PAA Films Research Articles

A multi-strategy coating for Al alloy based on orientationally arranged nanosheets doped SiO2 coating and corrosion inhibitor loaded porous anodic alumina film

Although aluminum alloys are widely used in various industries, their wear and corrosion resistance are still needed to be enhanced. In this study, a robust anti-corrosion composite coating was prepared on the surface of Al alloy based on multiple reinforcement strategies. The composite coating is consisted of horizontally arranged and functionally modified h-BN nanosheets doped SiO2 coating (SiO2-hBN(NH3+) coating) and corrosion inhibitor MBT loaded porous anodic alumina (PAA-MBT) film. Results show that the composite coating prepared in this work has excellent corrosion resistance due to the effect of the extended penetration path of corrosive medium by h-BN(NH3+) nanosheets, the full-thickness hydrophobicity of the SiO2 coating, the corrosion inhibition of the MBT released from the PAA film and the physical barrier of the entire coating system. In addition, the composite coating also exhibits good mechanical properties including high hardness, high bonding strength and superior wear resistance. This work provides a novel design of protective coating with excellent anti-corrosion resistance and mechanical properties, which has a promising prospect in the development of superior long-term anti-corrosion coatings for aluminum alloy.

Moisture Absorbing and Water Self‐Releasing from Hybrid Hydrogel Desiccants

AbstractAtmospheric moisture is a valuable resource for fresh water and potentially sustainable energy. However, direct harvesting water from moisture (the vapor form) remains the most challenging. Hybrid desiccants made from hydrogels embedded with salt offer promise in absorbing moisture. However, the desorption process often requires additional energy to heat the samples. Here, poly(acrylic acid) (PAA) hydrogels embedded with lithium chloride are prepared, demonstratng simultaneous moisture absorption and self‐release of liquid water at room temperature with 50–90% relative humidity. The water self‐releasing process can be separated into two distinct stages: 1) surface release, where water droplets grow on the hydrogel surface due to differences in nucleation and diffusion rates, and 2) bulk release, triggered by the collapse of polymer chains, subsequently releasing water from the hydrogel network. Factors such as salt concentration, hydrogel crosslinking density, and film thickness are investigated to better understand the moisture absorption and water‐releasing processes. Moreover, hydrophobic domains are introduced onto the salt‐embedded PAA films, creating an edge effect that enhances the droplet growth rates. When the hydrophobic domains are patterned, the movement of released water can be guided, resulting in a threefold increase in water removal rate attributed to gravitational force.

Organic mixed ion-electron conductive composite films based on polyacrylic acid/polyaniline

Composite materials of polyacrylic acid complexed with polyaniline (PAA/PANI) can be used to form organic mixed ion-electron conductive (OMIEC) films. These are promising candidates for next-generation optoelectronic and energy storage applications. PAA/PANI composite films are connected by blending the amine (NH) groups in PANI with carboxylic groups (COOH) in PAA by an acid-base reaction via strong electrostatic interactions with intermolecular hydrogen bonds. PAA/PANI composite films show that a PAA-rich matrix separates PANI-rich domains. The electrical conductivity of pure PAA film is 0.58 mS cm−1, which is attributed to negatively charged COO− groups, allowing for ion transfer inside the polyelectrolyte. The electrical conductivity of PANI film is 3.56 mS cm−1, which is attributed to the weakly bound electron conductions of the polaron states along delocalized π-orbitals. PAA/PANI composite films with 33 wt% of PANI have higher electrical conductivity (6.57 mS cm−1) due to the high ionic-electronic coupling through the polymer matrix at the interface between phase-separated regions.

Influence of oxalic additive on etidronic acid anodizing of aluminum alloy

The anodizing in etidronic acid (HEDP) and oxalic acid (H2C2O4) mixed electrolytes was conducted. The anodizing parameters were optimized based on the evaluation of energy consumption, growth efficiency, and hardness of PAA film. The results indicate that continuous and uniform PAA films can be fabricated in HEDP/H2C2O4 solutions in any proportion, and both the anodizing voltages and roughnesses of PAA films decreased with the H2C2O4 content. The moderate amount of H2C2O4 could lead to an increase in the formation efficiency of PAA films. The hardness of the PAA film prepared in HEDP/H2C2O4 electrolyte could reach up to ∼660 HV. Moreover, a surface resembling lotus leaves could be formed due to the corrosion of PAA films with sub-micron interpore distance by H2C2O4 during anodizing, and a superhydrophobic surface with a contact angle of ∼153° could be obtained after it was modified via stearic acid.

