【作者】 齐胜利；

【导师】 金日光； 武德珍；

【作者基本信息】 北京化工大学 ， 材料学， 2008， 博士

【摘要】 聚酰亚胺银的复合薄膜以其表面银层无与伦比的反射性和电导率,再加上聚酰亚胺基体本身优异的热稳定性和物理机械性能,以及其其它各方面的优异性能（柔软、轻质、高强）,在航空航天和微电子等许多领域具有广阔的应用前景,成为近年来广泛研究的多功能材料之一。本文采用两种不同的方法,原位一步自金属化法和直接离子交换自金属化法,制得了表面金属化的聚酰亚胺银复合薄膜,对复合薄膜的表面性能、热性能和机械性能进行了表征,考察了薄膜表面金属化过程中的各种影响因素,并探讨了相关的机理。在原位一步自金属化法中,以均苯四甲酸酐/4,4’-二胺基二苯醚（PMDA/ODA）基聚酰亚胺为基体,以三氟乙酰丙酮银（AgTFA）作为银的母体制备出了表面金属化的聚酰亚胺银复合薄膜。薄膜的表面反射性能随着含银量的增加呈现出上升的趋势,但是反射率整体较低,只有20～40%。在快速升温固化时,得到了具有很好导电性的薄膜,其表面电阻达到了5Ωsq^-1左右。但是由于基体刚性太大,薄膜的热稳定较差,300℃热处理4 h以上时发生严重降解。合成了均苯四甲酸酐—3,3’,4,4’-二苯甲醚四酸二酐/4,4’-二胺基二苯醚（PMDA-ODPA/ODA）基的嵌段和无规共聚型聚酰亚胺,考察了共聚组成和共聚序列对金属化复合薄膜性能的影响。其中,嵌段共聚型聚酰亚胺由于两组分保持了自己的独立特性,产生了协同作用,所得到的薄膜同时具有了较好的反射率和导电性。薄膜最高反射率达到了55%以上,电阻值最低达到了5Ωsq^-1。而无规共聚型聚酰亚胺由于两者实现了分子水平混合,破坏了各组分的特性,所得到的薄膜最大反射率只有42%,而且不导电。复合薄膜很好地保持了母体聚酰亚胺薄膜的力学性能和热性能。实验通过扫描电镜（SEM）和X射线光电子能谱（XPS）阐明了复合薄膜的表面反射性能在固化过程中呈现出阶梯形变化的原因,建立起了薄膜的表面形貌与表面性能之间的关系。采用透射电镜（TEM）和X射线衍射（XRD）跟踪了复合薄膜中银颗粒的还原聚集长大和银层的形成过程,讨论了银层的形成机理。开创了直接离子交换自金属化法,通过将半干性的聚酰胺酸薄膜在银盐的水溶液中进行离子交换载银然后热处理制得了双面银金属化的聚酰亚胺薄膜。实验分别以PMDA/ODA、ODPA/ODA和3,3’,4,4’-二苯甲酮四酸二酐/4,4’-二胺基二苯醚（BTDA/ODA）基聚酰亚胺为基体,以硝酸银（AgNO₃）、氟化银（AgF）和银氨络离子（[Ag（NH₃）₂]⁺）为银源,制得了聚酰亚胺银的复合薄膜。结果表明聚酰亚胺基体和银盐的结构对复合薄膜的表面反射性能和导电性能都具有很大的影响。其中以BTDA/ODA基聚酰亚胺为基体时,所制得的银化薄膜达到了高反射高导电的水平。性能最优异的是BTDA/ODA-AgF体系的复合薄膜,其上下两个表面的反射率分别超过了80%和100%,表面电阻达到了0.6Ωsq^-1和0.2Ωsq^-1。金属化效率最高的是以碱性的[Ag（NH₃）₂]⁺为银源的情况,在很低的银盐浓度（0.01 M）和很短的离子交换时间（5 min）下即实现了蹦さ挠行Ы鹗艋?薄膜上下表面的反射率分别达到了81.8%和93.1%,表面电阻达到了0.6Ωsq^-1。但是复合薄膜上下两面均呈现出一定的差异,下表面的反射率和导电性往往高于上表面,而且金属化通常发生较早,研究发现这是由于预聚体薄膜在制备的过程中其上表面发生了轻微的亚胺化作用所致。通过SEM、XRD、XPS、TEM和紫外/可见（UV/Vis）分光光度仪表征对薄膜的表面金属化过程进行了研究,弄清了银的还原聚集过程,建立了薄膜的表面形貌、表面组成和表面性能之间的关系。观察到了薄膜浅表层的银颗粒向薄膜表面迁移的现象,指出了这种作用对形成表面银层的贡献很弱。并通过差示扫描量热（DSC）、热失重（TGA）、XPS和SEM分析证明了聚酰亚胺表面高反射高导电银层的形成是在银催化下、氧气辅助的表层聚合物降解和表层银颗粒自加速聚集共同作用的结果。表面银层与＞（?）[1 3 5]（?）XPS表明银与聚合物之间有很强烈的化学成键作用,但是其主要以面心立方（FCC）晶型的单质银的形式存在于薄膜表面。对薄膜的离子交换过程进行了深入的研究,通过傅立叶红外（FTIR）和XPS揭示了聚酰胺酸分子与银离子之间所发生了各种反应。发现了金属离子掺杂后聚酰胺酸大分子的交联行为;建立了一种方法测定了聚酰胺酸在离子交换过程中的质量损失,发现纯水对聚酰胺酸的破坏作用很小,而银离子则有强烈催化加速聚酰胺酸分子水解断链的作用。金属化后的复合薄膜在空气中的热稳定性有较大的下降（降低约130～160℃）,但是其基本上保持了母体薄膜优异的机械性能。将离子交换自金属化法的应用进行了拓展,以水溶性的PMDA/ODA聚酰胺酸为载体,以AgNO₃为银源,在银的加入量不高于1 mol%时,制得了单分散的立方形纳米银颗粒。通过控制热处理时间可以控制银颗粒的尺寸在90～150 nm之间。更多还原

【Abstract】 Surface-silvered polyimide（PI）film,due to the combination of the excellent thermal and mechanical properties of the polyimide matrix and the unmatched optical reflectivity and electrical conductivity of the surface silver（Ag）layer as well as its many other outstanding performances such as flexibility,light weight,and high strength,has been found widely attractive in aerospace and microelectronic industry and therefore has been extensively studied in recent years.In this dissertation,we report our efforts on the preparation of such silver-metallized polyimide films via two different techniques,in-situ single-stage self-metallization and direct ion-exchange self-metallization.The surface reflectivity and conductivity,thermal and mechanical properties of the composite film were characterized.Factors influencing the film metallization process and related mechanism were investigated.With the in-situ single-stage self-metallization protocol,surface-silvered polyimide film has been prepared using pyromellitic dianhydride/ 4,4’-oxydianiline（PMDA/ODA）-based polyimide