Detachment Of Film Research Articles

On controlling the anodic electrochemical film deposition of HKUST-1 metal–organic frameworks

Anodic electrochemical synthesis presents itself as a powerful and rapid method to produce porous metal–organic framework (MOF) powders and deposit MOF films onto metal surfaces. Such layers are of interest for adsorptive, catalytic or sensor applications. However, electrochemical MOF synthesis is still in a preliminary stage while a need to better control the process and understand the influences of the process parameters emerges. This work focuses on controlling the deposition of copper-1,3,5-benzenetricarboxylate (HKUST-1, Cu-BTC) MOF layers and targeting different crystal sizes. Moreover, it aims to shed some light on the mechanisms underlying these changes. A number of strategies can be adopted to control the process and adjust the obtained crystal size. By adjusting the synthesis time or water content, the average crystal size can be controlled up to ∼10 μm for ethanol-based synthesis mixtures. The potential also has a pronounced effect, yet a suitable operation window must first be determined to avoid incomplete film formation or excessive film detachment. Furthermore, the influence of the solvent composition on the deposited film morphologies was investigated for mixtures of water, methanol, ethanol, 2-propanol, acetonitrile, N,N-dimethylformamide and dimethylsulfoxide.

Effect of Deposition Time on the Photoelectrochemical Properties of Cupric Oxide Thin Films Synthesized via Electrodeposition Method

The main aim of this study was to investigate the effect of deposition time on the physicochemical and photoelectrochemical properties of cupric oxide (CuO) thin films synthesized via electrodeposition method. Firstly, the electrodeposition of amorphous CuO films on fluorine-doped tin oxide (FTO) working electrodes with varying deposition time between 5 and 30 min was carried out, followed by annealing treatment at 500 °C. Resultant nanocrystalline CuO thin films were characterised using field emission-scanning electron microscopy (FE-SEM), photocurrent density, and photoluminescence measurements. Through FE-SEM analysis, it was observed that the surface of thin films was composed of irregular-sized CuO nanocrystals. A smaller CuO nanocrystals size will lead to a higher photoactivity due to the increase in overall catalytic surface area. In addition, the smaller CuO nanocrystals size will prolongs the electron-hole recombination rate due to the increase in copious amount of surface defects. From this study, it was revealed that the relationship between deposition time and CuO film thickness was non-linear. This could be due to the detachment of CuO thin films from the FTO surface at an increasing amount of CuO mass being deposited. It was observed that the amount of light absorbed by CuO thin films increased with film thickness until a certain extent whereby, any further increase in the film thickness will result in a reduction of light photon penetration. Therefore, the CuO nanocrystals size and film thickness have to be compromised in order to yield a higher catalytic surface area and a lower rate of surface charge recombination. Finally, it was found that the deposition time of 15 min resulted in an average CuO nanocrystals size of 73.7 nm, optimum film thickness of 0.73 μm, and corresponding photocurrent density of 0.23 mA/cm 2 at the potential bias of - 0.3 V (versus Ag/AgCl). The PL spectra for the deposition time of 15 min has the lowest rate of recombination of photogenerated electron-hole pairs by referring to its lowest PL intensity.

Friction behavior of network-structured CNT coating on pure titanium plate

Friction behavior of the network-structured CNTs coated pure Ti plate was evaluated by ball-on-disk wear test using SUS304 ball specimen under dry condition. The friction coefficient was significantly low and stable compared to the as-received Ti plate with no coating film. CNTs coating film had two important roles; self-lubrication and bearing effects to reduce the friction coefficient and carbon solid-solution hardening to improve the abrasive wear property of Ti plate. The annealing treatment at higher temperature (1123K) was more effective to reduce the friction coefficient than that at lower temperature (973K) because the Ti plate surface was uniformly covered with CNTs film even after sliding wear test. This is due to TiC interlayer formation via a reaction between Ti plate and carbon elements originated from CNTs during annealing. As a result, a strong interface bonding between CNTs film and Ti plate surface was obtained by higher temperature annealing treatment, and obstructed the detachment of CNTs film during wear test.

