Poly Acrylic Acid Films Research Articles

Improving stability of TiO2 particles in water by RF-plasma polymerization of poly(acrylic acid) on the particle surface

The stability of TiO2 particles in water was increased through plasma polymerization of acrylic acid (AA) onto the particles surface. The polymerization was carried out directly upon TiO2 powder by using two radiofrequency (RF) plasma reactors: one inductively coupled and another capacitively coupled. In both cases, a cross-linked polyacrylic acid (PAA) film was formed on TiO2 particles surface, which was characterized by Energy Dispersive Spectroscopy (EDS), Fourier-transformed infrared spectroscopy, (FTIR), Raman Spectroscopy, and X-ray photoelectron spectroscopy (XPS). The stability of the PAA-coated TiO2 particles was determined by their precipitation in water. It was found that a moderate plasma treatment effectively improved the stability of PAA-coated TiO2 particles. At low levels of AA polymerization, the TiO2 particles surface was not modified enough to improve their stability in water; on the other hand, a high degree of AA polymerization led to the formation of large agglomerates, induced by the PAA film, and these particles were not stable. As expected, the particle size and the Z-potential of the PAA-coated particles determined their stability in water. Under the optimum operating conditions of this study, the treated TiO2 particles showed stability as good as that of TiO2 particles modified with a dispersant.

Effect of pH, polymer concentration and molecular weight on the physical state properties of tolfenamic acid

Tolfenamic acid (TA) has been transformed from crystalline to amorphous state through freeze-drying by using varying ratios of polyacrylic acid (PA) at various pH values. The characterization of the films has been carried out using X-ray diffraction, differential scanning calorimetry, Fourier transform infrared (FTIR) spectrometry and scanning electron microscopy. The results showed a gradual change in the solid state properties of TA and a complete transformation into its amorphous form in 1:8, 1:4, 1:2 and 1:1 ratios at pH 3, 4, 5 and 6, respectively. FTIR spectrometry reveals the formation of a yellow polymorphic form of TA. Polymer molecular weight has also been observed to affect the drug transformation and interaction as the low molecular weight PA (Mw ∼ 1800) was found to be most effective followed by its medium (Mv ∼ 450 000) and high molecular weight (Mv ∼ 3 000 000) forms. No signs of recrystallization in the TA–PA films were noted during the 12-week storage period. PA of low molecular weight has also been found more effective in inhibiting the recrystallization of the melt upon cooling thus proving a valuable polymer in producing stable amorphous solid dispersions of TA.

Polymer Spraying for Aerosol Jet Etching of Dielectrics for 156-mm Silicon Wafers

ABSTRACTThe front surface of dielectric passivated silicon wafers were spray coated with polyacrylic acid (PAA) using an ultrasonic coating system. A simple model was proposed to correlate the degree of coverage with the number of spray passes. The sprayed PAA films enabled good etching of the dielectric, using a process referred to as aerosol jet etching (AJE), despite the fact that the PAA thickness was non-uniform over the substrate. The AJE tip-to-substrate distance and diameter of the tip were tuned to balance process throughput and the etched line width. Controlling the level of condensation in the aerosol jet printer (AJP) fluid path was critical for etching 156-mm pseudo square silicon wafers.

Post-synthesis treatment for improving zeolite coating stability

Zeolite A and zeolite X coatings prepared by using the substrate heating method were coated by polyacrylic acid films in order to improve their stabilities. Various synthesis conditions were used to obtain coatings of different thicknesses. X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-Transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) were used to characterize the materials prepared. The mechanical and thermal stabilities of the coatings were determined by the application of consecutive ultrasonic treatments and heating/cooling cycles, respectively. It was observed that the post-synthesis treatment applied to zeolite coatings improved the stabilities of these materials. The thin polyacrylic acid films were well integrated with the zeolite crystals and did not lead to any problem regarding water desorption from the samples investigated.

