Polyimide surface ordering

Previous studies have shown that a trend exists in the behavior of some evaporated metals on polyimide surfaces x-ray and ultraviolet photoelectron (XPS, UPS) as well as high resolution electron energy loss (HREELS) measurements have indicated that while for some metals such as aluminum, titanium and chromium there is bond formation with the PMDA carbonyl oxygen of the polyimide (2, 10-13). other metals such as copper, palladium and gold undergo little reaction or interaction (10,12,14,15). It has, however, since been postulated that metals, in order to adhere well at all to a polymer under a wide variety of conditions, must form metal- polymer bonds (10). 

To explain the phenomenon of decomposition, Hasegawa applied the reaction kinetic model [20]. The peak value of the order parameter of the LC mixture attached to the polyimide surface was achieved at an exposure energy of about 1 J/cm and fitted the experimental data well (Figure 2.16). 

As stated, the capability of plasma deposits to reduce the access of water to corrosion-sensitive surfaces may be an important motivation for their application in corrosion protection. In order to study this property, Kapton polyimide film was selected as the substrate because of its high inherent permeability to water and its ability to resist elevated temperatures. The response of Kapton film overcoated by PPHMDSO to the permeation of water vapor is shown in Fig. 1. Clearly, the presence of the organo-silicone plasma film greatly reduces water permeation. The magnitude of the effect is much enhanced when plasma polymers are produced at high T and p. 

Much of the recent wor)c pertaining to metal ion modified polyimides has been aimed at increasing the surface electrical conductivity of condensation polyimides (6,7,8). This has been accomplished to a significant extent (surface resistivity reduced up to 11 orders of magnitude (8,9)) but in most systems the bul)c... 

The air-side resistivity of the cobalt chloride modified polyimide film was Increased to the value observed with a nonmodified BTDA-ODA polyimide film while, the cobalt chloride modified BDSDA-ODA polyimide film had an increase in surface resistivity of only about three orders of magnitude after soa)cing this film in water. The variable temperature air-side surface resistivity profiles for the cobalt chloride modified BDSDA-ODA polyimide film before and after a water soa)c are shown in Figure 4. 

The structural anisotropy in crystalline or structurally ordered BPDA-PFMB films was studied in this laboratory with wide-angle X-ray diffraction (WAXD) methods. In brief, WAXD experiments were designed to examine both the reflection and transmission modes of thin-fihn samples. In addition, uniaxially oriented polyimide fiber WAXD patterns were obtained to aid in the identification of the film structure. The film WAXD pattern obtained from the reflection mode corresponded well to the fiber pattern scanned along the equatorial direction (Figure 16.3), " which indicates that the reflection mode pattern represents the (hkQ) diffractions. On the other hand, as shown in Figure 16.4, the (001) diffractions were predominant in the film WAXD pattern obtained via the transmission mode. This pattern corresponded to the fiber pattern scanned along the meridian direction. These experimental observations clearly indicate that the c-axes of the crystals are preferentially oriented parallel to the film surface however, within the film, they are randomly oriented. 4.2 5 j( should be pointed out that the WAXD experiments are only sensitive to crystalline or ordered structures in polyimide films. They do not provide any information on the amorphous regions. 

In order to demonstrate the performance of this electrochemical microimmunoassay platform in terms of limits of detection and dynamic range, a series of ALP tests has been conducted in 100 nL polyimide microchips. To this end, anti-phosphatase antibodies have first been immobilised on the surface of the microchannels at a concentration of 10 pg/mL in a flow-through mode (4mL of anti-ALP solution pumped at 0.4 mL/min during 10 min) so as to saturate the microchannel surface by physical adsorption. Then, the surface was blocked with a 5% BSA in phosphate buffer in order to block the free sites remaining on the surface. Solutions of ALP at various concentrations (namely 0, 0.1, 1, 10 and 100 pM) were then injected and incubated during 9 min in the... 

Although the mechanisms of polyimide/metal adhesion remain to be fundamentally elucidated, it is generally accepted that the interfacial diffusion of metallic entities into the polyamic acid plays a key role at the interface [156-158]. Two main theories have been reported explaining the adhesion of the Pl/metal bond chemical and mechanical bonding [159]. Initial work emphasized mechanical bonding and most efforts were dedicated to the physical roughening of the substrate by different abrasive methods as well as chemical treatments in order to improve metal to polyimide adhesion by increasing the metal surface area [156,160-164]. 

It is therefore understandable that the first HREELS measurements were performed on Langmuir-Blodgett ordered layers, thin polyimide films and conducting polymers (2). Nowadays, almost any polymer surface could be analyzed with HREELS. 

In this work, we present the effect of 193 nm pulsed UV high intensity radiation on polyimide, a polymer well known for its applications in solid-state technology (thermal stability and dielectric properties). We have used XPS in order to determine the evolution of chemical surface composition versus laser fluence and have obtained some attractive informations about these modifications induced by UV laser radiation. 

From all these XPS informations in order to take into account the fact that after the laser treatments several species like isoimide, C=N-,-CO,0-C-0, and carboxylic groups are present at the surface of polyimide, we propose the following surface reaction under UV laser radiation above the ablation threshold in presence of air moisture ... 

The surface of the polyimide film of was observed by SEM to be as flat as that of The multilayer film of was prepared on a silicon wafer which contained evaporated aluminum lines in order to examine the coating ability of the present LB films. Figure 3(a) exhibits the mechanical stylus probe (Talystep) pattern of aluminum lines (30 nm high and 2000 nm wide) and (b) shows the lines after 120 layers of were deposited. Since the depth was observed as 30 nm in both cases, it is concluded that the multilayer film can conformally coat the uneven surface. This feature can be directly observed in the photographs of Figure 4 where a 60 layer film of is coated on an aluminum line (200 nm of high and 2000 nm wide). 

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