Effect of ZnO films immersion duration in N719 dye on energy conversion efficiency of DSSCs

In this research, ZnO films composed of porous spherical nanoparticles were prepared by a sol–gel method and used to fabricate dye-sensitized solar cells (DSSCs). ZnO films with different thicknesses and different lengths of immersion duration the films in N719 dye were used for solar energy conversion. Among them, the DSSC of ZnO film 5.6–6.2 µm thick immersed in N719 dye for 30 min has the highest performance efficiency. Inappropriate duration for soaking ZnO films in the dye can cause lower efficiency of the DSSCs caused by dye loading, detachment of ZnO films, reduction in number of free electrons, promotion of the recombination process, and transformation of porous films into denser ones.

Temperature-Dependent Fatigue Strength of Diamond Coating-Substrate Interface Quantified via the Shear Failure Stress

A dynamic 3D-finite element method (FEM) thermomechanical model is employed for quantifying the temperature-dependent fatigue strength of nanocrystalline diamond (NCD) coating-substrate interface. This model simulates dynamically the inclined impact test on NCD-coated cemented carbide inserts considering the temperature-dependent residual stresses in the NCD coating structure. A fatigue damage of the NCD coating-substrate interface develops after a certain number of repetitive impacts depending on the applied impact load and temperature. After the interface fatigue failure, the high compressive residual stresses of the NCD coating structure are released, and the detached coating hikes up at a certain maximum height (bulge formation). The critical impact forces for avoiding the fatigue failure of the NCD coating-substrate interface, and the subsequent film detachment after 106 impacts at various temperatures were determined by conducting inclined impact tests up to 400 °C. Considering the critical impact forces, using the mentioned FEM model, the related shear failure stresses in the NCD coating-substrate interface at various temperatures were predicted.

SAM Assisted Nickel-Boron Electroless Metallization of PDMS

Today, rapidly growing range of applications has a critical need for electronic systems, which cannot be made through rigid wafer-based technology. These applications include health-monitoring devices like electrochemical and strain biosensors. The key properties for these devices are bendability and stretchability [1-3]. As intrinsically flexible/stretchable materials have poor electrical performance, the dominant fabrication strategy is to exploit the flexibility of a polymer along with the electrical conductivity of a metal film. In this study, all-wet metallization of polydimethylsiloxane (PDMS) was carried out through Nickel-Boron (NiB) electroless deposition process. Self-assembled monolayers (SAM) of n-(2-aminoethyl) 3-aminopropyl-trimethoxysilane (AEAPTMS) was used to improve the metal thin film adhesion. PDMS surface modification was achieved by sodium hydroxide (1M) immersion for 24h. The modified surface was then silanized by a 0.02% v/v toluene based solution and later activated by a solution of palladium chloride. Water contact angle (WCA) examinations of PDMS surface revealed a significant decrease from 107° for the native surface to less than 50° after surface modification. Surface roughness changes were examined by atomic force microscopy (AFM) before and after each step of surface modification, silanization and metallization. Glow discharge optical emission spectroscopy (GDOES) confirmed the presence of the deposited layers together with the activated interface. Scanning electron microscopy (SEM) observations of PDMS/NiB interface indicated no detachment of NiB film for the silanized samples and significant detachment for non-silanized ones. Results of micro-scratch tests showed a 36% increase in the interface critical normal load of failure for the silanized sample compared to non-silanized one. Samples with three lines of NiB on PDMS (each line with 5mm width and 20mm length) were prepared to act as a flexible electrochemical sensor (Fig. 1). According to cyclic voltammetry results for a scan range of -1 to 1 mV, the presence of 500 and 1000 ppm ethanol in KOH solution (0.5M) were successfully detected. References A. J. Bandodkar, V. W. S. Hung, W. Jia, G. Valdés-Ramírez, J. R. Windmiller, A. G. Martinez, J. Ramírez, G. Chan, K. Kerman and J. Wang. 2013, Analyst., 138, 123.J. T. Muth, D. M. Vogt, R. L. Truby, Y. Mengüç, D. B. Kolesky, R. J. Wood and J. A. Lewis. 2014, Adv. Mater., 26, 6307–6312.W. Jia, A. J. Bandodkar, G. Valdés-Ramírez, J. R. Windmiller, Z. Yang, J. Ramírez, G. Chan and J. Wang. 2013, Anal. Chem., 85 (14), 6553–6560. Figure 1