Water-Absorbing Bioadhesive Poly(Acrylic Acid)/Polyvinylpyrrolidone Complex Sponge for Hemostatic Agents.

Poly(acrylic acid) (PAA) is a water-soluble synthetic polymer with tissue-adhesive properties. When PAA is mixed with polyvinylpyrrolidone (PVP) in water, it forms a water-insoluble precipitate that neither swells nor adheres to tissues. We developed a novel solid/solution interface complexation method to obtain a water-swellable PAA/PVP complex. First, PAA solution was dried up in a vessel to form a film. The PAA film was then immersed in an aqueous PVP solution to obtain a highly swollen PAA/PVP hydrogel. Heat drying of the hydrogel yielded a transparent film, while freeze-drying the hydrogel provided a soft sponge. Both the PAA/PVP film and sponge could be re-swelled by water to obtain a bioadhesive gel. A relatively larger specific surface area of the sponge than that of the film led to a more rapid swelling and water absorption behavior and quick adhesion to tissues. The addition of hyaluronic acid (HA) improved the mechanical characteristics of the sponges. PAA/PVP/HA sponges had low cytotoxicity, and they exhibited high hemostatic efficiency in clinical studies after dialysis treatment or tooth extraction, even in patients on antithrombotic drugs. Such bioadhesive materials consisting of low-toxicity polymers have a high potential for use in medical hemostatic devices.

Vapor Deposition of Transparent Antifogging Polymeric Nanocoatings.

This study demonstrates the coating of a transparent and robust organic thin film having an excellent hydrophilicity-based antifogging property by an initiated chemical vapor deposition (iCVD) method. iCVD was able to synthesize linear and cross-liked poly(acrylic acid) (PAA) from the vapors of acrylic acid (AA) and ethylene glycol dimethacrylate (EGDMA) using tert-butyl peroxide (TBPO) as an initiator. High deposition rates of up to 35 nm/min were observed at low deposition temperatures. It was possible to control the quantity of comonomers in the as-deposited films by adjusting the partial pressure of the EGDMA cross-linking agent. The effect of the EGDMA partial pressure on chemical structure was studied using Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) techniques. FTIR and XPS spectra of the as-deposited films showed the complete retention of the monomer functionality during iCVD. Hydrophilicities and large-area uniformity of the coatings were revealed using water contact angle measurements. The as-deposited PAA film was the most hydrophilic with a water contact angle (WCA) of 7.0°, while cross-linking with EGDMA increased the WCA values by up to 51.7°. Results of various tests, which were based on exposing the coated surfaces to artificial fog and hot water vapor, showed the excellent antifogging property of the coatings. Films were never fogged upon extensive and long-term exposure (2 months) to humid air.

Effect of hydrothermal treatment on porous anodic alumina generated by one-step anodization

Abstract The effects of the hydrous oxide film obtained from the hydrothermal treatment of the electropolished aluminum sheet on the porous anodic alumina produced by the first step of anodization in oxalic acid were investigated. It is indicated that the dense barrier layer within the hydrous oxide film can bring about a nearly exponential decrease of the current as a function of time. As to the porous layer of the hydrous oxide film, namely the ‘cornflake’ structure onto the barrier layer, it can optimize the initially nucleated site of the nanoporous during the anodization, which is beneficial to the self-ordered array of the nanoporous generated on the PAA film. It is concluded that the hydrous oxide film produced by the hydrothermal treatment can facilitate the self-assembly of the porous anodic alumina even if the applied potential is 60 V in oxalic acid.

2D infrared correlation study of the effect of base catalyst on thermal imidization of polyamic acid

The thermally induced structural changes of 6FDA-ODA PAA films in the presence and absence of a base catalyst, 2,6-dimethyl piperidine, were investigated using in situ FTIR spectroscopy. In addition, principal component analysis (PCA) and 2D correlation spectroscopy (2D-COS) were applied to clarify the thermal imidization behaviors. Based on the PCA results, we can confirm the various products formed during thermal imidization. The results of 2D correlation analysis revealed the thermally induced changes in the spectra of the 6FDA-ODA PAA films. In addition, we propose that the thermal imidization of the 6FDA-ODA PAA film in the presence of a base catalyst, 2,6-diemthyl piperidine, starts at a lower temperature than it does in the absence of a base catalyst.

