Metal ion additive–polyimide interactions employing thermogravimetry

Solutions of poly(amic acid), a polyimide precursor prepared from 3,3′,4,4′-benzophenone tetracarboxylic acid dianhydride and 4,4′-oxydianiline, containing metal ions such as Pd, Pt, and Sn in a variety of chemical states were prepared. The polymer–metal ion solutions and each component thereof were analyzed by thermogravimetry. Summation of the calculated contribution of each component of the polymer solution mass loss curve yields a calculated TG curve. Subtraction of the calculated curve from the actual curve for the polyamic acid–metal ion solution results in a difference TG curve. From the difference TG curve information about polymer/additive interactions can be obtained.     

Preparation and Characterization of Aminopropylsilatrane Endcapped Polyimide Films

γ-Aminopropylsilatrane (APS)/γ-aminopropyltriethoxysilane (APTES) end capped polyimide films were prepared by thermal imidization method. Polyamic acid (PAA) was prepared by the reaction of 4,4′-oxydianiline (ODA) with 4,4′-oxydipthalicdianhydride (ODPA) using dimethylacetamide (DMAc) as solvent. The end group of prepared PAA was capped by different percentage of APS/APTES. The polyimide films were characterized by different advanced instrumental techniques for chemical/physical properties. APS end capped PI films show better thermal and mechanical properties and air permeability than APTES end capped polyimide films.     

新型聚酰亚胺薄膜的制备及其性能研究

采用2,4,6-三甲基间苯二胺（TMmPDA）、4,4＇-二氨基二苯醚（DADPE）和3,3＇,4,4＇-四羧基联苯二酐（BP-DA）为主原料,摩尔比为1∶4∶5,合成得到了三甲基间苯二胺型聚酰胺酸（TMPAA）溶液,涂膜,热亚胺化,制得了三甲基间苯二胺型聚酰亚胺（TMPI）薄膜,并对其粘度、力学性能等进行了研究。     

Non-Destructive In Situ Analysis of Interface Processes and Thin Film Growth

Optical second harmonic generation (SHG) was applied to monitor the growth of films of polyamic acid on polycrystalline gold substrates. Different diamines such as 4,4′-oxydianiline (ODA), 4,4′-diaminodiphenyl disulfide (DAPS) and 4,4′-diaminobiphenyl (benzidine) were codeposited from the gas phase with pyromel-litic dianhydride (PMDA). Depending on the diamine, the second harmonic signal varies differently during formation of the polymer/metal interface and the subsequent film growth. A three-layer model which takes into account the optical properties of thin films reveals that the shape of the thickness-dependent SH signal is related to the orientation of the molecules in the film. A fit of the experimental data based on the model indicates a structural transition that occurs several tens of nanometers above the substrate for PMDA/ODA and PMDA/DAPS. The experiments demonstrate that SHG can be applied to monitor the growth of thin films and to extract structural information.     

聚酰胺酸合成工艺与聚酰亚胺膜制备及表征

聚酰亚胺是一类新型高性能的聚合物材料,是由聚酰胺酸脱水环化而成,因此高分子量的聚酰胺酸是获得高性能PI的前提。探讨了聚酰胺酸合成过程中的影响因素,得出了合成高分子量的聚酰胺酸的最佳工艺条件为:均苯四羧酸二酐与4,4' 二氨基二苯醚摩尔比为1.015～1.020∶1,反应温度20℃,反应时间为3h,聚酰胺酸在N 甲基 2 吡咯烷酮中的特性粘度为0.62dL/g左右。采用热转化法将聚酰胺酸脱水环化制备成均苯型聚酰亚胺膜,通过差示扫描量热法、红外光谱等进行了表征,其玻璃化转变温度为365～385℃,拉伸强度达192.4MPa,表明得到的聚酰亚胺膜具有优良的机械性能。     

Adhesion and interface studies between copper and polyimide

The adhesion and interface structure between copper and polyimide have been studied. Polyimide films were prepared by spinning a polyamic acid solution (Du Pont PMDA-ODA) in an NMP solvent onto a Cu foil, followed by thermal curing up to 400°C. The adhesion strength was measured by a 90° peel test. The peel strength of 25 μm thick Cu foil to 25 μm thick polyimide substrate was about 73 g/mm with the peel strength decreasing with increasing polyimide thickness. Cross-sectional TEM observation revealed very fine Cu-rich particles distributed in the polyimide. Particles were not found closer than 80-200 nm from Cu boundary. These Cu-rich particles were formed as a result of reaction of polyamic acid with Cu during thermal curing. We attribute the high peel strength to interfacial chemical bonding between Cu and polyimide. This behavior is in contrast to vacuum-deposited Cu onto fully cured polyimide.     

