Acrylic Acid Vapor Research Articles

Enhanced glycerol dehydration of pervaporation cross‐linkedPVAmembranes modified byVUV/UV‐Ctreatments

AbstractThe high glycerol miscibility in water needs more efficient processes to decrease the cost of dehydration. Water stable poly(vinyl alcohol) based membranes cross‐linked with 15% w/w of maleic acid were used for dehydrating glycerol‐water mixtures using pervaporation (PV). The membranes were characterized using water contact angle, profilometry, Fourier transformed infrared spectroscopy‐attenuated total reflectance, x‐ray photoelectron spectroscopy, water stability, swelling tests, and PV. Membranes were treated using dry methods with vacuum ultraviolet (VUV; 162 nm) or ultraviolet (UV)‐C (254 nm) radiation and exposed to O2or acrylic acid vapors, respectively. The VUV and UV‐C treatments improve PV performances, increasing the water separation selectivity more than 4 and 8.5 times, respectively. UV‐C treatments exhibit a water flux (kg m−2h−1), selectivity and PSI (kg m−2h−1) of 0.3, 250, and 87.4 respectively. Highly hydrophilic functional groups grafted onto the surface of the membranes after irradiation favor the selective transfer of water through the membrane. Overall, the VUV or UV‐C membrane treatments show great PV prospect in glycerol dehydration.

Pulsed plasma surface functionalized nanosilver for gene delivery.

Lack of suitable surface properties in biomaterials is an acute challenge for their utilization in nucleic acid delivery, since surface plays a vital role in cell adhesion/uptake and immunity. Low pressure cold plasma is a promising technology for functionalization and surface modification of materials, in an effective, environment friendly and economical way. In this investigation we have modified the surface of silver nanoparticles (AgNPs) with chitosan biopolymer, using plasma treatment, to extend their application scope in intracellular DNA delivery. The plasma functionalized; chitosan modified AgNPs (MetaloPolymeric Nanocarriers; MPNCs) possessed superior biocompatibility compared to unmodified AgNPs. Carboxylic groups were incorporated on the surface of nanosilver using 3600 rotating pulsed plasma reactor and acrylic acid vapors were used as precursor gas. Pulsed plasma polymerization process was optimized with respect to working pressure of the system, duty cycle for pulsing, time of treatment and flow rate. Biocompatibility of the plasma functionalized nanosilver was enhanced by coupling it with Chitosan Oligosaccharide (COS), using EDC (1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide) to form amide linkages. The resulting MPNCs showed high cell viability and bio-stability, which was attributed to plasma processing of nanosilver and its association with COS. In vitro cellular studies illustrated significant uptake of nanoplexes. The study suggested the potential of plasma functionalization for manipulating surfaces of metallic nanoparticles to enhance their application in intracellular gene delivery.

Plasma Treatment of Polymer Powder as an Effective Tool to Functionalize Polymers: Case Study Application on an Amphiphilic Polyurethane.

Plasma treatment is a widely applied, easy, fast, and highly reproducible surface modification technique. In this work powder plasma treatment was exploited to expose carboxylic groups along the backbone of a water soluble polymer. Specifically, a custom-made amphiphilic poly(ether urethane) containing Poloxamer® 407 blocks (Mw = 54,000 Da) was first synthesized and its powders were plasma treated in the presence of Acrylic Acid vapor. To maximize –COOH group exposure while preventing polymer degradation, different Ar gas flow rates (i.e., 10, 30, and 50 sccm) were investigated. Upon gas flow increase, significant polymer degradation was observed, with a 35% molecular weight reduction at 50 sccm Ar flow rate. On the other hand, the highest number of exposed carboxylic groups (5.3 × 1018 ± 5.5 × 1017 units/gpolymer) was obtained by setting gas flow at 10 sccm. Hence, a gas flow of 10 sccm turned out to be the best set-up to maximize –COOH exposure while preventing degradation phenomena. Additionally, upon plasma treatment, no detrimental effects were observed in the thermoresponsiveness of polymer aqueous solutions, which was ensured by Poloxamer® 407 blocks. Therefore, the newly developed technology here applied on an amphiphilic poly(ether urethane) could pave the way to the tailored design of a plethora of different multifunctional hydrogels.

