a pair of dianhydrides, which contained 3,3′,4,4′-diphenylsulfonetetracarboxylic dianhydride or 4,4′-hexafluoroisopropylidenediphthalic anhydride. Series VI-A polyimides were characterized by the good physical properties of their film-forming ability, thermal stability, and tensile properties. A comparative study of the properties, with the corresponding polyimides derived from 2,2-bis[4-(4-aminophenoxy)phenyl]propane, is also presented. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2750–2759, 2001     

Formation of honeycomb films based on a soluble polyimide synthesized from 2,2′‐bis[4‐(3,4‐dicarboxyphenoxy)phenyl]hexafluoropropane dianhydride and 3,3′‐dimethyl‐4,4′‐diaminodiphenylmethane

A soluble polyimide was synthesized from 2,2′‐bis[4‐(3,4‐dicarboxyphenoxy)phenyl]propane dianhydride (BPADA) and 3,3′‐dimethyl‐4,4′‐diaminodiphenylmethane (DMMDA) by a two‐step method, and it had good solubility both in strong bipolar solvents and in common low‐boiling‐point solvents. The BPADA–DMMDA polyimide was dissolved in chloroform (CHCl₃) and cast onto a glass substrate in a humid atmosphere. The BPADA–DMMDA/CHCl₃ solution easily formed honeycomb films. Some affecting factors, such as the polymer solution concentration, atmospheric humidity, and solvent volatility, were tested. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

2，2-双[4-（3，4-二氨基苯氧基）苯基]六氟丙烷的合成及表征

以六氟双酚A与5-氯-2-硝基苯胺为原料,在N,N-二甲基甲酰胺中发生缩合反应,再经Pd/C催化剂还原合成了一种新型的六氟四胺,其结构分别用元素分析、IR和 1HNMR进行了表征.这种新型四胺由于引入了六氟丙基和氧原子,可以用于合成溶解性能良好的聚苯并咪唑.     

Reactions of 4-[4′-(1′,3′-Diphenylpyrazolyl)methylene]-2-phenyl-5-oxo-2-oxazoline with grignard reagents and diazoalkanes

The title compound reacts with two moles of Grignard reagents with 1,2-addition to give the alcohol 4 , and/or the oxazoline 5 , or with 1,4-addition to give the amino ketone 6 . A reaction mechanism is proposed. Diazomethane is always added to the exocyclic double bond in 1 , but diphenyldiazomethane, in addition, replaces the carbonyl-oxygen by a benzhydrylidene group to give compound 9 .     

Adhesion property of novel polyimides with 1‐[3′,5′‐bis(trifluoromethyl)phenyl] pyromellitic dianhydride

Novel polyimides were synthesized from 1‐[3′,5′‐bis(trifluoromethyl)phenyl] pyromellitic dianhydride (6FPPMDA) by a conventional two‐step process: the preparation of poly(amic acid) followed by solution imidization via refluxing in p‐chlorophenol. The diamines used for polyimide synthesis included bis(3‐aminophenyl)‐3,5‐bis(trifluoromethyl)phenyl phosphine oxide, bis(3‐aminophenyl)‐4‐trifluoromethylphenyl phosphine oxide, and bis(3‐aminophenyl)phenyl phosphine oxide. The synthesized polyimides were designed to have a molecular weight of 20,000 g/mol by off‐stoichiometry and were characterized by Fourier transform infrared, NMR, differential scanning calorimetry, and thermogravimetric analysis. In addition, their intrinsic viscosity, solubility, water absorption, and coefficient of thermal expansion (CTE) were also measured. The adhesion properties of the polyimides were evaluated via a T‐peel test with bare and silane/Cr‐coated Cu foils, and the failure surfaces were investigated with scanning electron microscopy. The 6FPPMDA‐based polyimides exhibited high glass‐transition temperatures (280–299°C), good thermal stability (>530°C in air), low water absorption (1.46–2.16 wt %), and fairly low CTEs (32–40 ppm/°C), in addition to good adhesion properties (83–88 g/mm) with silane/Cr‐coated Cu foils. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1801–1809, 2005     

Synthesis and properties of organosoluble polyimides based on 1,1-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]cyclohexane