Synthesis and properties of the amino‐functionalized multiple‐walled carbon nanotubes/polyimide nanocomposites

The 1,6‐hexanediamine‐functionalized multi‐walled carbon nanotubes(a‐MWNTs)/polyimide(PI) nanocomposite films were prepared through in‐situ polymerization followed by mixture casting, evaporation, and thermal imidization. To increase the compatibility of carbon nanotubes with the matrix polyimide, a‐MWNTs was used as the filler. According to the results, a‐MWNTs were homogeneously dispersed in the nanocomposite films. With the incorporation of a‐MWNTs, the mechanical properties of the resultant films were improved due to the strong chemical bonding and interfacial interaction between a‐MWNTs and 4,4′‐oxydiphthalic anhydride(ODPA)/4,4′‐Oxydianiline(ODA) polyimide matrix. The thermal stability of the a‐MWNTs/polyimide nanocomposite was also improved by the addition of a‐MWNTs. The electrical tests showed a percolation threshold at about 0.85 vol% and the electrical properties were increased sharply. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Polyimide blend alignment layers for control of liquid crystal pretilt angle through baking

Polyimide films were used for liquid crystal (LC) alignment layers to control LC pretilt angles over the full range (8°-90°). The pretilt angles could be controlled using polyimide films prepared from polyamic acid for vertical LC alignment and using polyimide blend films prepared from two types of polyamic acids, one for vertical LC alignment and the other for planar LC alignment, by changing the baking times ranging from 40 to 180 min at 230 °C. The polyimide blend film could control the pretilt angle better than the polyimide prepared from just one polymer component. The LC alignment behavior was well correlated with the wettability of the polyimide films due to the fragmentation of the long alkyl side group on the polyimide surfaces by the baking process.     

Influence of curing temperature on properties of the polyacrylonitrile/polyimide composite films

A series of polyacrylonitrile/polyimide (PAN/PI) composite films with different PAN contents are prepared under given curing temperatures (250, 300, 350, and 400°C). The microstructure of the composite films is observed by SEM, and the thermal, dielectric and mechanical properties of the composite films are determined. The results show that the self‐assembly behavior of polyamic acid gives rise to connected network structure in the composite films and the variations in the microstructure of the composite films cured at different temperatures show important effects on the properties of PAN/PI composite films. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40283.     

含羟基聚酰亚胺改性环氧胶的制备及性能研究

将3,3'-二氨基-4,4'-二羟基联苯(DADHBP)、2,2-双(3-氨基-4-羟基苯基)六氟丙烷(BAH-PFP)和3,3',4,4'-四羧酸二苯醚二酐(ODPA)、3,3',4,4'-四羧酸二苯甲酮二酐(BTDA)单体聚合,再经亚胺化得到含羟基聚酰亚胺(HPI)粉末,采用傅里叶红外光谱对其进行了表征。由HPI、烯丙基双酚A、双马来酰亚胺、2-乙基-4-甲基咪唑与N,N,N',N'-四缩水甘油基-4,4'-二氨基二苯甲烷(TGDDM)共聚反应制得胶粘剂,并对胶粘剂的热性能、力学性能及吸水性进行了研究,结果表明:该胶拉伸剪切强度为21.1 MPa,固化后吸水率为0.49%。通过凝胶化时间法计算胶粘剂的表观活化能为64.5 kJ/mol。     

Synthesis and properties of BCDA‐based polyimide–clay nanocomposites

Bicyclo[2.2.2]oct‐7‐ene‐2,3,5,6‐tetracarboxylic dianhydride (BCDA)‐based polyimide–clay nanocomposites were prepared from their precursor, namely polyamic acid, by a solution‐casting method. The organoclay was prepared by treating sodium montmorillonite (Kunipia F) clay with dodecyltrimethylammonium bromide at 80 °C. Polyamic acid solutions containing various weight percentages of organoclay were prepared from 4,4′‐(4,4′‐isopropylidenediphenyl‐1,1′‐diyldioxy)‐dianiline and BCDA in N‐methyl‐2‐pyrrolidone containing dispersed particles of organoclay at 20 °C. These solutions were cast on a glass plate using a Doctor's blade and then heated subsequently to obtain nanocomposite films. The nanocomposites were characterized using Fourier transform infrared spectroscopy, differential scanning calorimetry, thermal mechanical analysis, dynamic mechanical analysis, polarizing microscopy, scanning electron microscopy, transmission electron microscopy, wide‐angle X‐ray diffraction (WAXD) and thermogravimetric analysis. The glass transition temperature of the nanocomposites was found to be higher than that of pristine polymer. The coefficient of thermal expansion of the nanocomposites decreased with increasing organoclay content. WAXD studies indicated that the extent of silicate layer separation in the nanocomposite films depended upon the organoclay content. Tensile strength and modulus of the nanocomposite containing 1% organoclay were significantly higher when compared to pristine polymer and other nanocomposites. The thermal stability of the nanocomposites was found to be higher than that of pristine polymer in air and nitrogen atmosphere. Copyright © 2007 Society of Chemical Industry     

