Gas‐transport properties of indan‐containing polyimides

A series of indan‐containing polyimides were synthesized, and their gas‐permeation behavior was characterized. The four polyimides used in this study were synthesized from an indan‐containing diamine [5,7‐diamino‐1,1,4,6‐tetramethylindan (DAI)] with four dianhydrides [3,3′4,4′‐benzophenone tetracarboxylic dianhydride (BTDA), 3,3′4,4′‐oxydiphthalic dianhydride (ODPA), (3,3′4,4′‐biphenyl tetracarboxylic dianhydride (BPDA), and 2,2′‐bis(3,4′‐dicarboxyphenyl) hexafluoropropane dianhydride (6FDA)]. The gas‐permeability coefficients of these four polyimides changed in the following order: DAI–BTDA < DAI–ODPA < DAI–BPDA < DAI–6FDA. This was consistent with the increasing order of the fraction of free volume (FFV). Moreover, the gas‐permeability coefficients were almost doubled from DAI–ODPA to DAI–BPDA and from DAI–BPDA to DAI–6FDA, although the FFV differences between the two polyimides were very small. The gas permeability and diffusivity of these indan‐containing polyimides increased with temperature, whereas the permselectivity and diffusion selectivity decreased. The activation energies for the permeation and diffusion of O₂, N₂, CH₄, and CO₂ were estimated. In comparison with the gas‐permeation behavior of other indan‐containing polymers, for these polyimides, very good gas‐permeation performance was found, that is, high gas‐permeability coefficients and reasonably high permselectivity. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2769–2779, 2004     

Organosoluble polyimides and copolyimides based on 1,1‐bis[4‐(4‐aminophenoxy)phenyl]‐1‐phenylethane and aromatic dianhydrides

1,1‐Bis[4‐(4‐aminophenoxy)phenyl]‐1‐phenylethane (BAPPE) was prepared through nucleophilic substitution reaction of 1,1‐bis(4‐hydroxyphenyl)‐1‐phenylethane and p‐chloronitrobenzene in the presence of K₂CO₃ in N,N‐dimethylformamide, followed by catalytic reduction with hydrazine and Pd/C. Novel organosoluble polyimides and copolyimides were synthesized from BAPPE and six kinds of commercial dianhydrides, including pyromellitic dianhydride (PMDA, I_a ), 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA, I_b ), 3,3′,4,4′‐ biphenyltetracarboxylic dianhydride (BPDA, I_c ), 4,4′‐oxydiphthalic anhydride (ODPA, I_d ), 3,3′,4,4′‐diphenylsulfonetetracarboxylic dianhydride (DSDA, I_e ) and 4,4′‐hexafluoroisopropylidenediphthalic anhydride (6FDA, I_f ). Differing with the conventional polyimide process by thermal cyclodehydration of poly(amic acid), when polyimides were prepared by chemical cyclodehydration with N‐methyl‐2‐pyrrolidone as used solvent, resulted polymers showed good solubility. Additional, I_a,b were mixed respectively with the rest of dianhydrides (I_c–f) and BAPPE at certain molar ratios to prepare copolyimides with arbitrary solubilities. These polyimides and copolyimides were characterized by good mechanical properties together with good thermal stability. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2082–2090, 2000     

Syntheses and properties of organosoluble polyimides based on 5,5′‐bis[4‐(4‐aminophenoxy)phenyl]‐4, 7‐methanohexahydroindan

A series of organosoluble aromatic polyimides (PIs) was synthesized from 5,5′‐bis[4‐(4‐aminophenoxy)phenyl]‐4,7‐methanohexahydroindan (3) and commercial available aromatic dianhydrides such as 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA), 4,4′‐oxydiphthalic anhydride (ODPA), 4,4′‐sulfonyl diphthalic anhydride (SDPA), or 2,2′‐bis(3,4‐dicarboxyphenyl) hexafluoropropanic dianhydride (6FDA). PIs (III_c–f), which were synthesized by direct polymerization in m‐cresol, had inherent viscosities of 0.83–1.05 dL/g. These polymers could easily be dissolved in N,N′‐dimethylacetamide (DMAc), N‐methyl‐2‐pyrrolidone (NMP), N,N‐dimethylformamide (DMF), pyridine, m‐cresol, and dichloromethane. Whereas copolymerization was proceeded with equivalent molar ratios of pyromellitic dianhydride (PMDA)/6FDA, 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA)/6FDA, or BTDA/SDPA, or ½ for PMDA/SDPA, copolyimides (co‐PIs), derived from 3 and mixed dianhydrides, were soluble in NMP. All the soluble PIs could form transparent, flexible, and tough films, and they showed amorphous characteristics. These films had tensile strengths of 88–111 MPa, elongations at break of 5–10% and initial moduli of 2.01–2.67 GPa. The glass transition temperatures of these polymers were in the range of 252–311°C. Except for III_e, the 10% weight loss temperatures (T_d) of PIs were above 500°C, and the amount of carbonized residues of the PIs at 800°C in nitrogen atmosphere were above 50%. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1681–1691, 1999     

