【作者】 黄孝华；

【导师】 颜德岳； 黄卫；

【作者基本信息】 上海交通大学 ， 高分子化学与物理， 2011， 博士

【摘要】 聚酰亚胺是一类含有酰亚胺环的高性能高分子材料,具有优异的热稳定性、机械性能及电性能,广泛应用于航空航天、汽车、微电子等高科技领域中。但由于传统的聚酰亚胺溶解性差、加工温度高,因而其应用受到了一定限制。为满足一些特殊领域的发展需求,针对功能性聚酰亚胺材料,如具有高溶解性、高透明性、低介电常数或高折射率的聚酰亚胺的研究和开发已成为目前最引人注目的热点之一。本论文简述了聚酰亚胺的发展过程,并在分子水平上探讨了聚酰亚胺分子结构特点以及各种改性方法对聚酰亚胺功能性的影响。在此基础上,从芳香二胺和二酐单体的分子设计与合成出发,成功地将一系列特殊结构和取代基如硫醚基、三氟甲基、多烷基和扭曲非共平面结构等引入聚酰亚胺主链中,制得多种综合性能优异的聚酰亚胺材料。采用FT-IR、NMR、质谱和元素分析等表征手段对所制备的单体和聚合物结构进行了分析和确认,并利用UV-Vis、TGA、DSC、DMA、广角X射线衍射和ATR耦合菱镜仪等多种仪器对聚酰亚胺材料各项性能如溶解性能、机械性能、介电性能、吸湿率和折射率等进行了详细表征和探讨。主要研究工作和结论如下:1、以2,2-双(4-羟苯基)六氟丙烷(简称六氟双酚A)、4-氯硝基苯和2-氯-5-硝基三氟甲苯等为原料,经亲核取代、Newman-Kwart重排、水解、氧化还原等五步有机反应设计合成了两种新型芳香二胺单体:2, 2-双[4-(4-胺基苯硫基)苯基]六氟丙烷(5)和2, 2-双[4-(4-胺基-2-三氟甲基苯硫基)苯基]六氟丙烷(7),然后与一系列芳香二酐单体通过“一步法”高温溶液缩聚反应,成功制备了主链中含硫醚基和六氟异亚丙基,或含侧三氟甲基的可溶性聚酰亚胺材料(PI 9a-f系列和PI 10a-f系列),并对所得聚酰亚胺材料的各项性能进行了表征和研究。结果表明,所得聚酰亚胺不仅溶于NMP、DMF、DMAc、DMSO及m-Cresol等高沸点、强极性溶剂中,还溶于CHCl3、THF甚至丙酮等低沸点溶剂中;其重均分子量在5.4×104 ~ 2.52×105之间,分子量分布指数在1.32 ~ 2.87之间,可通过溶液浇注法制得透明的韧性聚酰亚胺薄膜;其玻璃化转变温度在207 ~ 266℃之间,在氮气氛围中其5%和10%热失重温度分别在499 ~ 525℃和522 ~ 543℃之间,800℃时的残炭量为34 ~ 52 %;其薄膜的拉伸强度为60 ~ 93 MPa,断裂伸长率为7.0 ~ 12.3%,杨氏模量为0.90 ~ 1.47 GPa;截止波长在330 ~ 387 nm之间,400 nm波长后透光率在80%以上;通过ATR耦合菱镜仪测得聚合物薄膜的平均折射率在1.5116 ~ 1.6031之间,双折射在0.0025 ~ 0.011之间,介电常数在2.51 ~ 2.83之间;所得聚酰亚胺的吸湿率在0.05 ~ 0.76%之间。可见,该类聚酰亚胺不仅具有良好的溶解性,还具有优异的耐热性能、机械性能、光学性能、介电性能及较低的吸湿率,潜在的应用前景广泛。2、以4-溴苯酐、2,2-双(4-巯苯基)六氟丙烷为原料,通过取代、水解反应得到中间体2,2-双[4-(3,4-二羧基苯硫基)苯基]六氟丙烷(6FTAPSP),然后在乙酐中脱水闭环得到新型芳香二酐单体2,2-双[4-(3,4-二羧基苯硫基)苯基]六氟丙烷二酐(6FDAPSA)。然后进一步与各种芳香二胺单体通过“一步法”高温溶液缩聚反应,制得了一系列主链含硫醚及六氟异异丙基的聚酰亚胺材料。测试结果表明:该类聚酰亚胺材料具有优异的综合性能。在室温下其具有良好的溶解性,不仅溶于NMP、DMF、DMAc、DMSO及m-Cresol等强极性、高沸点溶剂中,还能溶于CHCl3及THF等低沸点溶剂,其重均分子量和分子量分布分别在1.1×105 ~ 2.4×105和1.9 ~ 2.4之间;该系列聚酰亚胺具有良好的耐热稳定性,其玻璃化转变温度范围在206 ~ 258℃之间,热分解起始温度范围在480 ~ 540℃之间,在氮气氛围中5%和10%热失重范围分别载471 ~ 530℃和484 ~ 548℃之间,800℃下的残炭率大于54%;所得聚酰亚胺可以通过溶液浇注法制成具有优异的力学性能韧性薄膜,其拉伸强度在69 ~ 78 MPa,断裂伸长率均大于7%;该聚酰亚胺薄膜具有优异的光学透明性,大部分薄膜样品颜色浅,有的甚至接近无色,UV-Vis测试表明其截止波长范围为401 ~ 421 nm,在440 nm以上波段的透光率都在80%以上;ATR耦合菱镜测试表明,该类薄膜的平均折射率在1.5462 ~ 1.5993之间,双折射在0.0035 ~ 0.0125之间;该类聚酰亚胺具有较低的介电常数(2.63 ~ 2.81)和吸水率(小于0.56%)。3、以2-氯-5-硝基三氟甲苯和4,4’-二巯基二苯硫醚为原料,经过缩合和还原两步反应制得一种新型芳香二胺单体:4,4’-双(4-胺基-2-三氟甲基苯硫基)二苯硫醚(6FSEDA),然后与六种不同的芳香二酐单体经“一步法”高温溶液缩聚反应,制备了一系列主链含硫醚结构和侧三氟甲基取代基的可溶性聚酰亚胺材料。研究结果表明:所得聚酰亚胺材料具有较好的溶解性、耐热性和光学性能。在室温下,该类聚酰亚胺材料易溶于DMF、DMAc、NMP、DMSO及m-Cresol等强极性有机溶剂,可以通过溶液浇铸法得到透明韧性薄膜。其玻璃化温度为197 ~ 235℃(DMA)及200 ~ 232℃(DSC),在氮气氛围中5%和10%热失重的温度分别在491℃和517℃以上,800℃时的残炭率在30 ~ 63%之间;截止波长为380 ~ 417 nm,在波长大于450 nm时具有良好的光学透明性;另外,近红外光谱测试显示该类聚酰亚胺在光通讯波段(1310 nm和1550 nm)具有较小的吸收,较宽的通讯波段发射“窗口”;在1310 nm及1550 nm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632.8 nm测得的双折射范围为0.0012 ~ 0.0045。所得聚酰亚胺材料的吸湿率均小于0.85%。4、以1,4-二巯基苯和4-溴苯酐为起始原料,经取代、水解、缩合等反应成功合成了一种含硫醚结构的芳香二酐单体:1,4-双(3,4-二羧基苯硫基)苯二酐(2SDEA)。然后进一步与各种商品化芳香二胺单体通过“二步法”,经高温热亚胺化制得一类主链含有硫醚结构的聚酰亚胺薄膜材料。该类聚酰亚胺薄膜具有较好的热稳定性,玻璃化转变温度在205 ~ 266℃之间,在氮气氛围中,5%和10%热失重温度范围分别为508 ~ 546℃和538 ~ 558℃,800℃长率和杨氏模量分别在58 ~ 83 MPa、10 ~ 19%和0.65 ~ 1.05 GPa之间;该聚酰亚胺薄膜材料具有较好的光学透明性,其截止波长为352 ~ 400 nm,在460 nm处的透射率均超过80%;在632.8 nm处测得的平均折射率nAV和双折射值Δn范围分别为1.6823 ~ 1.7404和0.0085 ~ 0.0120,相对应的介电常数εopt为3.11 ~ 3.33;材料的吸水率均小于1.03%。5、以2-异丙基苯胺和4-甲基苯甲醛为起始原料,经一步偶联反应成功合成了一种含异丙基和4-甲基苯基取代基的芳香二胺单体:3,3’-二异丙基-4,4’-二胺基苯基-4’’-甲基甲苯(PAPMT),然后与一系列商品化芳香二酐通过“一步法”高温缩聚反应制得一类主链含3,3’-二异丙基和4-甲基甲苯结构的新型聚酰亚胺材料。研究结果表明:该类聚酰亚胺材料具有高可溶性、高耐热性、高光学透明性、低地介电常数及低吸湿率等性能;在室温下能溶于NMP、DMF、DMAc、DMSO、m-Cresol、CHCl3和THF等大多数有机溶剂;玻璃化转变温度Tg较高,其范围在262 ~ 308℃之间,在空气或氮气氛围下10%的热失重温度分别为485 ~ 503℃和489 ~ 507℃,氮气氛围中800℃时的残炭率均在61%以上;其截止波长为302 ~ 365 nm,透过率为80%的起始波长范围为385 ~ 461 nm;1MHz下测得的介电常数为2.73 ~ 3.23;材料的吸水率介于0.13 ~ 0.46%之间。更多还原