Deposition of a stable and high concentration of carboxylic acid functional groups onto a silicon surface via a tailored remote atmospheric pressure plasma process

Processes to introduce carboxylic acid functional groups onto surfaces have been widely applied in various applications, such as molecular grafting for biosensors, biocompatibility improvement, gas filter/adsorption in environmental engineering and the enhancement of interfacial adhesion between fillers (such as carbon or glass fibre) and matrices (such as epoxy resin) in composite materials. To develop an environmental-friendly process to introduce a stable and high concentration of carboxylic acid functional groups, Acrylic Acid (AAc) was deposited onto silicon wafers using remote argon atmospheric plasma processing (APP) and vapour phase grafting in a bespoke Pyrex cylindrical chamber. The chamber stands vertically with an APP nozzle installed at the top, a sample platform downstream and an AAc vapour inlet on the chamber wall. In this way, both the effect of atmospheric gas on the process and AAc monomer fragmentation during APP can be limited. Silicon specimens were exposed to a combination of plasma gas and AAc vapour. Surface wettability was evaluated by measurement of water contact angles and chemical composition was analyzed using X-ray Photoelectron Spectroscopy (XPS). The peak at the binding energy of 289.2eV, which fits with COOH components in the C1s spectrum of poly-AAc, was used to determine the contribution of the carboxylic acid groups depositing on the surface because it was absent in the C1s peak of untreated silicon wafers. A more stable and hydrophilic wettability and the binding energy peak at 289.2eV from XPS show the presence of carboxylic acid groups on the surface of samples treated with AAc vapour with the remote argon-APP. A higher intensity peak at 289.2eV was detected, compared with the surfaces activated by a conventional argon-APP in which the AAc vapour is exposed to the plasma glow, suggesting a potential, rapid and novel remote APP process for carboxylic acid functional group deposition.

UV-Surface Treatment of Fungal Resistant Polyether Polyurethane Film-Induced Growth of Entomopathogenic Fungi.

Synthetic polymers are the cause of some major environmental impacts due to their low degradation rates. Polyurethanes (PU) are widely used synthetic polymers, and their growing use in industry has produced an increase in plastic waste. A commercial polyether-based thermoplastic PU with hydrolytic stability and fungus resistance was only attacked by an entomopathogenic fungus, Metarhiziumanisopliae, when the films were pre-treated with Ultraviolet (UV) irradiation in the presence of reactive atmospheres. Water contact angle, Fourier transform infrared spectroscopy in attenuated total reflection mode (FTIR-ATR), scanning electron microscopy (SEM), and profilometer measurements were mainly used for analysis. Permanent hydrophilic PU films were produced by the UV-assisted treatments. Pristine polyether PU films incubated for 10, 30, and 60 days did not show any indication of fungal growth. On the contrary, when using oxygen in the UV pre-treatment a layer of fungi spores covered the sample, indicating a great adherence of the microorganisms to the polymer. However, if acrylic acid vapors were used during the UV pre-treatment, a visible attack by the entomopathogenic fungi was observed. SEM and FTIR-ATR data showed clear evidence of fungal development: growth and ramifications of hyphae on the polymer surface with the increase in UV pre-treatment time and fungus incubation time. The results indicated that the simple UV surface activation process has proven to be a promising alternative for polyether PU waste management.

Molecular-Level Reinforced Adhesion Between Rubber and PTFE Film Treated by Atmospheric Plasma Polymerization

Extremely strong reinforced adhesion between a polytetrafluoroethylene (PTFE) film and butyl rubber is achieved using an atmospheric pressure plasma graft polymerization, involving argon and acrylic acid vapor. The treated PTFE film is then placed over a raw butyl rubber plate and hot-pressed under 157 N/cm2 for 40 min at 150 °C or for 10 min at 180 °C. This procedure results in molecular-level or chemical adhesion between the butyl rubber and the PTFE film. The 180° peeling test results show that a high peeling strength of 3.9 N, per 1 mm sample width, is achieved. Adherend failure of the rubber sheet occurs when the peeling is enforced. From X-ray photoelectron spectroscopy analysis of the treated films, chemical bonds with fluorine atoms are absent from the surface. From scanning electron microscopy analysis, a transparent hydrophilic poly(acrylic acid) layer composed of nanoscale spherical particles is formed. This PTFE-rubber composite material is suitable for high-quality, prefilled medical syringe gaskets.