Compact discs as versatile cost-effective substrates for releasable nanopatterned aluminium films.

We demonstrate that standard polycarbonate compact disk surfaces can provide unique adhesion to Al films that is both strong enough to permit Al film nanopatterning and weak enough to allow easy nanopatterned Al film detachment using Scotch tape. Transferred Al nanohole arrays on Scotch tape exhibit excellent optical and plasmonic performance.

Interfacial Films of Diluted Heavy Oil–Aqueous Systems at Elevated Temperatures and Pressures: Effect of Reverse Emulsion Breakers

Steam-assisted gravity drainage (SAGD) is one of the unconventional methods used in Canada to extract heavy oil; however, a stable water-in-oil-in-water (W/O/W) emulsion is generated during production. The emulsion is then pumped into a high-temperature separator, after adding a diluent, a reverse emulsion breaker (REB), and an emulsion breaker (EB) to separate the oil and water and comply with the sales oil specifications. This work is focused on understanding the demulsification processes under high-temperature (80–120 °C) and high-pressure (700–900 kPa) conditions. Compressibility, crumpling film or drop detachment ratios, and interfacial tension (IFT) were used to evaluate the demulsifiers. REBs were found to decrease IFT and cause the interfacial film to be reversible. These effects showed a dependency with the temperature, and their magnitude varied with the chemistry of the REB. Effective REBs formed complexes with natural anionic surfactants present in the oil phase, weakening the irreversible fil...

Improvement of Thermal Reliability and Power Density of SOFCs By Preparing Nano LSC Particles Between GDC Electrolyte and Lscf Cathode