Functionalization of MWNTs and its Influence on Thermal Performance of Modified Diphenyl Ether Polyimide Films

In this paper, we treated MWNTs by Fendon oxidation method and mixed acid method, finding the factors of functionalized effect affecting MWNTs. And added MWNTs treated to PI matrix for the study of the impact of MWNTs treated on thermal properties of the films. We using 3,3/,4,4/-diphenyl ether tetraacid dianhydride (ODPA) and 4,4'-diamino diphenyl ether (ODA) as raw material, mixing functional MWNTs and monomer by situ polymerization, then MWNTs / PAA hybrid glue was prepared. The molecular weight and distribution of the polyamic acid were measured by gel permeation chromatography (GPC), and the effects of different addition amounts on the product were examined. The PI/MWNTs films were prepared using an automatic film applicator, and finally the PI films were obtained by thermal imidization. The thermal behavior of the imidization process of the product was determined by differential scanning calorimetry (DSC) and thermogravimetric analysis (TG). The results showed that the PAA film has thermodynamic behavior at 150 ° C and 280 ° C approximately, which could be regarded as the kinetic interruption temperature of the imidization reaction. The dehydration cyclization reaction mainly occured in these two temperature ranges, moreover, the addition of MWNTs had no significant effect on the thermal decomposition temperature of the material which doping amount that does not affect the mechanical strength.

Application of SERS active substrate prepared by nanotechnology in ophthalmic care

The application of nanomaterials in ocular drug delivery is mainly concentrated in nano-controlled release systems. Due to the unique properties of nanomaterials, the use of nanomaterials to carry drugs for treating eye diseases has great advantages compared with traditional drug delivery methods. The nano-formulation of the drug has higher bioavailability and lower side effects. Therefore, the nano-controlled release system has a good application prospect in ophthalmology. In this paper, Fe2O3 magnetic nanoparticles were first prepared by co-deposition, and then the nanoparticles were clad with silica to prepare Fe2O3 @SiO2 core-shell nanostructures. Secondly, an ordered array surface-enhanced Raman scattering (SERS) active substrate was formed on the surface of the porous layer of porous anode aluminium oxide (PAA) and the barrier layer using vacuum electron beam evaporation technology using PAA films as templates. Then, the shell thickness of Fe2O3@SiO2 and the number of coated magnetic particles were controlled by controlling the dosage of ethyl orthosilicate, and a layer of SERS active gold nanoshells was grown after further adsorption of gold seeds to prepare a composite SERS active substrate. Enhanced performance magnetic nanomaterial Fe2O3@SiO2@PAA @Au. Finally, the SERS spectrum and fluorescence quenching characteristics of ocular cells adsorbed on the substrate were detected and analysed. The results show that the magnetic nanomaterial Fe2O3@SiO2@PAA @Au with enhanced performance of SERS active substrate has a good enhancement effect on the Raman scattering signal of eye cells, and to a certain extent, it can eliminate the interference of the fluorescent background. Moreover, the ordered array of SERS active substrates not only has a high SERS enhancement ability and ability to quench fluorescence, but also does not have interference peaks of oxalate impurities remaining in the PAA film, which can obtain more detailed information of the Raman scattering spectrum of eye cells to achieve eye care.

Bioinspired hierarchical cross-linked graphene-silicon nanofilms via synergistic interfacial interactions as integrated negative electrodes for high-performance lithium storage.

Inspired by the intrinsic relationship between sophisticated interfacial architecture and the outstanding mechanical performance of natural nacre, a flexible, large-area and robust bioinspired reduced graphene oxide-silicon-carboxymethyl cellulose-polyacrylic acid (rGO-Si-CMC-PAA) nanocomposite film with a hierarchically laminated structure was prepared via a vacuum-assisted filtration self-assembly process and a thermal condensation reaction. The as-prepared rGO-Si-CMC-PAA films exhibited a typical orderly layered structure with a thickness of about 40 μm, and Si nanoparticles were uniformly distributed and embedded throughout the continuous graphene network. As binder-free, integrated anodes for lithium-ion batteries (LIBs), the free-standing rGO-Si-CMC-PAA films exhibited appealing electrochemical lithium storage properties with a high reversible capacity (2153.49 mA h g-1), long-term cycling stability with 63% capacity retention even after 800 cycles at 420 mA g-1, and a superior rate capability. Therefore, the bioinspired strategy of synergistic interfacial interactions of hydrogen and covalent bonding also provides a promising avenue for constructing integrated high-performance graphene-based nanocomposite films in the future.