as the matrix and （1,1,1-trifluoro-2,4-pentadionato）silver（AgTFA）as the silver precursor. Surface reflectance of the metallized film increases with increasing silver concentration.However,the reflectivity for the films prepared from this system is relatively low,with a value in the range of 20～40%.Electrical conductivity was obtained only under rapid thermal treatment cycle and the films were prepared with surface resisitivity of ca.5Ωsq^-1.However,because of the rigid macromolecule structure,the thermal stability of the metallized film was greatly reduced and serious decomposition would occur on the film after 4 h at 300℃.Block and random pyromellitic dianhydride - 4,4’-oxydiphthalic anhydride /4,4’-oxydianiline（PMDA-ODPA/ODA）-based copolyimides were synthesized in our work and used as the matrix to investigate the influence of copolymerization ratio and sequence on the properties of the metallized films. For the silvered random copolyimide,only 40%reflectivity was achieved and no conductivity was observed.However,both reflectivity and conductivity were obtained on the block matrix with a maximum reflectivity over 55%and surface resistivity of ca.5Ωsq^-1,which is suggested to be due to the synergistic effect of the PMDA/ODA block chain and the ODPA/ODA block chain existing in the block copolyimide.The final metallized films retain the essential thermal and mechanical properties of the pristine polyimide film.The step-wise variation of reflectivity during the thermal curing cycle was fully clarified through scanning electron microscopy（SEM）and X-ray photoelectron spectroscopic（XPS）analysis.The relationship between surface properties and surface morphology has been established.Silver reduction, aggregation and the formation of surface silver layer has been traced in the work using transmission electron microscopy（TEM）and X-ray diffraction （XRD）.And the mechanism pertaining to the silver layer formation has been discussed.A direct ion-exchange self-metallization approach was developed in our work and double-surface-silvered polyimide film has been fabricated through the ion exchange of damp-dry poly（amic acid）（PAA）films in aqueous silver ion solution and subsequent thermal treatment.In this dissertation,three different polyimides including PMDA/ODA,ODPA/ODA and 3,3’,4,4’-benzophenonetetracarboxylic dianhydride - 4,4’-oxydianiline （BTDA/ODA）were used as the matrices and three different simple silver salts including silver nitrate,silver fluoride and silver ammonia complex cation were employed as the silver origins for the film preparation.The results suggest that both polyimide structure and silver structure have significant influence on the surface reflectivity and conductivity of the final metallized film.Films prepared using BTDA/ODA-based polyimide as the matrix achieved very high reflectivity and conductivity.The optimum one was the film prepared from the BTDA/ODA-AgF system,with maximum reflectivity over 80%/ 100%and surface resisitivity of 0.6 / 0.2Ωsq^-1on the upside and underside,respectively.Silver ammonia complex cation has the highest efficiency for polyimide silver metallization.Films with maximum reflectivity of 81.8%/ 93.1%and surface resistance