Aromatic Copolyimides Containing Perylene Units

Perylene-containing copolyimides have been synthesized by one-step polycondensation reaction under high temperature of two different aromatic diamines with a mixture of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) and 4,4'-hexafluoroisopropylidene diphthalic anhydride (6FDA). The copolyimides were soluble in polar amidic solvents and their solutions gave flexible thin films when spread onto glass plates. Very thin films obtained by spin coating had smooth surfaces and were self-organized into vertically segregated structures. The polymers were highly thermostable, their decompositions being above 470 °C and displayed reasonable high glass transition temperature values. After being excited with UV light, the polymers emitted light in the bluish and green-yellow domains.     

Synthesis of copolyimides based on room temperature ionic liquid diamines

Block copolyimides based on aromatic dianhydrides and diamines copolymerized with diamino room temperature ionic liquid (RTIL) monomers were synthesized over a range of compositions. Specifically, two diamino RTILs, 1,3‐di(3‐aminopropyl) imidazolium bis[(trifluoromethyl)sulfonyl] imide ([DAPIM] [NTf₂]) and 1,12‐di[3‐(3‐aminopropyl) imidazolium] dodecane bis[(trifluoromethyl) sulfonyl] imide ([C₁₂ (DAPIM)₂] [NTf₂]₂) were synthesized using a Boc protection method. The two RTILs were reacted with 2,2‐bis(3,4‐carboxylphenyl) hexafluoropropane dianhydride (6FDA) to produce 6FDA‐RTILs oligomers that formed the RTIL component for the block copolyimides. The oligomers were reacted with 6FDA and m‐phenylenediamine (MDA) at oligomer concentration from 6.5 to 25.8 mol % to form block copolyimides. Increasing the concentration of the 6FDA‐RTIL oligomer in the block copolyimides resulted in a decrease in the thermal degradation temperature, glass transition temperature and an increase in the density. The gas permeability of the RTIL based block copolyimide decreased but the ideal permeability selectivity for CO₂/CH₄ gas pair increased relative to the pure 6FDA‐MDA. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4036–4046, 2010     

Dielectric properties of oxydianiline‐based polyimide thin films according to the water uptake

For polyimide thin films, the dielectric properties were investigated with the capacitance and optical methods. The dielectric constants of the 4,4′‐oxydianiline (ODA)‐based polyimide thin films varied from 2.49 to 3.10 and were in the following decreasing order: 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA)–ODA > 1,2,4,5‐benzenetetracarboxylic dianhydride (PMDA)–ODA > 4,4′‐hexafluoroisopropylidene diphthalic dianhydride (6FDA)–ODA. According to the absorption of water, the diffusion coefficients in the films varied from 4.8 × 10^?10 to 7.2 × 10^?10 cm²/s and were in the following increasing order: BPDA–ODA < PMDA–ODA < 6FDA–ODA. The dielectric constants and diffusion coefficients of the polyimides were affected by the morphological structures, including the molecular packing order. However, because of the water uptake, the changes in the dielectric constants in the polyimide thin films varied from 0.49 to 1.01 and were in the following increasing order: BPDA–ODA < 6FDA–ODA < PMDA–ODA. Surprisingly, 6FDA–ODA with bulky hexafluoroisopropylidene groups showed less of a change in its dielectric constant than PMDA–ODA. The total water uptake for the polyimide thin films varied from 1.43 to 3.19 wt % and was in the following increasing order: BPDA–ODA < 6FDA–ODA < PMDA–ODA. This means that the changes in the dielectric constants in the polyimide thin films were significantly related to the morphological structure and hydrophobicity of hexafluoroisopropylidene groups. Therefore, the morphological structure and chemical affinity in the polyimide thin films were important factors in controlling the dielectric properties. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2190–2198, 2002     