Bovine lactoferrin and lactoferricin on plasma-deposited coating against spoilage Pseudomonas spp.

Abstract Bovine lactoferrin and lactoferricin B, well-known for their antimicrobial properties, were individually immobilized on two different coatings functionalized with − COOH groups deposited in the inner part of polyethylene micro tubes by means of a plasma deposition (PE-CVD) process fed with ethylene and acrylic acid vapors. The resulting functionalized tubes were tested for antimicrobial activity against three Pseudomonas strains responsible for casein hydrolysis and cheese pigmentation. The cell counts of these spoilage bacteria, incubated for 30 h under their optimal growth conditions, were found to be significantly reduced after 24 h in micro tubes functionalized with lactoferricin B, whereas a very low antimicrobial activity against the same strains, often undistinguishable from that of control samples, was observed in tubes functionalized with lactoferrin. This is the first work in which a plasma coating functionalized by lactoferricin B was studied to make an active packaging useful to control cheese spoilage by Pseudomonas . Industrial relevance The current study describes a new method to immobilize two food grade proteinaceous natural compounds. The resulting plasma-functionalized lactoferricin B-immobilized coating is a promising tool for the control of spoilage microorganisms and shelf-life extension of cheeses.

Which is more effective for protein adsorption: surface roughness, surface wettability or swelling? Case study of polyurethane films prepared from castor oil and poly(ethylene glycol)

AbstractIn order to investigate the effects of surface roughness, surface wettability and swelling on protein adsorption, polyurethane films were prepared from castor oil (CO) and poly(ethylene glycol)‐3000 (PEG) using one‐shot bulk polymerization. Hexamethylene diisocyanate and 1,4‐butanediol were used as isocyanate and chain extender, respectively. The hydrophilicity of the polyurethane films was adjusted by varying the ratio of CO to PEG. The surface of the polyurethane films was treated using plasma polymerization in the presence of acrylic acid vapour. Therefore, the polyurethane films could be obtained with the same hydrophilicity but with different roughness. The hydrophilicity of untreated and treated polymer films was examined using contact angle measurements. The surface topology of the polymer films was investigated using scanning electron microscopy and atomic force microscopy. Adsorption of bovine serum albumin and bovine serum fibrinogen on treated and untreated polymer films was determined and the performance of the films was compared. After evaluation of all results it is found that surface roughness and swelling are as important as hydrophilicity for protein adsorption in the case of CO/PEG‐based polyurethanes. © 2012 Society of Chemical Industry

Evidence of Carboxyl Modification of Hydrogen-Free Diamond-Like Carbon Films Assisted by Radio Frequency Plasma in Vacuum

Modification of hydrogen-free diamond-like carbon (DLC) is presented, with acrylic acid (AA) vapor carried into a vacuum chamber by argon and with the in situ assistance of low-power radio frequency (RF) plasma at a temperature below 100°C. Measured by atomic force microscopy (AFM) technique, the roughness (Ra) of the DLC was 1.063±0.040 nm. XPS and FT-IR spectra analysis showed that carboxyl groups were immobilized on the surface of the DLC films, with about 40% of carboxyl group area coverage. It was found that the RF plasma and reaction time are important in enhancing the modification rate and efficiency.