【Abstract】 Aromatic polyimides are a class of high performance polymeric materials containing imide rings, which are well-known for their excellent thermal stability, electrical and mechanical properties. They are widely used in many high technology fields, such as aerospace, automobile and microelectronics etc. However, the applications of conventional aromatic polyimides are often limited because of their poor solubility and high processing temperatures. In order to overcome these problems and meet the need of development in some special areas, more and more researches have been focused on the preparation of functional polyimides, such as good solubility, high transparence, low dielectric constant, high refractive index and so on.In this paper, we summarized the development of polyimides, dicussed the molecular structural characteristics of polyimides and the effect of various structural modification methods on the properties of functional polyimides. On the basis of molecular design, six novel monomers including aromatic diamines and aromatic dianhydrides and their corresponding series of functional polyimides were synthesized successfully. Some special molecular structures and substituents were introduced into the polyimide backbones, such as trifluoromethyl groups, thioether groups, bulky alkyl groups and non-coplanar structures. The chemical structures of the resulting monomers and polyimides were confirmed by FT-IR, NMR, MS and elementary analysis. The solubility, thermal property, mechanical property, aggregate structures, optical properties, dielectric property, and water absorption were also investigated and discussed. The details and key conclusions are described as follows:1. Two novel aromatic diamines containing thioether groups and hexafluoro isopropylidene group, or trifluoromethyl pendent groups, 2,2-bis[4-(4-aminophenylsulfanyl)phenyl]- hexafluoropropane (5) and 2,2-Bis[4-(4-amino-2-trifluoromethylphenylsulfanylphenyl)]- hexafluoropropane (7) were synthesized via nucleophilic substitution, Newman-Kwart rearrangement, hydrolyzation, oxidation and reduction reactions using 2,2-Bis(4-hydroxyphenyl)- hexafluoropropane, 4-chloronitrobenzene and 2-Chloro-5- nitrobenzotrifluoride as starting materials. Then they were polymerized with various aromatic dianhydrides through the one-step high-temperature polycondensation procedure to produce two series of the functional polyimide (PI 9a-f and 10a-f). The various properties of the resulting functional polyimides were investigated and characterized in detail. All the functional polyimides easily dissolved in strong polar aprotic solvents such as N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N,N-dimethylacetamide (DMAc) and m-Cresol at room temperature. Most of them could still be soluble in low boiling point organic solvents such as CHCl3, tetrahydrofuran (THF) and even partially soluble in acetone. The weight-average molecular weight and molecular weight distribution were in the range of 5.4×104 ~ 25.2×104 and 1.32~2.87, respectively. The transparent strong and flexible PI films were obtained by the solution casting method. They exhibited excellent thermal stability with the glass transition temperature in the