Photosensitive fluorinated polyimides with a low dielectric constant based on reaction development patterning

The fluorinated polyimide PI(6FDA/HFBAPP) was prepared by the reaction of 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA) with 2,2‐bis[4‐(4‐aminophenoxy)phenyl]hexafluoropropane (HFBAPP) in 1‐methyl‐2‐pyrrolidone/toluene. A multiblock copolyimide with both fluorinated and rigid‐rod segments, PI(6FDA/HFBAPP)(BPDA/2‐DMB), was prepared by the addition of a second dianhydride, 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA), and a second diamine, 2,2′‐dimethylbenzidine (2‐DMB), to the polyimide main chain. The potential lithographic performance of photosensitive polyimides composed of nonphotosensitive fluorine‐containing polyimides and photosensitive diazonaphthoquinone (DNQ) was studied on the basis of a new imaging principle recently proposed by our laboratory, that is, reaction development patterning. Neat PI(6FDA/HFBAPP) showed a low dielectric constant (?) of 2.41 and a low dissipation factor (tan δ) of 0.0027 at 20 GHz, and a 10‐μm resolution of the fluorinated polyimide/DNQ system was demonstrated with reactive development with a solution including ethanolamine after ultraviolet exposure. Although slight changes in the dielectric properties were observed in the presence of DNQ residues, these values (? = 2.63 and tan δ = 0.0033 at 20 GHz) were low enough for use in microelectronic applications. However, PI(6FDA/HFBAPP)(BPDA/2‐DMB), having a lower coefficient of thermal expansion (CTE; 33 ppm/°C) than PI(6FDA/HFBAPP) (49 ppm/°C), exhibited good positive photosensitivity, whereas the relatively low‐CTE multiblock copolyimide displayed a much higher ? value (3.48 at 1 MHz) than the highly fluorinated polyimide (2.88 at 1 MHz). A film consisting of PI(6FDA/HFBAPP)(BPDA/2‐DMB) and the remaining DNQ derivatives showed a CTE value comparable to that of the neat polyimide film. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 861–871, 2003     

含全氟环丁烷环可溶性聚酰亚胺的合成与表征

以乙酰氨基苯酚为原料,经过BrCF2CF2Br氟烷基化、Zn催化脱卤、热环化二聚,以及水解去保护,合成了一种含全氟环丁烷环的二胺单体1,2,3,3,4,4-六氟-1,2-双[4-(氨基)苯氧基]环丁烷.用该单体分别与酯环二酐双环[2·2·1]辛烷-2,3,5,6-四羧基2,3,5,6-二酐(BHDA)、芳香性二酐3,3′,4,4′-联苯四酸二酐(BPDA)和3,3′,4,4′-二苯酮四酸二酐(BTDA)通过“一步法”制备了3种新型含全氟环丁烷环聚酰亚胺.通过粘度测试、溶解性实验、FT-IR、热失重分析(TGA)和差热扫描量热(DSC)分析等手段,对所合成的聚酰亚胺的结构与性能进行了表征.结果显示该类聚酰亚胺可溶于大多数常用极性有机溶剂,热分解温度高于480℃,其中两种聚合物玻璃化温度低于150℃,表明含全氟环丁烷环聚酰亚胺具有良好的溶解性和可加工性.     

Improvement of thermoplasticity for s‐BPDA/PDA by copolymerization and blend with novel asymmetric BPDA‐based polyimides

Asymmetric biphenyl type polyimides (PI) derived from 2,3,3′,4′‐biphenyltetracarboxylic dianhydride (a‐BPDA) and p‐phenylenediamine (PDA) or 4,4′‐oxydianiline (ODA) show higher T_gs, and much better thermoplasticity than the corresponding isomeric PIs from symmetric 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (s‐BPDA). In addition, a‐BPDA‐derived PIs are completely amorphous owing to their bent chain structures and highly distorted conformations, whereas the PIs from s‐BPDA are semicrystalline. a‐BPDA‐derived PIs possessing these properties or the a‐BPDA monomer were used as a flexible blend component or a comonomer to improve the insufficient thermoplasticity of semirigid s‐BPDA/PDA homo polymer. The blends composed of s‐BPDA/PDA (80%) with a‐BPDA‐derived PIs (20%), as well as the s‐BPDA/PDA‐based copolymer containing 20% a‐BPDA, showed a certain extent of thermoplasticity above the T_gs without causing a decrease in T_g. In addition, these blends and copolymer provided comparatively low thermal expansion coefficient (ca. 18 ppm). The improved film properties for the blends are related to good blend miscibility. On the other hand, when s‐BPDA/ODA was used as a flexible matrix polymer instead of a‐BPDA‐derived PIs, the 80/20 blend film annealed at 400°C exhibited no prominent softening at the T_g. This result arises from annealing‐induced crystallization of the flexible s‐BPDA/ODA component. Thus, these results revealed that a‐BPDA‐derived PIs are promising candidates as matrix polymers for semirigid s‐BPDA/PDA for the present purpose. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2499–2511, 1999     