Transfer printing via a PAA sacrificial layer for wrinkle-free PDMS metallization

Polydimethylsiloxane (PDMS) metallization has been extensively used in varieties of micro- and nanosystem technologies. However, the deposited metal film on the PDMS surface is prone to wrinkling because of a large thermal mismatch stress, which may cause difficulties in some applications. In this work, a simple transfer printing method via a poly(acrylic acid) (PAA) sacrificial layer for PDMS metallization is presented. A PAA film was spin-coated on the silicon substrate, metal patterns were fabricated on the PAA film based on photolithography techniques, and a PDMS sheet was put on the surface of metal patterns and separated with metal patterns from the silicon substrate by dissolving the PAA film in room-temperature water. Au patterns with a variety of shapes and sizes were successfully transferred on the PDMS sheet, and there were no wrinkles in Au patterns. As a demonstration, a PDMS-based tunable diffraction grating with a line width of 2 µm and an initial period of 4 µm was fabricated. The grating displayed excellent diffraction efficiencies, and the period could be tuned by simply stretching the grating.

Thermal imidization behaviors of 6FDA-ODA poly(amic acid) containing curing accelerators by in-situ FTIR spectroscopy

In-situ FTIR spectroscopic measurements were used to examine the thermal imidization behaviors of 6FDA-ODA PAA films in the presence of a strong tertiary amine base, such as piperazine, N,N’-dimethyl piperazine, piperidine, and 2,6-dimethyl piperidine. Large spectral changes in the FTIR spectra of 6FDA-ODA PAA films in the presence of curing accelerators were observed in the range of 110∼190 ℃, and strong tertiary amine bases used in this study accelerate the imidization reaction. Less sterically hindered piperidine with a strong base strength led to a relatively slow imidization reaction compared to piperazine, N,N’-dimethyl piperazine, and 2,6’-dimethyl piperidine. N,N’-dimethyl piperazine and 2,6-dimethyl piperidine are effective curing accelerators similar to piperazine.

Rapid and In Situ Synthesis of Gold Nanoparticles in Redox Multilayer Film for Biosensor Applications

AbstractFerrocene‐grafted poly(ethyleneimine)/poly(acrylic acid) (PEI‐Fc/PAA) multilayer films were constructed via layer‐by‐layer assembly. When the PEI‐Fc/PAA films were immersed in HAuCl4 solution, Fc and the AuIII were converted to Fc+ and Au0, respectively, via the redox reaction of Fc and HAuCl4, and the PEI‐Fc/PAA@Au nanoparticles (NPs) multilayer films were rapidly fabricated. SEM and TEM results showed Au NPs were distributed homogeneously throughout the thickness of the whole film. The electron transfer behavior of PEI‐Fc/PAA@Au NPs multilayer films was investigated by cyclic voltammetry and AC impedance. The results indicated that the Au NPs greatly improve the conductivity of multilayer films and thus enhance the electrochemical properties of films. The PEI‐Fc/PAA@Au NPs films were further used for the fabrication of a hydrogen peroxide (H2O2) sensor, which showed good catalytic ability for the reduction of H2O2. This approach is expected to expand the routes towards rapid fabrication of Au NPs into multilayer films.

Thermal degradation of peat-based activated carbons covered with mixed adsorption layers of PAA polymer and SDS surfactant

The thermal behaviour of activated carbons obtained from peat and modified with poly(acrylic acid) - PAA films was examined. Additionally, the effect of anionic surfactant – sodium dodecyl sulfate (SDS) presence in the adsorption layer was determined. Three samples of activated carbons were analyzed: (1) sample N - obtained by pyrolysis of peat followed by steam activation, (2) sample N9C - obtained by physical activation of sample N with carbon dioxide and (3) sample N9K - obtained by chemical activation of sample N with potassium carbonate. TG, DTG and DSC coupled with FTIR and QMS spectrometry enable not only specification of thermal stability of examined systems, but also determination of main gaseous products of their thermal decomposition. The obtained results indicate that polymer/surfactant adsorption influences significantly the thermal degradation of used carbon materials.

Crosslinkable-Chitosan-Enabled Moisture-Resistant Multilayer Gas Barrier Thin Film.

Chitosan-based films exhibit good oxygen barrier that degrades when exposed to high humidity. In an effort to overcome this drawback, a multilayer nanocoating consisting of crosslinkable chitosan (CHQ) and poly(acrylic acid) [PAA] is deposited on polyethylene terephthalate (PET) using layer-by-layer assembly. Chitosan is functionalized with glycidyl methacrylate to introduce acrylic functionalities within the film. The deposited films are crosslinked using a free radical initiator and this crosslinking is confirmed by FTIR and reduced film thickness. A 10-bilayer (BL) crosslinked CHQ/PAA film, which is only 165nm thick, results in a 36× reduction of the oxygen transmission rate of PET at 90% relative humidity. To achieve these same results without crosslinking, a 15-BL unmodified chitosan (CH)/PAA film, which is almost 5× thicker, must be deposited on PET. This environmentally friendly, transparent nanocoating is promising for food packaging or protection of flexible electronics, especially in high-humidity environments.