Surface-Enhanced Raman Scattering As an In-Situ Probe of Polyimide/Silver Interphases

The molecular structure of interphases formed by chemically curing the polyamic acid of pyromellitic dianhydride (PMDA) and oxydianiline (ODA) against meta-aminothiophenol (m-ATP)-primed silver substrates was determined using surface-enhanced Raman scattering (SERS) and reflection-absorption infrared spectroscopy (RAIR). It was found that m-ATP was adsorbed dissociatively onto silver substrates through the sulfur atoms. When polyamic acid was deposited onto silver substrates pretreated with m-ATP, acid groups of the polyamic acid combined with amino groups of m-ATP to form ammonium carboxylate salts near the interphase. SERS and RAIR results indicated that the structure of the interphase was significantly different from that of the bulk polymer. Chemical curing of the polyamic acids located in the interphase was suppressed because of the formation of ammonium carboxylate salts. However, the bulk of the polyamic acid films was highly cured to form polyimide. It was also found that more isoimide groups were formed when thin polyamic acid films were chemically cured in acetic anhydride/pyridine solutions than in acetic anhydride/triethylamine solutions.     

聚酰胺酸溶液酰亚胺化程度控制及其对PI薄膜性能影响

乙酐/吡啶混合溶剂加入均苯四羧酸二酐(PMDA)–4,4’–二氨基二苯醚(ODA)型聚酰胺酸溶液中,发生化学酰亚胺化,得到酰胺酸-酰亚胺共聚物(PA–I)。通过旋转黏度计和傅立叶变换红外光谱的系统研究,当酰亚胺化程度达到26%左右时,溶液发生相分离。选择合适的溶液浓度、乙酐含量、反应时间,能够对PA–I均相溶液的酰亚胺化程度实施控制。用不同酰亚胺化程度的PA–I溶液进行热酰亚胺化,获得聚酰亚胺薄膜。研究结果表明,酰亚胺化程度较高的PA–I溶液,所制聚酰亚胺薄膜呈现出较高有序程度的聚集态结构,较高的拉伸强度和拉伸弹性模量。     

均苯型共聚聚酰亚胺薄膜的制备及其性能

以2,2′-双[3-苯基-4(4-氨基苯氧基)苯基]丙烷(BPAPOPP)、4,4′-二胺基二苯醚和均苯四甲酸酐为原料,采用两步法共缩聚制备了一系列共聚聚酰亚胺薄膜。采用红外光谱仪、差示扫描量热仪等分析了薄膜的结构,利用静态热机械分析仪分析了薄膜的性能。结果表明:制备的聚酰亚胺薄膜具有较低的玻璃化转变温度;随着BPAPOPP含量的增加,薄膜的热性能有所降低,但其溶解性能得到了改善。     

Synthesis and characterization of polyamide-imides

A series of thermally stable, tough, linear polyimides containing amide linkages was prepared. The new polyamide-imides were synthesized by reacting a group of isomers of diaminobenzanilide (DABA) with various dianhydrides, such as 4,4′-oxydiphthalic anhydride (ODPA), 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), and 2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA). The resulting polyamide-acids were thermally or chemically converted to the polyamide-imide (PAI). Twelve polyimides were synthesized from unsubstituted and N-methyl substituted amide diamines and their properties were compared with previously made polyamide-imides and the polyimide LARC-TPI. These polyimides exhibited high inherent viscosities and glass transition temperatures. They were made into tough, flexible films of which some showed good thermal stability and resistance to organic solvents. Overall, the mechanical properties of the PAI films were comparable to those of LARC-TPI with the 4,4′-systems exhibiting exceptional properties and crystallinity. These materials have potential as high temperature films, coatings and fibers, as well as molding and laminating resins.     

Determination of poisson's ratio for polyimide films

The Poisson's ratios of polyamic acid and polyimide films were determined using a high pressure gas dilatometer. In this technique, a sample is held at constant length and a hydrostatic pressure is applied to the sample. The resulting change in stress on the sample with applied pressure provides a measure of Poisson's ratio. For fully cured polyimide films based on pyromellitic dianhydride and oxydianiline, Poisson's ratio was measured to be 0.34 at approximately 1% strain. This value increases to 0.48 as the strain is increased to 5%.     