Electrophoretic deposition of polyacrylic acid and composite films containing nanotubes and oxide particles

Electrophoretic deposition (EPD) method has been developed for the deposition of thin films of polyacrylic acid (PAA). This method allowed the formation of uniform films of controlled thickness on conductive substrates. It was shown that PAA can be used as a common dispersing agent suitable for charging and EPD of various materials, such as multiwalled carbon nanotubes, halloysite nanotubes, MnO2, NiO, TiO2 and SiO2. The feasibility of EPD of composite films containing the nanotubes and oxide particles in a PAA matrix has been demonstrated. The kinetics of deposition and deposition mechanisms were investigated and discussed. The films were studied by thermogravimetric analysis, differential thermal analysis, X-ray diffraction and scanning electron microscopy. The results indicated that film thickness and composition can be varied. Obtained results pave the way for the fabrication of PAA and composite films for biomedical, electrochemical and other applications.

Supercapacitor behavior of CuO–PAA hybrid films: Effect of PAA concentration

The Cu–poly(acrylic) acid (PAA) thin films were deposited at room temperature by a simple and cost effective polymer assisted deposition (PAD) method. The solution containing Cu salt and PAA was spin coated to yield the thin films with desired properties. The Cu–PAA films were annealed at 400 °C in ambient air for 4 h to obtain CuO–PAA phase. The effect of PAA concentration on the film properties is studied and characterized by employing various techniques. The structural and surface morphological studies are carried out using X-ray diffraction (XRD) and scanning electron microscope (SEM) respectively. Fourier transform infrared spectroscopy (FT-IR) and FT-Raman spectroscopy are employed to investigate the hybrid film formation. Wetting behavior is studied by measuring the contact angle of water on the film surface. Cyclic voltammetry (CV) studies were carried out to investigate the specific capacitance of CuO–PAA films in aqueous 1 M H 2SO 4 electrolyte. Hybrid films deposited with 2 mM PAA exhibits highest specific capacitance of 65 F g −1.

Stability study of polyacrylic acid films plasma-polymerized on polypropylene substrates at medium pressure

Plasma polymerization of acrylic acid has become an interesting research subject, since these coatings are expected to be beneficial for biomedical applications due to their high surface density of carboxylic acid functional groups. However, the application of these monomers is counteracted by their low stability in humid environments, since a high stability is a required characteristic for almost any biological application. The present work investigates whether it is possible to obtain stable deposits with a high retention of carboxylic acid functions by performing plasma polymerization on polypropylene substrates with a dielectric barrier discharge operating at medium pressure. In order to obtain coatings with the desired properties, the plasma parameters need to be optimized. Therefore, in this paper, the influence of discharge power and location of the substrate in the discharge chamber is examined in detail. The properties of the deposited films are studied using contact angle measurements, X-ray photoelectron spectroscopy, atomic force microscopy and Fourier transform infrared spectroscopy. Moreover, to determine whether the obtained deposits are soluble in water, the coatings are once again analyzed after rinsing in water. This paper will clearly show that stable COOH-rich surfaces can be obtained at high discharge power and close to the monomer inlet, which might open perspectives for future biomedical applications.

Electrochemical-switchable polymer film: An emerging technique for treatment of metallic ion aqueous waste

The present work aims at using grafted polyacrylic acid (PAA) films as active surfaces for heavy metal waste removal. We focus first on grafting PAA onto carbon felt surfaces by means of an economical and simple preparation method compatible with real industrial applications. XPS, SEM results and interfacial electrochemistry allow us to confirm the grafting of PAA films on carbon felts. Metal ion uptake inside the PAA film is discussed in detail. The final part of the work is then devoted to the application of carbon felt grafted PAA electrodes to remove metal ions from aqueous waste according to the electrochemical-switchable process. Primary treatments of real industrial effluents are performed with a lab-made semi-pilot system. Such electrochemical-pH-switchable PAA films can be considered within the field of aqueous effluent treatments in order to reach very low concentration in heavy metal ions.

Electrochemical behaviour of polyacrylic acid coated gold electrodes: An application to remove heavy metal ions from wastewater

An efficient and low cost preparation method (Diazonium-Induced Anchoring Process) to graft polyacrylic acid (PAA) on the gold substrate has been reported. IR, XPS and AFM techniques were used to characterize the obtained polymer film. The interfacial electrochemistry of the PAA coated gold electrodes was studied by means of impedance spectroscopy and cyclic voltammetry transition techniques. The ability of PAA-grafted onto a gold electrode to reversibly bind or release metal ions was confirmed. As a broad-range chelating material, PAA is able to capture several heavy metal ions at low concentration. The release of those metal ions from the grafted PAA film was obtained under electro-induced-acidification by applying an anodic potential at the electrode to promote a localized water electrolysis. Application of electrochemical-pH-switchable PAA films can be considered within the field of heavy metal waste treatments.