range of 207 ~ 266 oC, and the weight loss temperature of 5% and 10% were in the range of 499 ~ 525 oC and 522 ~ 543 oC, respectively. These polyimides films exhibited highly optical transparency with the UV cutoff wavelength of 330 ~ 387 nm and the transmittance is higher than 80% at 401 nm. Moreover, the polymer films showed outstanding mechanical properties with the tensile strengths of 60 ~ 93 MPa, elongation at breaks of 7.0 ~ 12.3% and Young’s modulus of 0.90 ~ 1.47 GPa. The average refractive index and the birefringence of the polyimides were in the range of 1.5116 ~ 1.6031 and 0.0025~0.0112, respectively. The dielectric properties were estimated from the average refractive indices with in the range of 2.51 ~ 2.83. The polyimides also had low water absorption of 0.05 ~ 0.76%.2. A novel aromatic dianhydride with thioether group and hexafluoro isopropylidene group, 2,2-bis[4-(3,4-dicarboxyphenylsulfanyl)phenyl]hexafluoropropane dianhydride (6FTAPSP) was synthesized successfully by nucleophilic substitution, hydrolyzation and closed loop reactions using 2,2-bis(4-thiolphenyl)hexafluoropropane and 4-bromophthalic anhydride as starting materials. Then they were employed to prepare some novel polyimides with several aromatic diamines via the one-step high-temperature polycondensation. The resulting polyimides displayed excellent comprehensive properties. At room temperature, they could be dissolved both in strong polar aprotic solvents (such as NMP, DMF, DMAc, DMSO, m-Cresol) and low boiling point solvents (such as CHCl3 and THF). The weight-average molecular weights and molecular weight distributions were in the range of 1.1×105 ~ 2.4×105 and 1.9 ~ 2.4, respectively. All the polyimides were able to prepare into the transparent, flexible and strong films by the solution casting method. These polyimides films showed good thermal stability with the glass transition temperature in the range of 206 ~ 258 oC, and the weight loss temperature of 5% and 10% were above 471 oC and 484 oC, respectively. In addition, the char yields of all polyimides at 800 oC in nitrogen still maintained 54% or more of their original weights. Moreover, these PI films exhibited highly optical transparency with the UV cutoff wavelength of 401 ~ 421 nm and the transmittance is higher than 80% at 440 nm. They also showed the outstanding mechanical properties with the tensile strengths of 69~78 MPa, elongation at breaks over 7%. The average refractive index and the birefringence of the polyimides were in the range of 1.5462 ~ 1.5993 and 0.0035 ~ 0.0125, respectively. And good dielectric properties with low dielectric constants of 2.63 ~ 2.81 were estimated from the average refractive indices. The water absorption of polyimides was lower than 0.56%.3. A novel aromatic diamine containing thioether groups and trifluoromethyl pendent groups, 4,4’-bis(4-amino-2-(trifluoromethyl)phenylsulfanyl)diphenyl sulfide (6FSEDA), was synthesized by the nucleophilic substitution and reduction reaction with 1-chloro-4-nitro-2-(trifluoromethyl)- benzene and 4,4’-thiobisbenzenethiol as starting material. Then it was polymerized with six various dianhydrides via one-pot high-temperature polycondensation to produce a series of polyimides. The resulting polyimides were soluble in conventional polar organic solvents, such as NMP, DMF, DMAc, m-Cresol, and some of them