of 0.6 / 0.6Ωsq^-1on the upside/underside could be fabricated by employing very dilute silver ion solution（0.01 M）and very short ion exchange time（5 min）.Surface differences were observed on the metallized film,that is,the reflectivity and conductivity of the underside are always superior to that of the upside.And surface metallization usually（?）curs earlier on the underside.It is suggested that slight imidizaiton occurring on the upside of the poly（amic acid）film should be responsible for all these differences.SEM,XRD,XPS,TEM and ultraviolet/visible（UV/Vis）analysis were carried out on the films cured at different thermal stage to investigate the film metallization process.We have clarified the silver reduction and aggregation process and established the relationships of surface properties with the surface morphology and the surface composition of the hybrid films.The migration of small silver particles from the near-surface bulk to the top surface of the film was observed by TEM in our work.However,we figure that this effect doesn’t play very important role in the formation of well-established silver layer.And we have demonstrated through differential scanning calorimetry（DSC）, thermogravimetry（TGA）,XPS and SEM analysis that the formation of highly reflective and conductive silver layers on polyimide film is a result of the silver-catalyzed and oxygen-assisted decomposition of the polymer overlayer and the self-accelerated aggregation of silver clusters on the film surface.The surface silver layers were well-boned to the underlying polyimide.XPS analysis indicates that there are strong chemical bonging interactions between the silver and the polymer groups.However,silver present on the surface mainly exists as native metal in the form of face-centered-cubic（FCC）crystal.The ion exchange process between poly（amic acid）and silver ions was extensively studied in our work.Detailed chemical interactions occurring between the macromolecule and silver ions have been disclosed through Fourier transform infrared spectroscopy（FTIR）and XPS analysis.A metal-ion-induced cross-linking behavior of the matrix was observed during the loading of silver into poly（amic acid）via ion exchange.We have developed a method and measured the mass loss of poly（amic acid）during the ion exchange process.The results indicate that water molecules have very weak damaging effect on the precursor,while the silver ions have strong catalytic and accelerated effect on the hydrolysis of poly（amic acid） molecules.Compared to the pristine film,the thermal stability of the hybrid films in air were ca.130～160℃degraded after the incorporation of silver.However,the final metallized film maintains the basic mechanical properties of the polyimide matrix.Recently,the application of the direct ion-exchange self-metallization approach was extended in our work.Monodispersed silver nanocubes have been fabricated via this method with silver adding amount no more than 1 mol%by employing water-soluble PMDA/ODA-based poly（amic acid）as the intermediate and silver nitrate as the silver origin.The size of silver particles could be controlled in the range of 90～150 nm by adjusting the thermal treatment time.更多还原