Preparation of polyacrylic acid-grafted-acryloyl/hemicellulose (PAA-g-AH) hybrid films with high oxygen barrier performance

Developing high-performance oxygen barrier films using biomass-based materials is crucial for the development of green and sustainable society. Herein, we develop a strategy to synthesize polyacrylic acid-grafted-acryloyl/hemicellulose composites (PAA-g-AH) as film materials with excellent oxygen barrier property. The as-synthesized films were extensively characterized by Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), gel permeation chromatography (GPC), 1H nuclear magnetic resonance (1H NMR), mechanical test, light transmittance and oxygen transmission rate (OTR) measurement. All these testing results showed that the optimum film exhibit great oxygen barrier property with a low OTR value of 0.25 ± 0.01 cm3* μm/(m2*d*kPa), which was much lower than that of pure PAA film. Moreover, the hybrid films possess well mechanical strength, light transmittance and recycle usage properties. Experimental results indicated that the as-synthesized films have great potential applications in several fields as packaging materials, such as drug, food and electronic products.

Effect of heat treatment on the tribological behaviors of polyelectrolyte/Au nanoparticles composite films

Abstract PAH/Au/PAH/PAA film was prepared by the layer-by-layer (LbL) method. AFM and micro-tribometer were used to evaluate the frictional and wear behaviors of the film. The result indicated that heat treatment can improve the bonding force of the film because of the conversion from electrostatic interaction to covalent bond. Which greatly enhanced the film's anti-wear life. However, the film surface's roughness increases dramatically and uniformity decreases with longer heating time. Which would influence the friction and wear performance of the film. Thus, the heating time is a critical parameter in the prospect of improving the film layers bonding strength, consequently enhancing the wear-resistant of the polyelectrolyte/Au nanoparticles multilayer film.

Supramolecular layer: Toward resolving the conflict between rigidity and flexibility in design of pressure-enhanced luminescence molecule

The design of pressure-related aggregation-induced emission (PAIE) molecular structure has to find a compromise between rigidity and flexibility. In order to resolve the contradiction, here a supramolecular layer is constructed by employing three components containing 1,2-bis[4-(3-sulfonatopropoxyl)-phenyl]-1,2-diphenylethene sodium salt (BSTPE), layered double hydroxides (LDHs) and poly(acrylic acid) (PAA). Mechanism shows: 1) rigid LDH nanosheet not only can avoid interpenetration between adjacent layers of PAA films, but assistants the formation of aggregation-induced emission (AIE) molecular layer; 2) PAA can wrap the BSTPE molecules and provide sufficient free space for rearrangement of AIE molecules during the pressure response owing to its high flexibility. The as-constructed (BSTPE@PAA/LDH)n supramolecular layer film shows an excellent anisotropic structure and emission performances, accompanied by high stability (photo, adhesion and storage). Interestingly, the pressure-related luminescence behavior of the film at the MPa level. The gradually increased intensity with the increase of pressure is attributed to the tight and order packing of BSTPE in interlayer of LDHs by the external pressure. This work provides a design rule for the construction of pressure-sensitive supramolecular layer, which resolves the conflict between rigidity and flexibility in the molecule design of pressure-enhanced emission materials.

Optimal sampling and reconstruction of undersampled atomic force microscope images using compressive sensing

Atomic force microscope (AFM) is an analytical instrument which is used to study the surface structure and morphology of materials. The AFM can measure and observe samples either in air or liquid environment. However, the standard AFM requires a long time to acquire accurate images and data. In our work, the compressive sensing (CS) was applied in order to reduce the imaging time, lower the interactions between the probe and the sample, finally avoid sample damage in AFM. Three samples (PAA film, TGG1 grating and BOPP film) were used as the testing samples. Different image reconstruction algorithms (l1-ls, TVAL3, GPSR and IHT) were employed to reconstruct AFM image with different sampling rate. And various sampling patterns (Random Scan, Row Scan, SRM, Spiral Scan and Square-shape Scan) were used to obtain the undersampling data. A large number of experiments show that the choice of sampling pattern and image reconstruction algorithm has significant impact on the quality of the reconstructed images in AFM. Subsequently the reconstruction results of sample topographic images were analyzed and evaluated by the image quality indicators (PSNR and SSIM). The CS method can be used to obtain accurate images by reducing measurement data. It finally improves the measurement speed of AFM without cutting down the quality of AFM image.