PE‐CVD of Hydrophilic‐COOH Functionalized Coatings on Electrolyte Gated Field‐Effect Transistor Electronic Layers

AbstractA plasma deposition (PE‐CVD) process is proposed to functionalize the surface of P3HT organic semiconductor with an hydrophilic coating characterized by carboxyl groups. The functionalized P3HT is employed as electronic active layer in an electrolyte gated organic field‐effect transistor (EGOFET). Nanometric coatings were plasma deposited at the surface of P3HT from glow discharges fed with ethylene and acrylic acid vapors. The surface chemical composition of coated P3HT along with its wettability, have been assessed by means of X‐ray photoelectron spectroscopy and water contact angle. Results show that PE‐CVD is a valid approach to functionalize P3HT surfaces with carboxyl groups, leaving negligible adverse effect on the EGOFET performances. Possibly, chemical or biological species could be immobilized on PE‐CVD‐functionalized EGOFETs, opening to further developments in their use as sensors. magnified image

Controlling the surface wettability of poly(sulfone) films by UV‐assisted treatment: benefits in relation to plasma treatment

AbstractHydrophilic and superhydrophilic surfaces of poly(sulfone) (PSU) thin films were prepared by UV irradiation in the presence of O2 or acrylic acid (AA) vapor. Treated surfaces were then investigated by water contact angle measurements, Fourier transformed IR spectroscopy in attenuated total reflectance mode (FTIR‐ATR), X‐ray photoelectron spectroscopy (XPS), near‐edge X‐ray absorption fine structure (NEXAFS) and AFM. Water contact angle values of treated PSU films using either O2 or AA vapor as the reactive atmosphere reached about 6° after more than 120 min of irradiation. FTIR‐ATR, XPS and NEXAFS analysis showed incorporation of oxygenated groups onto the surface that led to its hydrophilic characteristics. In addition, when AA vapor was used as the reactive atmosphere, a photopolymerization process of poly(acrylic acid) onto the surface of the PSU was observed. AFM analysis showed a very low level of roughness after the treatments. A comparison of UV‐assisted surface modifications of PSU films with traditional plasma treatments showed excellent qualitative agreement between the two techniques. Our results show that UV‐assisted treatments in the presence of AA vapor or O2 are efficient ways of controlling the surface wettability and functionalities grafted on the surface of PSU films. This treatment can be considered as a permanent dry grafting method that resists aging and uses a simple experimental setup. © 2012 Society of Chemical Industry

Polymerized nanoporous titania surfaces: modification of cell adhesion by acrylic acid functionalization

Nanoporous titania (nPTI) has been prepared by electrochemical processes and functionalized by photochemical activation of condensed acrylic acid vapors (AcAc). The nPTI surfaces obtained after electrochemical etching in HF electrolytes at constant potential consisted of nanotube disordered arrays. Elastic recoil detection and Rutherford backscattering spectroscopy studies confirm the presence of an in-depth carbon based layer, previous to the AcAc polymerization. The subsequent AcAc functionalization affected only a few molecular monolayers since the process did not modify the nPTI structure observed by scanning electron microscopy. In fact, X-ray photoelectron spectroscopy confirms the presence of a carboxylic group contribution in the C 1s core-level spectrum only after AcAc polymerization of nPTI. Such results are of relevance for cellular attachment of human mesenchymal stem cells, whose adhesion onto nPTI is drastically enhanced after AcAc biofunctionalization.

Haemocompatibility improvement of metallic surfaces by covalent immobilization of heparin–liposomes

Stainless steel surfaces were processed by means of plasma enhanced chemical vapor deposition (PE-CVD) fed with acrylic acid vapors in order to functionalize them with carboxyl groups, which were subsequently activated for covalent immobilization of heparin-loaded (HEP) NH2 group-functionalized (Fun) nanoliposomes (NLs). Empty Fun or HEP non-functionalized (control) NLs were used as controls. NLs were characterized for mean diameter, surface charge and heparin encapsulation/release. Different lipid compositions were used for NL construction; PC/Chol (2:1mol/mol) or PC/Chol (4:1mol/mol) (fluid type vesicles) [which allow gradual release of heparin] and DSPC/Chol (2:1mol/mol) (rigid type vesicles). Surface haemocompatibility was tested by measuring blood clotting time. Platelet adhesion on surfaces was evaluated morphologically by SEM and CLSM. The haemocompatibility of plasma-processed surfaces was improved (compared to untreated surfaces); Fun-HEP NL-coated surfaces demonstrated highest coagulation times. For short surface/blood incubation periods, surfaces coated with Fun-HEP NLs consisting of PC/Chol (2:1) had higher coagulation times (compared to DSPC/Chol NLs) due to faster release of heparin. Heparin release rate from the various NL types and surface platelet adhesion results were in agreement with the corresponding blood coagulation times. Concluding, covalent immobilization of drug entrapping NLs on plasma processed surfaces is a potential method for preparation of controlled-rate drug-eluting metallic stents or devices.