1.Introduction Solid oxide fuel cells (SOFCs) have received much attention as promising electrochemical power generation devices because of their high electrical efficiency and environment adaptability. Development of SOFCs is now focused on lowering the operating temperature from the conventional range of 750-900°C to an intermediate range of 500-700ºC, allowing a wider range of materials for SOFC components and improvement of thermal reliability. Preparing the Yttlia Stabilized Zirconia (YSZ) and Gadolinia-doped ceria (GDC)) bilayer electrolytes are effective for reducing operating temperature [1]. In the present work, NiO-YSZ anode supported cells with YSZ/GDC bilayer electrolytes and (La,Sr) (Co,Fe) O3 (LSCF) thin film cathodes were fabricated by pulsed laser deposition (PLD) and screen printing. However, one thermal cycle test of a cell between 200°C and 600°C, with heating and cooling rates of 400°C /h, resulted in detachment of the LSCF thin film and thus reduced durability. To improve the adhesion between the LSCF and GDC, (La,Sr)CoO3(LSC), nano particles were deposited on the GDC thin films by PLD. This step was expected to increase contact area between electrolyte and cathode. We investigated the influence of the LSC nano particle on thermal reliability and I-V characteristic of SOFCs. 2.Experimental Details NiO-YSZ cermet (NiO:YSZ＝60:40 wt%, 500 μm thick) was used as the anode substrate, YSZ (8 mol% Y2O3) and GDC (10 mol% GdO2) as electrolyte materials, and La0.6Sr0.4Co0.2Fe0.8 (LSCF) and La0.6Sr0.4Co (LSC) as cathode materials. YSZ (8 μm thick) and LSCF (30 μm thick) films were prepared by screen printing and GDC (3 μm thick) was deposited by PLD. Two sets of unit cells were prepared: one set was with LSC nano particles deposited between GDC and LSCF thin films by PLD (NiO-YSZ / YSZ / GDC / LSC particle / LSCF) and the other set was without LSC nano particles (NiO-YSZ / YSZ / GDC / LSCF).Thermal cycle test between 200 and 600°C with heating and cooling rates of 400° C /h were performed. Power densities and I-V characteristics were measured. 3.Results (a) Deposition of LSC nano particles by PLD on the GDC thin film. Figure 1 shows a scanning electron microscopy image of the surface of a GDC thin film. Many LSC nano particles (50-nm diameter) were deposited on the dense GDC thin film by PLD, which increased the area of contact between the GDC and LSCF thin films. (b) Thermal cycle test of NiO-YSZ anode supported cells with or without LSC nano particles. Two types of unit cells, (1) NiO-YSZ / YSZ / GDC / LSC particle / LSCF and (2) NiO-YSZ / YSZ / GDC / LSCF were prepared by screen printing and PLD. Photographs of unit cells after one thermal cycle are shown in Fig. 2. It is evident that adding the LSC nano particles succeeded in suppressing detachment of the LSCF thin film. Spike effect resulted in high adhesion between LSCF and GDC. The unit cell with LSC nano particles survived 50 thermal cycles and yielded higher thermal reliability. (c) I-V characteristics of NiO-YSZ anode supported cells with or without LSC nano particles. Figure 3 shows the I-V characteristics of unit cells with and without LSC nano particles. The maximum power densities of unit cells with or without LSC nano particles were 0.5 and 0.3 W·cm-2, respectively. Cell performances were found to be better when LSC nano particles were deposited, because of increase in reactive sites.[1] T. Mukai et al., Journal of Fuel Cell Science and Technology , 10(2013) 061006-1-6.

Surface grafted chitosan gels. Part I. Molecular insight into the formation of chitosan and poly(acrylic acid) multilayers.

Composite polyelectrolyte multilayers of chitosan and low molecular weight poly(acrylic acid) (PAA) have been assembled by sequential adsorption as a first step toward building a surface anchored chitosan gel. Silane chemistry was used to graft the first chitosan layer to prevent film detachment and decomposition. The assembly process is characterized by nonlinear growth behavior, with different adsorption kinetics for chitosan and PAA. In situ analysis of the multilayer by means of surface sensitive total internal reflection Raman (TIRR) spectroscopy, combined with target factor analysis of the spectra, provided information regarding composition, including water content, and ionization state of weak acidic and basic groups present in the thin composite film. Low molecular weight PAA, mainly in its protonated form, diffuses into and out of the composite film during adsorption and rinsing steps. The higher molecular weight chitosan shows a similar behavior, although to a much lower extent. Our data demonstrate that the charged monomeric units of chitosan are mainly compensated by carboxylate ions from PAA. Furthermore, the morphology and mechanical properties of the multilayers were investigated in situ using atomic force microscopy operating in PeakForce tapping mode. The multilayer consists of islands that grow in lateral dimension and height during the build-up process, leading to close to exponentially increasing roughness with deposition number. Both diffusion in and out of at least one of the two components (PAA) and the island-like morphology contribute to the nonlinear growth of chitosan/PAA multilayers.

Evolution of lateral ordering in symmetric block copolymer thin films upon rapid thermal processing

This work reports experimental findings about the evolution of lateral ordering of lamellar microdomains in symmetric PS-b-PMMA thin films on featureless substrates. Phase separation and microdomain evolution are explored in a rather wide range of temperatures (190–340 °C) using a rapid thermal processing (RTP) system. The maximum processing temperature that enables the ordering of block copolymers without introducing any significant degradation of macromolecules is identified. The reported results clearly indicate that the range of accessible temperatures in the processing of these self-assembling materials is mainly limited by the thermal instability of the grafted random copolymer layer, which starts to degrade at T > 300 °C, inducing detachment of the block copolymer thin film. For T ⩽ 290 °C, clear dependence of correlation length (ξ) values on temperature is observed. The highest level of lateral order achievable in the current system in a quasi-equilibrium condition was obtained at the upper processing temperature limit after an annealing time as short as 60 s.

