Poly(dimethylsiloxane)-polyimide blends in the formation of thick polyimide films

Thick polyimide layers can be formed by using some unique properties of poly(dimethylsiloxane)-polyimide (PDMS/PMDA–ODA) blends followed by surface modification and deposition of a second layer of polyimide precursor chemicals. The method is based on the micro-phase separation characteristics of these blends to yield surfaces that have PDMS-like character. Upon modification with UV/ozone treatment, a surface that is essentially SiO _x and hydrophilic in nature is produced. This surface is amenable to reaction and deposition of a second polyimide layer from polyimide precursors. The thicker polyimide layer has enhanced adhesion between the original layer of the blend and the new polyimide layer and this approach finds extensive applications for products that require thick polymer layers. Changes in surface energy for various blend compositions were monitored by measurement of advancing contact angle with de-ionized water. Contact angle for unmodified polyimide films was on the order of 70° and it increased to about 104° after blending with PDMS and curing. UV/ozone treatment reduced the contact angle of the doped polyimide to less than 5°. X-ray photoelectron spectroscopy (XPS) and angle resolved XPS (ARXPS) measurements were used to monitor the chemical compositions of the various surfaces. High-resolution XPS spectra in the Si2p region confirm the transformation of O–Si–C bonds in PDMS to SiO _x , where x is about 2. Scanning electron microscopy (SEM) of some selected samples shows that the blends contain phase separation of the polymers at the surfaces of the samples. Atomic force microscopy (AFM) of siloxane-free polyimide, and PDMS/PMDA–ODA blends both prior to and after UV/ozone exposure, show that the films are essentially flat at short treatment times (less than 60 min). AFM also reveals the separation of PDMS into micro-domains at the cured film surface and throughout the layer below the surface of the blended films. Adhesion of a subsequently deposited polyimide layer to the modified polyimide surface was found to be greatly improved when compared to the adhesion obtained for deposition onto a pristine polyimide surface.     

Synthesis, characterization, physicochemical and dielectric properties of siloxane, polyimide and their blends

Very low molecular weight polydimethylsiloxane (PDMS) has been synthesized and characterized by using Infrared spectroscopy (IR), nuclear magnetic resonance, thermogravimetric analysis (TGA) and differential scanning calorimetry. Molecular weight distribution of PDMS has been determined by using multiple angle light scattering and size exclusion chromatography while hydrodynamic radii have been determined by quasi elastic light scattering. Electrical properties fo PDMS were determined using broadband dielectric analyzer with variable temperature and frequency. Polyamic acid has been synthesized and characterized. Two polymers were blended at precursor stage and cured following unique time-temperature profile. Both the component in blends are characterized by using IR and TGA. Dielectric properties of both neat polyimide and its blend have been evaluated using broad band dielectric analyzer in variable temperature and frequency range. PDMS was found to dominate the surface characteristics of the blends as determined by scanning electron microscopy and optical microscopy. Possible mechanism of blend formation has been proposed wherein concurrent amicacid catalyzed equilbration and immobilization of siloxane moiety due to charge transfer complexation existing between the two componenets visualized to occur.     

Preparation and characterization of polyimide/ladder like polysiloxane hybrid films

Novel polyimide (PI)/ladder like polyphenylsilsesquioxane (PPSQ) hybrid films was prepared. PI was made from poly(amide acid) of 4, 4′’-diaminodiphenylether and pyromellitic dianhydride. PPSQ was prepared from phenyltrimethoxysilane through sol-gel process. The chemical structure of PPSQ was characterized by Fourier transform infrared and nuclear magnetic resonance. The coefficients of thermal expansion for the hybrid films decrease with the increasing content of PPSQ. The thermal and mechanical properties of the hybrid films were essentially similar to the neat PI.     

Laser Induced Periodic Structures on Polymer Surfaces

Subhalf micron (0.2 nm) space and amplitude linear periodic structures and an array of dot images are obtained with the Nd:YAG laser irradiation on Kapton polyimide films, poly(ethylene terephthalate) films, spin-coated polyimide films and others. Different from the excimer laser irradiation, which requires a polarizer, our solid state Nd:YAG laser source provides polarized beams without a polarizer with advantage over excimer laser irradiation. AFM and SEM studies have been carried out. XPS studies of laser exposed areas indicate no significant chemical reactions took place on exposed areas.     