Direct immobilization of avidin protein on AFM tip functionalized by acrylic acid vapor at RF plasma

The atomic force microscopy (AFM) has been used as a force sensor to measure unbinding forces of single bound complexes in the nanonewton and piconewton range. Force spectroscopy measurements can be applied to study both intermolecular and intramolecular interactions of complex biological and synthetic macromolecules. Although the AFM has been extensively used as a nano force sensor, the commercially available cantilever is limited to silicon and silicon nitride. Those materials reduce the adhesion sensitivity with specific surface and/or molecule. Here, we functionalized the AFM tip with carboxylic groups by applying acrylic acid (AA) vapor at radio frequency plasma treatment at 100 W for 5 min. This method provides a remarkable sensitivity enhancement on the functional group interaction specificity. The functionalized tip was characterized by scanning electron microscopy. The electron beam high resolution images have not shown significant tip sharpness modification. Silicon wafers (1 0 0)-no treated and functionalized by AA plasma treatment-were characterized by Auger electron spectroscopy to elucidate the silicon surface sputtering and demonstrate functionalization. The Fourier transform-infrared spectroscopy spectrum shows a high absorbance of avidin protein over the silicon surface functionalized by AA plasma treatment.We carried out force spectroscopy assay to measure the unbinding force between the well-established pair biotin-avidin. At pulling speed of 2 µm/s, we measured the unbinding force of 106 ± 23 pN, which is in good agreement with the literature, demonstrating the effectiveness of the tip functionalization by AA plasma treatment in biological studies.

Surface Modification of Synthetic Polymers Using UV Photochemistry in the Presence of Reactive Vapours

AbstractPolystyrene (PS), Polyurethane (PU), Polysulfone (PSU) and Polypropylene (PP) were surface modified using UV assisted treatment in the presence of acrylic acid (AA) vapour. In this context, PU and PSU were also modified using vapour of trimethoxy propyl silane (TMPSi). The surface changes were characterized by water contact angle measurement, Fourier transform infrared spectroscopy – Attenuated total reflection and X‐ray photoelectron spectroscopy. Permanent hydrophilic surface was obtained by UV assisted treatment in the presence of AA vapour on all polymers studied. After 65 days of treatment, the polymer surfaces had the original degree of hydrophilicity as obtained immediately after treatment. By using vapour of TMPSi with UV radiation, the surface hydrophobicity of PU and PSU was increased after thermal treatment. The surface modification methodology used was simple and did not require any extensive set‐up compared to traditional surface modification techniques.

Improvement of the adsorption properties of carbon black granules by means of plasma enhanced-chemical vapour deposition with acrylic acid vapours

Carbon black granules were coated by thin polymers in radio frequency glow discharges fed with acrylic acid/argon mixtures at different input powers, in order to improve the adsorption ability of basic compounds in the liquid and gas phases. The treated surfaces were characterized by X-ray photoelectron spectroscopy analyses and water contact angle measurements, performed immediately after the plasma treatment, after ageing in water and in air, and after heating up to 150 °C. The adsorption ability of basic compounds in the liquid and gas phases was evaluated with Boehm titrations and ammonia adsorption, respectively. Scanning electron microscopy observations and Brunauer, Emmett, Teller specific surface area measurements were performed to evaluate the morphological changes induced by the plasma treatments on the carbon black granule surface. The results show that the plasma treatments significantly improve the absorption ability of carbon black mainly for grafting of carboxylic groups and not for surface morphological modifications.