An analytical model for droplet separation in vane separators and measurements of grade efficiency and pressure drop

This study investigates the predictive power of analytical models for the droplet separation efficiency of vane separators and compares experimental results of two different vane separator geometries. The ability to predict the separation efficiency of vane separators simplifies their design process, especially when analytical research allows the identification of the most important physical and geometrical parameters and can quantify their contribution. In this paper, an extension of a classical analytical model for separation efficiency is proposed that accounts for the contributions provided by straight wall sections. The extension of the analytical model is benchmarked against experiments performed by Leber (2003) on a single stage straight vane separator. The model is in very reasonable agreement with the experimental values. Results from the analytical model are also compared with experiments performed on a vane separator of simplified geometry (VS-1). The experimental separation efficiencies, computed from the measured liquid mass balances, are significantly below the model predictions, which lie arbitrarily close to unity. This difference is attributed to re-entrainment through film detachment from the last stage of the vane separators. After adjustment for re-entrainment effects, by applying a cut-off filter to the outlet droplet size spectra, the experimental and theoretical outlet Sauter mean diameters show very good agreement. A novel vane separator geometry of patented design (VS-2) is also investigated, comparing experimental results with VS-1. Experimental separation efficiencies based on recorded mass flow balances are very similar for both geometries. However, based on an analysis of the outlet droplet size spectra, VS-2 outperforms VS-1. It is concluded that re-entrainment effects cloud the performance of VS-2 and that the perforations in the wall sections of VS-2 are not very effective. Pressure drop measurements performed on both geometries reveal that the pressure drop for VS-2 is higher than for VS-1 by a factor of almost two for gas velocities up to 10m/s.

Fabrication of Nanoporous Crystalline Alumina Membrane by Anodization of Aluminum

Self-ordered nanoporous α-alumina membrane having uniformly sized straight pore arrays was fabricated by anodization of aluminum and subsequent through-hole and heat treatment. The detachment of thick anodic oxide film formed in oxalic acid was performed by combining preliminary loaded heating before stepwise voltage drop and cathodic polarization in phosphoric acid to prevent excess dissolution at the through-hole process. Suppression of excess dissolution of the upper layer of anodic alumina membrane acted an important role to provide symmetrical evenness of top and bottom pore density for the prevention of deformation such as warp and cracking during subsequent heating for crystallization. Thus, a thick, robust and chemically resistant nanoporous crystalline α-alumina membrane was successfully obtained by optimizing preparation conditions.

Electrostatic damage by detachment of protective film on polarizer

Abstract LCD manufacturing processes are often exposed to the electrostatic hazards due to going through various optic film processes. In this paper, we report the electrostatic discharge failure that occurred during the detachment process of protective film to attach consecutive one on a panel. The effects of modified surface treatment on an adhesive layer of the protective film and the entry sequence of the stage to move the following process in the peeling process of protective film were analyzed. The difference of the respective surface properties of the protective film was investigated using scanning electron microscope (SEM) and the electrostatic voltage measurements during a peeling process. The surface characterization of the film, when it is being rubbed and separated from main film, affects the amount and variation of electrostatic charge generation. Modified surface treatment of a protective film showed significant effect to reduce the failure rate and the maximum friction charge. And it was found that changing solely the entry sequence of the following stage with the modified protective film has a residual electrostatic problem. As a result, a main cause of the failure is considered that the variation of the capacitance between the panel and the stage when charges are generated during a peeling process.