Laser interferometric measurement of polymer thin film thickness changes during processing

A simple interferometric technique is described for monitoring thickness changes in solution-cast polymer films as they are dried and cured. This paper follows a freshly spun solution of polyamic acid in NMP as it is converted into a cured polyimide film of 6 μm in thickness. The technique is shown to be nearly quantitative despite the effects of thermal expansion and cure-related refractive index changes.     

Linear and networked blends and copolymers of polyimide

Preparation and characterization of blends and copolymers of a fluorinated polyimide with network constituents is reported. 4,4′‐Hexafluoroisopropylidene diphthalic anhydride and 4,4′‐diaminodiphenyl ether (6FDA–DDE) polyimide were used as the linear hosts and mellitic acid hexamethyl ester ‐ 4,4′‐diaminodiphenyl ether (MAHE–DDE) was employed as the network constituent for the blend and copolymer. Cast films of the polyimides were characterized by FTIR, XPS, DMA, and TGA. The multifunctional nature of MAHE facilitated crosslinking among the constituents. Both blends and copolymers showed significant improvement in the storage modulus and glass transition temperature relative to that observed for the 6FDA homopolymer. The occurrence of a single glass transition temperature for the blends suggests that they were at least partially miscible. Presence of low molecular weight species in the copolyimides, combined with steric hindrance to crosslinking, may have resulted in the existence of an optimum in the amount of the network components for improving the mechanical properties. Inclusion of network components is presented as a facile method for improving the desirable properties of polyimide. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3000–3008, 2006     

多壁碳纳米管/聚酰亚胺复合材料制备及其性能研究

聚酰亚胺的前聚体,聚酰胺酸,是通过4,4-二氨基二苯醚(ODA)与3,3,4,4二苯甲酮四羧酸二酐(BTDA)反应制备的。未改性的、酸改性和胺改性的多壁碳纳米管(MWCNT)被分别地单独加入到聚酰胺酸溶液中,并加热至300℃,从而制成聚酰亚胺/碳纳米管复合材料。扫描型电子显微镜(SEM)和透射电子显微镜(TEM)的显微照片表明,酸改性的多壁碳纳米管和胺改性多壁碳纳米管在聚酰亚胺基体中被均匀一致地分散开。通过对酸和胺改性的多壁碳纳米管MWCNTS对多壁碳纳米管/聚酰亚胺复合材料的表面和体积电阻率的影响进行了研究。了解到该纳米复合材料的表面电阻率ITES从1.28×10^(15)Ω/cm^(2)(纯聚酰亚胺),降到7.59×10^(6)Ω/cm^(2)(26.98%的未改性的多壁碳纳米管含量)。除此之外,添加多壁碳纳米管影响了纳米复合材料的玻璃化转变温度。改性多壁碳纳米管意义就是提高了纳米复合材料的机械性能。多壁碳纳米管/聚酰亚胺复合材料的拉伸强度从10^(2)MPa(纯的聚酰亚胺)增加到134 MPa(6.98%酸改性多壁碳纳米管/聚酰亚胺复合材料)。     

Morphology and size control of inorganic particles in polyimide hybrids by using SiO2-TiO2 mixed oxide

Polyimide/inorganic hybrids were prepared by sol-gel reaction starting from tetraethoxysilane (TEOS), and tetrabutyl titanate (TBT) in the solution of polyamic acid in N,N-dimethylformamide. The hybrid films were obtained by the hydrolysis-polycondensation of TEOS and TBT in polyamic acid solution, followed by the elimination of solvents and imidization process. Binary polyimide/SiO₂ and polyimide/TiO₂ hybrids, as well as ternary polyimide/SiO₂-TiO₂ hybrids (with varied ratio of SiO₂ to TiO₂) were prepared to study the effects of the recipes and inorganic components on the morphologies of the polyimide hybrids. Transparent films with much higher inorganic content can be obtained in ternary polyimide hybrids, while lower inorganic content in binary hybrids. The results also indicate that the inorganic particles are much smaller in the ternary systems than in the binary systems, the shape of the inorganic particles and the compatibility for polyimide and inorganic moieties are varied with the ratio of the inorganic moieties in the hybrids. The completely imidization temperature of the polyamic acid was delayed, and furthermore, the thermal stability of polyimide was enhanced through the incorporation of the inorganic moieties in the hybrid materials.