Gas transport properties of 6FDA-TMPDA/MOCA copolyimides

The gas permeation behavior of 2,2′-bis(3,4′dicarboxyphenyl) hexafluoropropane dianhydride(6FDA)-2,4,6-trimethyl-1,3-phenylenediamine (TMPDA)/4,4′-methylene bis(2-chloroaniline) (MOCA) copolyimides was investigated by systematically varying the diamine ratios. All the copolyimides were soluble in most of the common solvents. The gas permeabilities and diffusion coefficients decreased with increasing MOCA content; however, the permselectivity of gas pairs such as H₂/N₂, O₂/N₂, CO₂/CH₄ was enhanced with the incorporation of MOCA moiety. Moreover, all of the copolyimides studied in this work exhibited performance near, lying on or above the existing upper bound trade-off line between permselectivity and permeability.     

含氟及硫醚基团聚酰亚胺光波导材料的合成及表征

通过分子设计,合成了含三氟甲基及硫醚基团的二胺单体4,4'-双(4-胺基-2-三氟甲基苯硫基)二苯硫醚(6FSEDA),利用其与6种芳香二酐单体:3,3',4,4'-联苯四羧酸二酐(BPDA)、4,4'-氧双邻苯二甲酸酐(ODPA)、3,3',4,4'-二苯酮四酸二酐(BTDA)、4,4'-(六氟异丙基)-苯二酸酐(6FDA)、3,3',4,4'-二苯硫醚四酸二酐(DTDA)及3,3',4,4'-二苯砜四酸二酐(DSDA)经一步法合成了一系列含氟及硫醚基团的聚酰亚胺(PI),并对其结构与性能进行了研究.结果表明,该系列PI的玻璃化温度Tg(DSC)在199.8～231.7℃范围,5%和10%热失重的温度(N2氛围)分别在491℃和517℃以上,在400～700 nm的可见光波长范围内具有优异的光学透明性,在光通讯波段(1310 nm和1550 nm处)均无明显吸收,且在这两个波长处测得的平均折射率范围分别为1.5401～1.6142和1.5389～1.6124,在波长632.8 nm测得的双折射范围为0.0012～0.0045.可见,含氟及硫醚基团聚酰亚胺薄膜具有良好的热稳定性和光学性能.     

共聚聚酰亚胺膜材料的合成及其气体渗透性能研究

以2,2′-双(3,4-二羧基苯基)六氟丙烷二酐(6FDA)作为二酐单体,1,3-苯二胺(mPDA)和2,6-二氨基甲苯(2,6-DAT)为二胺单体,采用溶液共缩聚方法合成了一系列新型共聚聚酰亚胺(6FDA-2,6-DAT/mPDA),该类聚合物均能溶于DMF、DMAc、NMP等极性非质子溶剂中,具有较好的成膜性.测试了H2、N2、O2、CH4、CO25种气体在6FDA-2,6-DAT/mPDA共聚聚酰亚胺致密膜中的渗透性能.结果显示,该系列共聚物具有优异的分离性能.在35℃,0.2 MPa下,H2/N2、O2/N2、CO2/CH4的分离性能均接近或突破Robeson上限.     