The case study of an Italian contemporary art object: Materials and state of conservation of the painting “Ragazzo seduto” by Remo Brindisi

Abstract This paper deals with the scientific survey of Remo Brindisi's painting “Ragazzo seduto” (Seated boy), made at the end of the 1950s, that is a symbolic figure of both his personal artistic solitude and the crisis of values determined by the economic boom in the post-war period. In a period of great changes and economic regrowth, the need to find a new style that could be the most authentic and personal as possible pressed the artist to experiment innovative products, including non-conventional support. Photographic and analytical techniques demonstrated the use of innovative products as an experimentation tendency, that pressed the artist to use non-conventional support, industrially treated with plasticized PVC and primed with acrylate polymers and to paint with traditional and industrial pigments mixed with an oil-modified alkyd resin. In the span of a few years, an unexpected and extended degradation on the whole surface of the painting took place, with the consequent formation of lifting and detachment of the paint film. The detected alteration is mainly due to the fast ageing of the employed polymeric materials, actually responsible of the impermanence of many contemporary works of arts. Clarifying the unknown aspects of the Remo Brindisi's stylistic choices together with the deterioration processes of the employed painting materials, this paper highlights the general problems related to the conservation of contemporary art, a neglected area of research in Italy, where more efforts are committed to the enormous and more ancient cultural heritage.

Nanomechanical mapping of graphene layers and interfaces in suspended graphene nanostructures grown via carbon diffusion

Graphene's remarkable mechanical, electronic and thermal properties are strongly determined by both the mechanism of its growth and its interaction with the underlying substrate. Evidently, in order to explore the fundamentals of these mechanisms, efficient nanoscale methods that enable observation of features hidden underneath the immediate surface are needed. In this paper we use nanomechanical mapping via ultrasonic force microscopy that employs MHz frequency range ultrasonic vibrations and allows the observation of surface composition and subsurface interfaces with nanoscale resolution, to elucidate the morphology of few layer graphene (FLG) films produced via a recently reported method of carbon diffusion growth (CDG) on platinum-metal based substrate. CDG is known to result in FLG suspended over large areas, which could be of high importance for graphene transfer and applications where a standalone graphene film is required. This study directly reveals the detailed mechanism of CDG three-dimensional growth and FLG film detachment, directly linking the level of graphene decoupling with variations of the substrate temperature during the annealing phase of growth. We also show that graphene initially and preferentially decouples at the substrate grain boundaries, likely due to its negative expansion coefficient at cooling, forming characteristic “nano-domes” at the intersections of the grain boundaries. Furthermore, quantitative nanomechanical mapping of flexural stiffness of suspended FLG “nano-domes” using kHz frequency range force modulation microscopy uncovers the progression of “nano-dome” stiffness from single to bi-modal distribution as CDG growth progresses, suggesting growth instability at advanced CDG stages.

Adhesion of Elastic Thin Films: Double Peeling of Tapes Versus Axisymmetric Peeling of Membranes

The mechanism of detachment of thin films from a flat smooth rigid substrate is investigated. In particular, analytical solutions in closed form are proposed for the double peeling of an elastic tape as well as for the axisymmetric peeling of a membrane. We show that in the case of double peeling of an endless elastic tape, a critical value of the pull-off force is found, above which the tape is completely detached from the substrate. In particular, as the detachment process advances, the peeling angle is stabilized on a limiting value, which only depends on the geometry of the tape, its elastic modulus and on the interfacial energy $$\Updelta\gamma$$ . This predicted behavior agrees with the “theory of multiple peeling” and clarifies some aspects of this theory. Moreover, it is also corroborated by experimental results (work in progress) we are carrying out on a standard adhesive tape adhered to a smooth flat poly(methyl methacrylate) surface. In the case of the axisymmetric adhering membrane, a different behavior is observed. In such case, the system is always stable, and the detached area monotonically increases with the peeling force, i.e., the elastic membrane can sustain in principle any applied force. Results are validated by a fully numerical analysis performed with the aid of a finite element commercial software.