Preparation of PTFE Film With Adhesive Surface Treated by Atmospheric-Pressure Nonthermal Plasma Graft Polymerization

A surface modification technique that improves the adhesion of fluorocarbon polymer films such as polytetrafluoroethylene (PTFE), perfluoroalkoxy fluoroplastics, and polychlorotrifluoroethylene is developed using argon at atmospheric pressure and acrylic acid vapor nonthermal plasma. The results of the T-type peeling test show that the peeling strength of the treated PTFE film is approximately 70 times greater than that of the untreated film. From X-ray photoelectron spectroscopy and scanning electron microscope analyses, it is confirmed that chemical bonds with F atoms decrease greatly on the surface and that a hydrophilic layer is formed due to the plasma graft polymerization process. Using the present surface treatment apparatus, it is possible to bond A4-sized sheets of PTFE and metals without losing the excellent physical properties of PTFE.

Polymer Surface Functionalization Using Plasma, Ultraviolet and Synchrotron Radiation

Polyurethane (PU) and polystyrene (PS) films were functionalized by ultraviolet (UV) or selective synchrotron radiations (SR) in the presence of reactive gases. The UV-PU results were compared with lowpressure plasma treatments of the same films. Oxygen or acrylic acid vapours (AA) were used as reactive gases. X-ray photoelectron spectroscopy measurements of UV modified films in the presence of oxygen or AA matched the RF-plasma treatments results. It is shown that COO and C=O functional groups were incorporated at the polymer surface efficiently with both methodologies. In addition, near-edge X-ray absorption fine structure showed that a thin film of poly(acrylic acid) is formed over the PU and PS films during the UV irradiation in the presence of AA vapours. These results resemble previous AA low-power plasma treatments. PU and PS films were also selectively functionalized by SR using oxygen as reactive gas. Surface concentrations of COO and C=O functional groups were enhanced by C1s → σ* C–C excitation after irradiation and oxygen introduction. This efficient surface functionalization was clearly observed in PS films which do not have CO and COO groups in their molecular structure. Excitations involving transitions to π* orbital (π*C=C, π*C=O) led to much lower functionalization efficiency. The SR results can be explained by taking into account previous photon stimulated ion desorption studies of polymers. SR results may open new ways to functionalize polymer surfaces selectively and efficiently.

Ultraviolet-induced surface modification of polyurethane films in the presence of oxygen or acrylic acid vapours

An efficient surface functionalization of polyurethane (PU) films has been obtained by ultraviolet (UV)-assisted modification in the presence of oxygen or acrylic acid (AA) vapours. Film analyses were carried out by water contact angle measurements, X-ray photoelectron spectroscopy (XPS) and Near-edge X-ray absorption fine structure (NEXAFS). Film hydrophilicity increased with photolysis time in the presence of oxygen or AA vapours. Incorporation of COO and C O functional groups at the polymer surface after the UV-assisted treatments was observed. In addition, High resolution XPS and NEXAFS results showed that a thin film of poly (acrylic acid) (PAA) is formed over the PU films during the UV irradiation with AA vapours. The obtained results are compared with previous published oxygen and AA low-power plasma treatments. Similarity between both treatment methodologies is shown. UV surface functionalization and polymerization of PAA can be used instead of a traditional plasma treatment with the advantage of set-up simplicity and lower costs.

Plating Technology for Fluorocarbon Polymer Films Using Atmospheric-pressure Nonthermal Plasma Graft Polymerization

A low-environmental load surface modification technique for plating the fluorocarbon polymers films is developed using an atmospheric-pressure argon and acrylic acid vapor nonthermal plasma graft polymerization. The results of the T-type peeling test show that the peeling strength of copper plating on the treated PTFE (polytetrafluoroethylene) film is approximately 46 times greater than that on the untreated film. With scanning electron microscope analysis of the surface of the copper plating on the treated PTFE, it is confirmed that the hydrophilic surface of the treated film contributes to uniform copper plating.