New thermally stable and organosoluble heterocyclic poly(naphthaleneimide)s

As majority of polyheteroarylenes based on bis(naphthalic anhydrides), are difficult to process due to their infusiblity and insolubility in common organic solvents and solubility only in strong acids, this study is concerned with the synthesis and properties of new, easily processable polyimides and copolyimides containing naphthalene and oxadiazole rings. These polymers have been synthesized and their properties have been compared with regard to the influence of oxadiazole and naphthalene units on their physical properties. The polyimides were prepared by polycondensation reaction in solution of the aromatic diamines containing preformed oxadiazole ring with two dianhydrides having naphthalene units, at high temperature. Also, copolyimides were prepared by using a mixture of each naphthalene‐containing dianhydride, with hexafluoroisopropylidene‐dianhydride in the polycondensation reaction with the same diamino‐oxadiazoles. Most of the resulting polyimides and copolyimides were soluble in polar amidic solvents and in less polar solvents, and their solutions gave flexible films when spread onto glass plates. The thermal stability and glass transition temperature of these polyimides and copolyimides were measured and compared. The quality and the roughness of the spin‐coated films of these polymers were investigated by atomic force microscopy. The photoluminescence properties of the polymers in solution were studied to determine the color of emission. The UV absorption was also studied to determine the Stokes shift, and hence the possible reabsorption effects. The properties of the present polyimides make them attractive for applications in advanced optoelectronics and other related fields. Copyright © 2009 John Wiley & Sons, Ltd.     

Preparation and characterization of organosoluble copolyimides based on a pair of commercial aromatic dianhydride and one aromatic diamine, 1,2-bis(4-aminophenoxy)-4-tert-butylbenzene, series

 A series of copolyimides with high molecular weights, excellent mechanical properties, heat-resistant properties, and good solubilities in organic solvents were synthesized from six kinds of commercial dianhydrides and 1,2-bis(4-aminophenoxy)-4-tert-butylbenzene. Monomers for synthesizing insoluble polyimides and monomers for synthesizing soluble polyimides were used to synthesize semialternating copolyimides with arbitrary solubilities. Fifteen kinds of soluble copolyimides were synthesized through chemical or thermal cyclodehydration. These copolyimides were found to be easily soluble as well as able to be processed by casting from solutions such as N-methyl-2- pyrrolidone, N,N-dimethylacetamide, dimethylformamide, dimethyl sulfoxide, m-cresol, and tetrahydrofuran. The easily dissolved characteristics of this series of copolyimides stemmed from the tert-butyl group, the ortho-linked aromatic unit, and the ether group within 4-tert-butylbenzene. Besides, when the dianhydride molecules used contained organosoluble groups and were mixed at varying molar ratios, the solubilities in organic solvents could be greatly enhanced. The copolyimides could improve the processability of polymers, while maintaining or increasing their excellent mechanical properties and heat-resistant properties. Received: 21 July 2000 Accepted: 13 December 2000     

Synthesis of polyimide and poly(imide-benzoxazole) in polyphosphoric acid

A polyimide made from 4,4′-diaminodiphenyl ether (ODA) and 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) was synthesized in polyphosphoric acid. Although the polymerization proceeded heterogeneously, a polyimide with an inherent viscosity of 0.90 was obtained, and a tough and flexible film was made from this polyimide. This polymerization was a one-step reaction including polycondensation and imidization; this was also confirmed by a model reaction between aniline and phthalic anhydride. Utilizing this polymerization method, 3,3′-dihydroxy-4,4′-diaminobiphenyl and 2 mol of 4-aminobenzoic acid were reacted in PPA, then BPDA was reacted to obtain an alternate copolymer containing imide and oxazole rings. This reaction gave a homogeneous solution of the poly(imide-benzoxazole). © 1993 John Wiley & Sons, Inc.     

A study on the effect of spirocyclic structures in the main chain on the physical properties of copolyimides

A series of copolyimides were prepared from two alicyclic dianhydrides having the common molecular formula C₁₀H₈O₆, rel‐[1S,5R,6R]‐3‐oxabicyclo[3.2.1]octane‐2,4‐dione‐6‐spiro‐3′‐(tetrahydrofuran‐2′,5′‐dione) (DAn) and c‐3‐carboxymethyl‐r‐1,c‐2,c‐4‐cyclopentanetricarboxylic acid 1,4:2,3‐dianhydride (TCAAH), with p‐phenylenediamine (PPD) by a conventional two‐step procedure. With increasing DAn fractions in the backbones, the copolyimides showed better film formability, enhanced solubility, increased glass transition temperatures and birefringences, and decreased average refractive indices. The unsymmetric spiroalicyclic structure of DAn might be responsible for these results. Films of copolyimides obtained by both thermal and chemical imidization were fully transparent and were colorless or pale yellow depending on the film thickness.     