New aromatic diamine with cyclohexane cardo group substituted with trifluoromethyl group in the side chain, 1,1-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]cyclohexane (II), was prepared through the nucleophilic substitution reaction of 1,1-bis(4-hydroxyphenyl)cyclohexane and 2-chloro-5-nitrobenzotrifluoride in the presence of potassium carbonate, to yield the intermediate dinitro compound I, followed by catalytic reduction with hydrazine and Pd/C to afford the diamine II. Fluorinated polyimides (IVa-g) were prepared from the II with various aromatic dianhydrides via thermal or chemical imidization of poly(amic acid). These polyimides had inherent viscosity ranging from 0.72 to 1.16 dl/g and showed excellent solubility in a variety of organic solvents. They were soluble in a concentration of 10% in the amide polar solvent, and 1-5% in the other testing solvents. IV films showed good mechanical properties, excellent thermal stability. The 10% weight loss temperature was above 476 °C in nitrogen or air, and the glass transition temperature was recorded at 214-278 °C. In comparison of the IV series with the analogous nonfluorinated polyimides (V series) based on 1,1-bis[4-(4-aminophenoxy)phenyl]cyclohexane (II′), IV series revealed better solubility, lighter-colored and lower dielectric constants and moisture absorptions. Their films had cut-off wavelengths in the range of 364-414 nm, b^* value (a yellowness index) ranging from 3.3 to 66.3, dielectric constants of 3.02-3.55 (1 MHz), with moisture absorption of 0.16-0.36 wt%.     

Synthesis and characterization of novel fluorinated polyimides derived from 4,4′-[2,2,2-trifluoro-1-(3,5-ditrifluoromethylphenyl)ethylidene]diphthalic anhydride and aromatic diamines

A novel fluorinated aromatic dianhydride, 4,4′-[2,2,2-trifluoro-1-(3,5-ditrifluoromethylphenyl) ethylidene] diphthalic anhydride (9FDA), was synthesized, which was employed to polycondense with various aromatic diamines, including 4,4′-oxydianiline, 1,4-bis(4-aminophenoxy) benzene, 3,4′-oxydianiline and 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene to produce a series of fluorinated aromatic polyimides. The fluorinated polyimides obtained had inherent viscosities ranged of 0.61-1.14 dL/g and were easily dissolved both in polar aprotic solvents and in low boiling point common solvents. High quality polyimide films could be prepared by casting the polyimide solution on glass plate followed by thermal baking to remove the organic solvents and volatile completely. Experimental results indicated that the fluorinated polyimides exhibited good thermal stability with glass transition temperature ranged of 245-283 °C and temperature at 5% weight loss of 536-546 °C. Moreover, the polyimide films showed outstanding mechanical properties with the tensile strengths of 87.7-102.7 MPa and elongation at breaks of 5.0-7.8%, good dielectric properties with low dielectric constants of 2.71-2.97 and low dissipation factor in the range of 0.0013-0.0028.     

Synthesis and characterization of novel aromatic poly(amide‐imide)s derived from 2,2′‐bis(4‐trimellitimidophenoxy)biphenyl or 2,2′‐bis(4‐trimellitimidophenoxy)‐1,1′‐binaphthyl and various aromatic diamines

New aromatic diimide‐dicarboxylic acids having kinked and cranked structures, 2,2′‐bis(4‐trimellitimidophenoxy)biphenyl (2a) and 2,2′‐bis(4‐trimellitimidophenoxy)‐1,1′‐binaphthyl (2b), were synthesized by the reaction of trimellitic anhydride with 2,2′‐bis(4‐aminophenoxy)biphenyl (1a) and 2,2′‐bis(4‐aminophenoxy)‐1,1′‐binaphthyl (1b), respectively. Compounds 2a and 2b were characterized by FT‐IR and NMR spectroscopy and elemental analyses. Then, a series of novel aromatic poly(amide‐imide)s were prepared by the phosphorylation polycondensation of the synthesized monomers with various aromatic diamines. Owing to structural similarity, and a comparison of the characterization data, a model compound was synthesized by the reaction of 2b with aniline. The resulting polymers with inherent viscosities of 0.58–0.97 dl g^?1 were obtained in high yield. The polymers were fully characterized by FT‐IR and NMR spectroscopy. The ultraviolet λ_max values of the poly(amide‐imide)s were also determined. The polymers were readily soluble in polar aprotic solvents. They exhibited excellent thermal stabilities and had 10% weight loss at temperatures above 500 °C under a nitrogen atmosphere. Copyright © 2003 Society of Chemical Industry     

Synthesis and properties of novel aromatic polyamides derived from 2,2‐bis[4‐(4‐amino‐2‐fluorophenoxy) phenyl]hexafluoropropane and aromatic dicarboxylic acids