Electro-switchable surfaces for heavy metal waste treatment: Study of polyacrylic acid films grafted on gold surfaces

This paper focuses on using electrochemical-pH-switchable polymer films as active surfaces for heavy metal waste treatment. Polyacrylic acid (PAA) was grafted at open air and room temperature on gold substrates. As a broad-range chelating material, PAA can capture heavy metal ions at low concentration. The release of the metal ions from the grafted-PAA film was obtained under electro-induced-acidification by applying an anodic potential at the electrode to promote a localized water electrolysis. Such electrochemical-switchable films can be part of a secondary step-treatment after conventional ion exchange process or precipitation for treatment of aqueous effluents in order to reach very low concentration in heavy metal ions without production of secondary effluents.

Study of Protein Adsorption onto a Polymer Film by in-situ UV Attenuated Total Reflectance Spectroscopy

AbstractOur work presents results on human plasma protein adsorption onto a polyacrylic acid (PAA) film prepared via surface wave plasma (SWP) induced graft polymerization. The PAA film prepared in this manner is characterized by a carboxyl functional group and a constant contact angle in water of 35°. The adsorption kinetics of human plasma fibrinogen (HPF) and human serum albumin (HSA) proteins were measured by in-situ UV-ATR spectroscopy. The free energy of adsorption on PAA treated as well as untreated surfaces was −28 kJ M−1 and −22 kJ M−1 for HPF and HSA, respectively, regardless of surface chemistry. We determined that 14 μM and 6 μM HPF concentrations are enough to cover half of the maximum possible of surface coverage on silica and PAA film, respectively. HSA protein concentrations of 154 μM and 118 μM are enough to cover half of the maximum accessible surface of silica and PAA film, respectively. For surface treatment of implants with PAA polymer and protein, the necessary protein concentration for effective surface coverage should be known.

Water and ammonia influence on the conduction mechanisms in polyacrylic acid films

Abstract Polyacrylic acid (PAA) and ammonium polyacrylate (NH4PA) films realised on quartz substrate with platinum interdigitated electrodes have been investigated under controlled atmosphere by the means of impedance spectroscopy and square-wave potentiostatic experiments. Using the standard analysis of Cole–Cole plots, the dependence on ambient conditions of the equivalent circuit parameters has been derived. The samples’ behaviour indicates two different conduction mechanisms, which depend on the humidity and ammonia content of the ambient. Additionally, infrared transmission spectroscopy measurements were performed on PAA films deposited onto Germanium optical windows in order to study the irreversible reaction of PAA with ammonia in humid air.

Deposition of Organic Coatings at Atmospheric Pressure from Liquid Precursors

AbstractThis paper reports on the deposition of organic coatings on flat substrates using atmospheric pressure plasma systems. Special attention will be paid on the use of liquid monomer as the precursor, injected directly into the plasma region, or in post‐discharge. We will also present an original technology that combines a dielectric barrier discharge and an electrohydro dynamic atomisation (EHDA) system to deposit well‐defined polyacrylic acid films. The advantage of such system is the possibility to limit the extent of the monomer fragmentation and to give rise to rapid deposition of a highly functionalised plasma polymer layer.magnified image

Analytical investigations of poly(acrylic acid) coatings electrodeposited on titanium-based implants: a versatile approach to biocompatibility enhancement

A polyacrylic acid film was synthesized on titanium substrates from aqueous solutions via an electroreductive process for the first time. This work was done in order to develop a versatile coating for titanium-based orthopaedic implants that acts as both an effective bioactive surface and an effective anti-corrosion barrier. The chemical structure of the PAA coating was investigated by X-ray photoelectron spectroscopy (XPS). Scanning electron microscopy (SEM) was employed to evaluate the effect of annealing treatment on the morphology of the coatings in terms of their uniformity and porosity. Inductively coupled plasma mass spectrometry was used to measure ion concentrations in ion release tests performed on Ti-6Al-4V sheets modified with PAA coatings (annealed and unannealed). Results indicate that the annealing process produces coatings that possess considerable anti-corrosion performance. Moreover, the availability and the reactivity of the surface carboxylic groups were exploited in order to graft biological molecules onto the PAA-modified titanium implants. The feasibility of the grafting reaction was tested using a single aminoacid residue. A fluorinated aminoacid was selected, and the grafting reaction was monitored both by XPS, using fluorine as a marker element, and via quartz crystal microbalance (QCM) measurements. The success of the grafting reaction opens the door to the synthesis of a wide variety of PAA-based coatings that are functionalized with selected bioactive molecules and promote positive reactions with the biological system interfacing the implant while considerably reducing ion release into surrounding tissues.