一步法合成高T_g可溶含偶氮三嗪发色团的新型侧链含氟聚酰亚胺

采用一步法合成了一系列侧链含偶氮三嗪发色团的新型含氟聚酰亚胺FPI(x),并研究其溶解性能、热性能以及光学性能.该系列聚酰亚胺具有优良的溶解性能,不仅溶于NMP,DMAc,DMF,DMSO等强极性非质子性溶剂,而且还溶于THF和乙二醇单甲醚等低沸点溶剂.FPI(x)系列共聚聚酰亚胺具有较高的玻璃化转变温度(T_g,在544～562K之间),且与主链中染料发色团的含量无关.所有聚酰亚胺都表现出优良的高温稳定性,其5%热失重温度(T₅)比T_g高出100K以上,基本能满足电场极化对聚合物材料热稳定性的要求.另外,FPI(x)系列聚酰亚胺的紫外截止吸收波长小于500nm,即在大于500nm波长范围内基本透明.其面内折光指数n_TE随着染料发色团含量的增加而逐渐增加.     

温度和压力对六氟二酐型聚酰亚胺的透气性能的影响

本文研究了温度和压力对五种六氟二酐（６ＦＤＡ）型聚酰亚胺膜对Ｈ_２、ＣＯ_２、Ｏ_２、Ｎ_２和ＣＨ_４五种气体透过性能的影响．在３０－１００℃区间，五种聚酰亚胺的透气系数与温度的关系均符合Ａｒｒｈｅｎｉｕｓ关系式；在０．３－１．２ＭＰａ区间，压力对透气系数的影响很小．６ＦＤＡ－４，４＇－二氨基二苯酮（ＤＡＢＰ）和６ＦＤＡ－３，３＇－二甲基二苯甲烷二胺（ＤＭＭＤＡ）在１００℃仍然具有较大的透气选择系数，是比较好的气体分离膜材料．     

Improvement of CO2/CH4 separation characteristics of polyimides by chemical crosslinking

Uncrosslinked and crosslinked polyimides and copolyimides have been synthesized in order to increase selectivity without an unacceptable loss in permeability. The goal was to reduce undesirable effects caused by CO₂ induced swelling in CO₂/CH₄ separation processes by stabilizing the polyimide structure with crosslinks. In the polymerization reaction 6FDA (4,4′-(hexafluoroisopropylidene)diphthalic anhydride) was used as dianhydride monomer and mPD (m-phenylene diamine) and DABA (diamino benzoic acid) were used as diamine monomers. With copolyimides containing strong polar carboxylic acid groups (i.e. 6 FDA–mPD/DABA 9:1) reduced plasticization was seen up to a pure CO₂ feed pressure of 14 atm, presumably due to hydrogen bonding between the carboxylic acid groups. By chemical crosslinking of the free carboxylic acid groups of the 6FDA–mPD/DABA 9:1 with ethylene glycol, the swelling effects due to CO₂ can be reduced at least up to a pure CO₂ feed pressure of 35 atm. With increasing degree of crosslinking, increasing CO₂/CH₄ selectivity was found because of reduced swelling and polymer chain mobility. By using ethylene glycol as a crosslinking agent, CO₂ permeability was not significantly lowered because the reduced chain mobility was compensated by the additional free volume caused by the crosslinks.     

Sul-containing fluorinated polyimides for optical waveguide device

Novel sul-containing fluorinated polyimides have been synthesized by the reaction of 2,2′-bis-(trifluoromethyl)-4,4′-diaminodiphenyl sulfide (TFDAS) with 1,4-bis-(3,4-dicarboxyphenoxy)benzene dianhydride (HQDPA), 2,2′-bis-(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), 4,4′-oxydiphthalicanhydride (ODPA) or 3,4,3′,4′-biphenyl-tetracarboxylic acid dianhydride (s-BPDA). The fluorinated polyimides, prepared by a one-step polycondensation procedure, have good solubility in many solvents, such as N-methyl-2-pyrrolidinone (NMP), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), cyclohexanone, tetrahydrofuran (THF) and m-cresol. The molecular weights (M_n's) and polydispersities (M_n/M_w's) of polyimides were in the range of 1.24 × 10⁵ to 3.21 × 10⁵ and 1.59–2.20, respectively. The polymers exhibit excellent thermal stabilities, with glass-transition temperatures (T_g) at 221–275 °C and the 5% weight-loss temperature are above 531 °C. After crosslinking, these polymers show higher thermal stability. The films of polymers have high optical transparency. The novel sul-containing fluorinated polyimides also have low absorption at both 1310 and 1550 nm wavelength windows. Rib-type optical waveguide device was fabricated using the fluorinated polyimides and the near-field mode pattern of the waveguide was demonstrated.