Hydrogen microscopy – Distribution of hydrogen in buckled niobium hydrogen thin films

Hydrogen absorption in thin metal films clamped to rigid substrates results in mechanical stress that changes the hydrogen's chemical potential by ΔμH(σ) = −1.124σ kJ/molH for σ measured in [GPa]. In this paper we show that local stress relaxation by the detachment of niobium hydrogen thin films from the substrate affects the chemical potential on the local scale: using coincident proton–proton scattering at a proton microprobe, the hydrogen concentration is determined with μm resolution, revealing that hydrogen is not homogenously distributed in the film. The local hydrogen solubility of the film changes with its local stress state, mapping the buckled film fraction. In niobium hydrogen thin films loaded up to nominal concentrations in the two-phase coexistence region, the clamped film fraction remains in the solid solution phase, while the buckles represent the hydride phase. These results are compared to a simple model taking the stress impact on the chemical potential into account.

Surface Modification by Atmospheric Pressure DBDs Plasma: Application to Electroless Ni Plating on ABS Plates

Acrylonitrile-butadiene-styrene (ABS) plastic is a polymer material extensively used in electrical and electronic applications. Nickel (Ni) thin film was deposited on ABS by electroless plating, after its surface was treated and modified with atmospheric plasma generated by means of dielectric barrier discharges (DBDs) in air. The method in this study was developed as a pre-treatment for electroless plating using DBDs, and is a dry process featuring fewer processing steps and more environmentally friendliness than the chemical method. After ABS surfaces were modified, surface morphologies were observed using a scanning electron microscope (SEM) to check for any physical changes of the surfaces. Cross-sectional SEM images were taken to observe the binding characteristics between metallic films and ABS after metal plating. According to the SEM images, the depths of ABS by plasma are shallow compared to those modified by chemically treatment. The static contact angles were measured with deionized (DI) water droplets on the modified surfaces in order to observe for any changes in chemical activities and wettability. The surfaces modified by plasma showed smaller contact angles, and their modified states lasted longer than those modified by chemical etching. Adhesion strengths were measured using 3M tape (3M 810D standard) and by 90° peel-off tests. The peel-off test revealed the stronger adhesion of the Ni films on the plasma-modified surfaces than on the chemically modified surfaces. Thermal shock test was performed by changing the temperature drastically to see if any detachment of Ni film from ABS would occur due to the differences in thermal expansion coefficients between them. Only for the plasma-treated samples showed no separation of the Ni films from the ABS surfaces in tests. The adhesion strengths of metallic films on the ABS processed by the method developed in this study are better than those of the chemically processed films.

Stability of polydopamine and poly(DOPA) melanin-like films on the surface of polymer membranes under strongly acidic and alkaline conditions

This study investigated the stability of polydopamine and poly(3,4-dihydroxyphenylalanine) (poly(DOPA)) melanin-like films on the surface of polymer substrates. Three polymer membranes, polypropylene (PP), poly(vinylidenefluoride) (PVDF) and nylon, were modified with polydopamine or poly(DOPA), and then immersed in 0.1M HCl or NaOH, followed by UV–vis spectrometry analysis to detect the presence of film detachment. The results showed that the outer parts of both polydopamine and poly(DOPA) films were detached, probably due to electrostatic repulsion between the polymers within the film, when the modified membranes were washed in HCl or NaOH solution. These two films were more stable in strongly acidic solution, but the stability of poly(DOPA) film was better than that of polydopamine film. Compared to the films on the surface of PVDF or nylon membrane, films on PP surface showed the lowest stability, possibly because of the hydrophobic property of PP. The process of film detachment was analyzed by GPC, which showed that unreacted dopamine or DOPA monomers were still present in the freshly formed films. The unreacted monomers, as well as polydopamine or poly(DOPA) that were incorporated in the film via noncovalent interactions, became detached when the film was exposed to strongly acidic or alkaline solution. Oxidation of freshly formed films could significantly enhance their stability. The results therefore provide us with a better understanding of the stability of melanin-like films, and allow us to develop an effective strategy for constructing stable films.