正交设计法研究聚酰胺酸分子量及其影响因素

采用正交试验设计方法,研究了聚酰胺酸固体含量、反应温度、加料间隔时间和反应时间对聚酰胺酸分子量的影响,采用凝胶渗透色谱仪测试了不同反应条件下合成的聚酰胺酸的分子量。正交设计试验结果表明,合成最高分子量聚酰胺酸的反应条件为:反应温度为15℃,固体含量为8%,加料间隔时间为9min,反应时间为3h。在此基础上,使用TGA测试了由不同分子量聚酰胺酸合成的聚酰亚胺薄膜的热稳定性。试验结果显示,聚酰胺酸分子量越大,薄膜的热稳定性越好。     

Enhanced adhesion of plasma-sputtered copper films on polyimide substrates by oxygen glow discharge for microelectronics

Enhanced plasma-sputtered copper film adhesion onto polyimide substrates treated by oxygen glow discharge was investigated. The peel test demonstrates this improvement, with peel strengths of 0.7-1.2 g/mm for copper films prepared on un-modified polyimide substrates and 195.5-262.2 g/mm for copper films on oxygen plasma-modified polyimide substrates at certain plasma conditions. The enhanced adhesive strengths of plasma-sputtered copper films onto polyimide substrates by oxygen plasmas are due mainly to the increased surface energies of the polyimide substrates. Contact angle measurements indicate that the surface energies of polyimide substrates were greatly increased by oxygen plasmas. X-ray photoelectron spectroscopy analysis shows that the increased surface energies of polyimide substrates using oxygen plasmas occur because of the increased oxygen surface concentration and the increased C-O bond proportion.     

Atomic oxygen resistant phosphorus-containing polyimides for LEO environment

In this study, a series of polyimides had been prepared from bis-(4-aminophenoxyl) phenoxyl phosphine oxide (p-DAPO₄) with corresponding dianhydrides via two-stage polycondensation method. The inherent viscosities of the polyamide acid were in range of 0.43–0.92 dL/g, and atomic oxygen (AO) exposure experiment was conducted in a ground-based atomic oxygen effects simulation facility with the filament charge and bound of magnetic field to determine the AO erosion-resistant properties of the polyimide films. Field emission scanning electron microscopy (FE-SEM), attenuated total-reflection Fourier transform infrared spectrometer and X-ray photoelectron spectrometer were employed to characterize the change on the surface of films after AO exposure, and the mass loss of some phosphorus-containing polyimide films reduced to about 20% that of Kapton^? HN film as AO fluence of 4.14 × 10²⁰ atoms/cm². The morphologies of heave residues of the polyimide films acting as a barrier to further erosion could be obtained from FE-SEM. The results indicated that a phosphate-type layer was left on the surface of phosphorus-containing polyimide films after AO exposure.     

Protection of polymer from atomic-oxygen erosion using Al2O3 atomic layer deposition coatings

Thin films of Al₂O₃ grown using atomic layer deposition (ALD) techniques can protect polymers from erosion by oxygen atoms. To quantify this protection, polyimide substrates with the same chemical repeat unit as Kapton^® were applied to quartz crystal microbalance (QCM) sensors. Al₂O₃ ALD films with varying thicknesses were grown on the polyimide substrates. The ALD-coated polyimide materials were then exposed to a hyperthermal atomic-oxygen beam. The mass loss versus oxygen-atom exposure time was measured in situ by the QCM. Al₂O₃ ALD film thicknesses of ∼ 35 Å were found to protect the polymer from erosion.     

MFC-structured biodegradable poly(l-lactide)/poly(butylene adipate-co-terephatalate) blends with improved mechanical and barrier properties

Both polylactide (PLA) and poly(butylene adipate-co-terephthalate) (PBAT) are biodegradable polymers. They are thermoplastics which can be processed using conventional polymer processing methods. In this study, microfibrillar-reinforced composites (MFC) based on PLA/PBAT (PLA/Ecoflex^®) blends in different weight ratios were prepared under industry-relevant conditions by melt extrusion followed by continuous cold drawing of the extrudates. Strip-like specimens (films) and plates (laminates) of the drawn blends were prepared by compression molding (CM) at processing temperature above the melting temperature (T _m) of PBAT, but below T _m of PLA. SEM and WAXS observations show that the extruded blend components are isotropic, but become highly oriented after drawing, and they are converted into MFC-structured polymer–polymer composites after CM. An effect of PLA microfibrils on the non-isothermal crystallization of the Ecoflex during cooling from the melt, associated with the formation of crystalline regions of the matrix around the fibrils, was observed. Depending on the blend composition, the compression-molded samples possess a 3- to 7-time higher tensile strength as well as a 15–30 higher modulus than the neat Ecoflex. In addition, the MFC-structured plates exhibited superior barrier properties compared to the neat Ecoflex, e.g., the oxygen permeability decreased by up to 5 times.     