A series of polyamides were synthesized by the direct polycondensation of 2,2‐bis[4‐(4‐amino‐2‐fluorophenoxy)phenyl]hexafluoropropane with various commercially available dicarboxylic acids such as terephthalic acid, isophthalic acid, 5‐t‐butyl isophthalic acid, and 2,6‐naphthalene dicarboxylic acid. The synthesized polyamides were soluble in several organic solvents such as N,N‐dimethylformamide, N,N‐dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran, and chloroform, and they exhibited inherent viscosities of 0.42–0.59 dL/g. The polyamides exhibited weight‐average molecular weights of up to 26,000, which depended on the exact repeating unit structure. These polyamides showed good thermal stability up to 440°C for a 10% weight loss in synthetic air. The polyamides synthesized from 5‐t‐butyl isophthalic acid and isophthalic acid exhibited glass‐transition temperatures of 217 and 185°C, respectively (by differential scanning calorimetry) in nitrogen. The polyamides synthesized from terephthalic acid and 2,6‐naphthalene dicarboxylic acid showed melting temperatures of 319 and 385°C, respectively. The polyamides films were pale yellow, with tensile strengths of up to 82 MPa, moduli of elasticity of up to 2.3 GPa, and elongations at break of up to 9%, which depended on the exact repeating unit structure. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 691–696, 2003     

Novel soluble polyimides derived from 2,2′-bis[4-(5-amino-2-pyridinoxy)phenyl]hexafluoropropane: Preparation,characterization, and optical,dielectric properties

Two novel aromatic diamine monomer, 2,2′-bis[4-(5-amino-2-pyridinoxy)phenyl] hexafluoropropane (6FBAPDP) and 2,2′-bis[4-(5-amino-2-pyridinoxy)phenyl] propane (BAPDP), were successfully synthesized. Aimed at clarifying the structure-property relationships of pyridine-containing high-performance polymers, a series of novel fluorinated polyimides PI-(1–4) were prepared from 6FBAPDP with various commercially aromatic anhydrides, and polyimide (PI-5) was synthesized derived from BAPDP and 2,2′-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) via a two-stage process with heating imidization method. The fluorinated polyimides PI-(1–4) exhibited good solubility in strong polar solvents, such as N, N-dimethylacetamide, N, N-dimethylformamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, m-cresol, and could afford flexible, tough and transparent films with an UV–visible absorption cut-off wavelength at 342–393 nm. The glass transition temperatures of these polyimides were recorded between 239 and 306 °C by differential scanning calorimetry, and the 5% weight loss occurred at temperatures above 498 and 490 °C, in nitrogen and air, respectively. The polyimide films had the in-plane coefficients of thermal expansion (CTE) that ranged from 54 to 74 ppm °C⁻¹. Moreover, the fluorinated polyimide films showed low moisture absorptions of 0.51–0.82% and outstanding mechanical properties with the tensile strengths of 75–100 MPa, tensile moduli of 3.2–4.0 GPa and elongation at break of 5.5–10.3%, good dielectric properties with low dielectric constants of 2.71–2.92 at 1 MHz.     

Preparation of novel copoly(bis[4‐(3‐aminophenoxy)phenyl]sulfone/ 3,3′,4,4′‐benzophenonetetracarboxyl/ pyromellite)imide derivatives

Copolyimide derivatives were prepared from two carboxylic dianhydrides [3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA) and pyromellitic anhydride (PMDA)] and a single diamine (bis[4‐(3‐aminophenoxy)phenyl]sulfone [BAPS]) following one‐step polymerization. Copolymers could be arranged in sequence through different molar ratios of dianhydride compounds. These polymers were characterized by viscosity, thermal and mechanical properties, solubility, etc. To understand the behavior of the properties, according to the ratio of the dianhydride compound, a copolymer having various properties could be obtained. Further, it was proved that their properties could be determined from the compositions. The solubility of copolyimides with a large molecular weight was moderately improved. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 853–859, 2003     

Synthesis and properties of new aromatic polyimides based on 2,2′‐dibromo‐4,4′,5,5′‐benzophenone tetracarboxylic dianhydride

New polyimides with enhanced thermal stability and high solubility were synthesized in common organic solvents from a new dianhydride, 2,2′‐dibromo‐4,4′,5,5′‐benzophenone tetracarboxylic dianhydride (DBBTDA). DBBTDA was used as monomer to synthesize polyimides by using various aromatic diamines. The polymers were characterized by IR and NMR spectroscopy and elemental analysis. These polyimides had good inherent viscosities in N‐methyl‐2‐pyrrolidinone (NMP) and also high solubility and excellent thermo‐oxidative stability, with 5 % weight loss in the range 433 to 597 °C. Copyright © 2004 Society of Chemical Industry