Ammonia detection mechanism with polyacrylic acid sensitive layers: Field effect transduction

The origin of work-function (WF) changes induced in polyacrylic acid (PAA) layers deposited on metallic electrodes upon ammonia exposure is examined. The changes are recorded in experiments performed in Kelvin Probe (KP) set-ups. To understand and explain the origin of the signals, data gathered in gravimetric (QMB), morphology, direct current (dc) conductance, 4 MHz conductance and 4 MHz capacitance investigations are also used. The origin of the measured KP effects seems to be the polymer–electrode interface enriched in target gas molecules by the absorption in the PAA film. In this context, the complex role of the polymer and background humidity is addressed.

High sensitivity polyacrylic acid films for ammonia detection with field effect devices

Thin polyacrylic acid (PAA) films, with defined geometry, have been produced by spray deposition from dilute polymer solutions on metal plated wafers. The layer morphology was characterized by standard methods: optical, atomic force and scanning electron microscopy; stylus and optical profiler. Their sensing properties toward ammonia as target gas and the related cross sensitivities towards the most relevant interferents have been determined by the Kelvin Probe (KP) technique. The influence of the deposition parameters, layer thickness, operating temperature and aging were also investigated. The study was made in order to investigate the potential of PAA as sensing material for room temperature field effect gas sensors.

Redox-Switching of Electrorefractive, Electrochromic, and Conductivity Functions of Cu2+/Polyacrylic Acid Films Associated with Electrodes

A polyacrylic acid film saturated with Cu2+ ions displays redox-switchable electrorefractive, electrochromic, and conductivity functions upon reduction of Cu2+ to Cu0. Surface plasmon resonance spectroscopy, adsorption spectroscopy, and conductivity measurements are used to examine these functions, which are demonstrated to be fully reversible. New types of optical filters and modulators, optoelectronic devices, and smart windows could potentially be constructed from such hybrid polymers.

Spectroscopic properties of Na-fluorescein in polyacrylic acid films

Na-fluorescein (NaF), when embedded in thin polyacrylic acid (PAA) films, shows a single absorption band peaking at 444 nm and an emission band peaking at 505 nm. The quantum yield of fluorescence ( Q f) of the NaF/PAA film is 0.65. These spectroscopic properties of NaF in PAA films can be attributed to the existence of a neutral zwitterionic form of NaF with a small percentage of a cationic form of NaF within the PAA film.

Lasing action of rhodamine B in polyacrylic acid films

Rhodamine B (Rh-B) has been embedded in PolyAcrylic acid (PAA) films. The materials are studied for the laser action with nitrogen laser excitation. The lasing efficiency of Rh-B/PAA films is comparable to that of rhodamine 6G in methanol. There is a 50% reduction in the laser intensity of the films with 2600 pulses from the N2 laser (2 Hz). The photostability of these materials is far superior to that of other polymeric materials and is comparable to that of sol–gel materials.

XPS studies of metal/polymer interfaces — Thin films of Al on polyacrylic acid and polyethylene

A reactivity experimental study of Al with CH 2 and COOH functionalities in polymers is performed using polyacrylic acid (PAA) and low density polyethylene (LDPE). The Al metal is deposited on the polymer surfaces using in-situ sputter deposition. Using X-ray photoelectron spectroscopy (XPS), an Al oxide-carbide complex is identified at the PAA/Al interface while an Al carbide-like species is observed at the LDPE/Al interface. These conclusions are based on carefully referenced binding energy measurements of the C(1s), O(1s), and Al(2p) core electron levels. Near surface XPS studies involving solvent cast PAA films indicate that they are CH 2 rich, suggesting that a larger than statistical number of carboxylic acid groups are pointing away from the surface towards the bulk. PAA powder, however, is found to have near stoichiometric composition at the surface. The conclusions regarding Al/polymer reactivity agree well with recent literature for other metal/polymer interfaces.