Preparation of nanoporous polyimide thin films via layer-by-layer self-assembly of cowpea mosaic virus and poly(amic acid)

Low dielectric (low-κ) materials are of key importance for the performance of microchips. In this study, we show that nanosized cowpea mosaic virus (CPMV) particles can be assembled with poly(amic acid) (PAA) in aqueous solutions via the layer-by-layer technique. Then, upon thermal treatment CPMV particles are removed and PAA is converted into polyimide in one step, resulting in a porous low-κ polyimide film. The multilayer self-assembly process was monitored by quartz crystal microbalance and UV-Vis spectroscopy. Imidization and the removal of the CPMV template was confirmed by Fourier transform infrared spectroscopy and atomic force microscopy respectively. The dielectric constant of the nanoporous polyimide film thus prepared was 2.32 compared to 3.40 for the corresponding neat polyimide. This work affords a facile approach to fabrication of low-κ polyimide ultrathin films with tunable thickness and dielectric constant.     

HECA/聚己内酯-环氧丙烷共混膜的生物降解研究

研究了羟乙基纤维素醋酸酯与己内酯－环氧丙烷共聚物共混物膜的生物降解过程,发现共混物膜的生物降解性能与其组成密切相关。共混膜的降解速率随着已内酯－环氧丙烷共聚物含量的增加而加快。在降解过程中,分了量较小的部分首先开始降解,而且降解的速度较快。分子量高的部分降解较慢,控制着整个共混膜的降解速率。     

聚酰亚胺薄膜的制备及其摩擦学性能研究

通过浸渍得到了聚酰胺酸薄膜,采用适当的方法对薄膜进行处理之后再进行热亚胺化得到聚酰亚胺薄膜.用DF-PM型动静摩擦系数精密测定装置考察所得到的聚酰亚胺薄膜的摩擦学性能.用SEM考察了聚酰亚胺薄膜的磨痕形貌和对偶Si3N4陶瓷球表面的转移膜的形貌.结果表明,聚酰亚胺薄膜在与Si3N4陶瓷球对磨时,由于在摩擦过程中,聚酰亚胺能够在对偶面上形成均匀的并且低剪切强度的转移薄膜,因此表现出了优异的减摩与抗磨性能.聚酰亚胺薄膜的摩擦和磨损行为主要取决于薄膜的制备条件.     

Preparation SnO₂ nanolayer on flexible polyimide substrates via direct ion-exchange and in situ oxidation process

Tin oxide (SnO(2)) nanolayers were formed on flexible polyimide (PI) substrate via direct ion-exchange and in situ oxidation process utilizing pyromellitic dianhydride/4,4'-oxidianiline-based poly(amic acid) films as polyimide precursor. During an ion-exchange process, stannous ions were doped into the precursor by immersion in ethanolic solution of stannous chloride. Subsequent thermal treatment of the tin(II)-containing precursor at a constant heating rate not only imidized poly(amic acid) to PI but also converted stannous ions into SnO(2) clusters, which diffused and aggregated onto the surface of polymer matrix, forming continuous tin oxide layers. Inductively coupled plasma (ICP) was used to investigate the ion-exchange process. Changes in chemical structure of the poly(amic acid) film and the crystal structure of tin oxides were analyzed by attenuated total reflection-Fourier transform infrared (ATR-FTIR) and X-ray diffraction (XRD). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to study the microstructure of the PI/SnO(2) nanocomposite films. The nanocomposite film maintained essential mechanical property and thermal stability of pristine PI films.     

High performance polyimide composite films prepared by homogeneity reinforcement of electrospun nanofibers

Highly aligned polyimide (PI) and PI nanocomposite fibers containing carbon nanotubes (CNTs) were produced by electrospinning. Scanning electron microscopy showed the electrospun nanofibers were uniform and almost free of defects. Transmission electron microscopy indicated that the CNTs were finely dispersed and highly oriented along the CNT/PI nanofiber axis at a relatively low concentration. The as-prepared well-aligned electrospun nanofibers were then directly used as homogeneity reinforcement to enhance the tensile strength and toughness of PI films. The neat PI nanofiber reinforced PI films showed good transparency, decreased bulk density and significantly improved mechanical properties. Compared with neat PI film prepared by solution casting, the tensile strength and elongation at break for the PI film reinforced with 2 wt.% CNT/PI nanofibers were remarkably increased by 138% and 104%, respectively. The significant increases in the overall mechanical properties of the nanofibers reinforced polyimide films can be ascribed to good compatibility between the electrospun nanofibers and the matrix as well as high nanofiber orientation in the matrix. Our study demonstrates a good example for fabricating high performance and high toughness polyimide nanocomposites by using this facile homogeneity self-reinforcement method.     