are even soluble in CDCl3 and acetone. The glass transition temperatures of plyimides were in the range of 197 ~ 235 oC (by DMA) and 200 ~ 232 oC (by DSC), respectively. They were able to keep stable over 400 oC and the char yields at 800 oC were between 30 ~ 63%. In addition, the PI films showed good optical transparency in the visible light region (450 ~ 700 nm) with the cutoff wavelengths range of 380 ~ 417 nm, and little absorption at the optoco-mmunication wavelengths of 1310 nm and 1550 nm. Furthermore, the average refractive indices (nAV) of the polyimide films were measured at 1310 nm and 1550 nm by Variable Angle Spectroscopic Ellipsometer (VASE), and the results of the nAV were 1.5401 ~ 1.6142 and 1.5389 ~ 1.6124, respectively. The birefringence (△n) of the polyimide films were obtained in the range of 0.0012 ~ 0.0043 by the ATR prism coupling device at 632.8 nm. Moreover the water absorption of the polyimides all was less than 0.85%.4. A series of novel aromatic polyimides were synthesized and characterized from a newly synthesized thioether-containing dianhydride, 1,4-bis(3,4-dicarboxy-phenylenesulfanyl)-benzene dianhydride (2SDEA) derived from 1,4-benzenedithiol and 4-bromophthalic anhydride as starting material, and various diamines by a two-step polycondensation reaction. All the flexible and tough films PI1-5 derived from 2SDEA were thermally stable up to 500 oC both in air and nitrogen. Their glass transition temperatures are in the range of 205 to 266 oC. And the polymer films presented excellent mechanical properties, the tensile strengths, elongation at breaks, and Young’s moduli were 58 ~ 83 MPa, 10 ~ 19% and 0.65 ~ 1.05 GPa, respectively. In addition, these polyimides presented good transparency with the UV cutoff wavelengths of 352 ~ 400 nm and the transmittance is higher than 80% at 460 nm. Moreover the polyimides endowed themselves with high average refractive indices (nAV) from 1.6823 to 1.7404 and low birefringence (Δn) between 0.0085 and 0.0120 at 632.8 nm. The corresponding dielectric constants calculated from the average refractive indices were in the range of 3.11 ~ 3.33. The water absorption of the polyimides was all less than 1.03%.5. A novel aromatic diamine, 3,3’-diisopropyl-4,4’-diaminophenyl-4’’-methyltoluene (PAPMT) with 4-methylphenyl pendent group and isopropyl side groups, was designed and synthesized by a one-step coupling reaction using 2-isopropylaniline and 4-methylbenzaldehyde as staring materials. Then it was polymerized with various aromatic dianhydrides via a one-pot high-temperature polycondensation to produce a series of aromatic polyimides. These polyimides PI1-5 showed excellent solubility, they could be quickly soluble in NMP, DMF, DMAc, DMSO, m-Cresol, CHCl3 and THF at room temperature. And the PI films were nearly colorless and exhibited high optical transparency, with the UV cutoff wavelength in the range of 302 - 365 nm and the starting wavelength of 80% transparency in the range of 385 ~ 461 nm. Furthermore, they also possessed good thermal and thermo-oxidative stability with 10% weight loss temperatures in the range of 489 ~ 507 oC in nitrogen atmosphere, and the glass transition temperatures of all polyimides are in the range of 262~308 oC. They also showed low dielectric constants (2.73 ~ 3.23 at 1 MHz) and low moisture absorption (0.13 ~ 0.46 %).更多还原