杂萘联苯聚醚酮改性双马来酰亚胺树脂体系的相行为

采用光学显微镜(OM)和扫描电镜(SEM)分别对杂萘联苯聚醚酮(PPEK)改性双马来酰亚胺树脂(BMI)体系的反应诱导相分离行为和固化产物的相结构进行了研究。结果表明,体系的相分离过程可能按旋节相分离机理进行并存在二次相分离现象;改变PPEK的含量,固化产物的相结构可实现由球形粒子结构到相反转结构的连续性变化。同时,考察了PPEK分子量及含量对固化树脂冲击强度的影响。结果表明,PPEK的加入可有效改善体系的韧性。     

Rapid treatment of polyimide film surfaces using high-density microwave plasma for enhancement of Cu layer adhesion

A high-density microwave plasma has been applied to the surface of polyimide (PI) films as a treatment to enhance the adhesion of sputter-deposited copper layers. A very short (∼5 s) exposure to Ar plasma enhanced the contact angle from 72° to ∼14°. X-ray photoelectron spectroscopy and atomic force microprobe measurements showed an increase in hydrophilic radicals (-OH, -CO) and surface roughness, respectively, following the plasma treatment. Peel strength tests of Cu layers deposited on plasma-treated polyimide films showed that the plasma treatment significantly enhanced Cu layer adhesion.     

Thin polymer films from polyimide vacuum thermal degradation with and without a glow discharge

Polyimide-like thin films were deposited by thermal degradation of polyimide with and without simultaneous activation by a glow discharge excited using an r.f. planar magnetron. The films deposited without discharge are similar in composition to conventional polyimide, whereas the deposition with plasma results in cross-linked coatings with composition typical for plasma polymers e.g. prepared by r.f. sputtering of polyimide. AFM reveals rough surface topography for the films evaporated without plasma. The application of plasma leads to very smooth plasma polymer films.     

Blends of PP/PE co‐octene for modified atmosphere packaging applications

The aim of this work was to obtain films of polypropylene (PP)/polyethylene co‐octene (POE) blends and study the influence of their composition and mixing conditions on final morphology and ultimate properties (thermal, mechanical, oxygen and water vapour transmission rates). Scanning electron microscopy showed segregation of POE domains in the PP matrix. Thermal analysis indicated that the addition of POE modified neither the melting temperature nor the crystallinity of PP in the pressed films. It was found that permeabilities of films were mainly related to POE content rather than morphological features. For the maximum POE concentration used (40%), the oxygen permeability increased up to ∼100% from that of neat PP. A similar trend was found for water vapour permeability. Rigidity of blends dropped significantly with the addition of POE although their ductility slightly increased when compared to pure PP. No significant effect of blend preparation conditions on these properties was found. Mechanical and permeability characteristics of films make them very attractive to be used for MAP of fresh produce such as apple, blueberry and mushroom. Copyright © 2011 John Wiley & Sons, Ltd.     

Hydrophilic modification of silicone elastomer films: Thermal,mechanical and theophylline permeability properties

The improvement of the hydrophilicity of silicone rubber (SR) is sought in many biomedical applications. In the present work, we have prepared neat films coming from condensation-type SR, modified either through blending or end-linking reaction with low molecular weight poly(ethylene glycol) (PEG). The films were studied with respect to their water uptake capacity, stability of embedment of ethylenoxy moieties, and mechanical and thermal properties. Subsequently, we prepared drug-loaded films with theophylline, a relatively hydrophilic model drug, and studied the release performance of these systems. Results on neat films showed that blending increases significantly the overall water uptake of the films and, at the same time, has a limited detrimental effect on their mechanical properties. On the other hand, end-linked films loaded with theophylline exhibited better rate-controlling properties in vitro, due to better dispersion of the sorbed water.     

原子氧环境中聚酰亚胺的质量变化和侵蚀机制

用石英晶体微天平(QCM)原位监测并研究了聚酰亚胺薄膜在地面原子氧模拟装置中暴露时的质量变化.结果表明,聚酰亚胺薄膜在较低的原子氧束流通量暴露的初期,试样的质量先增加后降低,质量的降低与暴露的时间成正比.在高原子氧束流通量暴露的初期,试样质量的增加不明显,甚至一开始就发生稳态氧化失重.实验数据拟合的结果表明,原子氧对聚合物造成的侵蚀主要发生在有氧原子吸附的表面.质量的增加是由于较低的原子氧通量没有能完全氧化聚合物的表面.原子氧对聚合物材料的侵蚀机制服从Langmuir吸附理论.