Electrospray ionization for deposition of ultra-thin polymer layers – principle,electrophoretic effect and applications

Nebulizing of polymer solutions, in a high-voltage field under atmospheric conditions by electrospray ionization (ESI), is a comfortable way to deposit ultra-thin layers of polar or ionic polymers onto any conductive substrate materials. The substrate is grounded and the polymer solution is sprayed through a powered capillary. The formed charged droplets shrink by solvent evaporation during their way to the grounded substrate, the charges close ranks and the droplets collapse consecutively by charge repulsion, thus forming finally charged single macromolecules. After their discharging at the grounded substrate, an ultra-thin ‘quasi-monomolecular’ polymer layer is formed. It could be shown by imaging of scratches through the polymer layer by atomic force microscopy that the deposited polymer layers are dense at a thickness of about 10?nm. Carbon fibre bundles were coated with poly(allylamine) (PAAm) or poly(acrylic acid) (PAA) as potential adhesion-promoting layers in fibre–polymer composites. The polymer deposition is self-inhibiting after formation of a continuous coverage of about 200?nm for PAAm and 30?nm for PAA as result of surface charging. Continuous deposition onto such isolating layers or polymers without charging can be achieved by using current of alternating polarity. The film formation is self-healing because of the electrophoretic effect, i.e. the ion discharging occurs preferentially at non-coated areas. This electrophoretic effect of ESI was demonstrated by completely enwrapping all the carbon fibres of the roving within a distance of about 100?μm far from its outside and also at the backside of the fibre bundle with about 80% of the topside coverage, as measured by X-ray photoelectron spectroscopy and visualized using scanning electron microscopy.     

Synthesis of poly(acrylic acid) grafted carbon black and its application for sensing ethanol

Surface initiated reversible addition-fragmentation chain transfer (RAFT) polymerization techniques have been used to produce poly (acrylic acid) (PAA)-grafted carbon black (CB) nanoparticles. The surface of CB nanoparticles was functionalized in the presence of CB-supported macroRAFT agents. The resultant CB-g-PAA composites were characterized by Fourier transformed infrared spectra, thermal gravimetric analysis and energy dispersive spectrometry. The composites were dip-coated on epoxy resin electrodes to prepare novel thin film gas sensors, and the electrical responses of sensors towards ethanol were investigated. It was found that the sensors exhibited positive correlation electrical response towards ethanol vapor.     

Electrical properties of sorbitol‐doped poly(vinyl alcohol)–poly(acrylamide‐co‐acrylic acid) polymer membranes

Solid polymer membranes from poly(vinyl alcohol) (PVA) and poly(acrylamide‐co‐acrylic acid) (PAA) with varying doping ratios of sorbitol were prepared using the solution casting method. The films were examined with Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and AC impedance spectroscopy. The impedance measurements showed that the ionic conductivity of PVA–PAA polymer membrane can be controlled by controlled doping of sorbitol within the polymer blends. The PVA–PAA–sorbitol membranes were found to exhibit excellent thermal properties and were stable for a wide temperature range (398–563K), which creates a possibility of using them as suitable polymers for device applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Tuned interactions of silver nanoparticles with ZSM-5 zeolite by adhesion-promoting poly(acrylic acid) deposited by electrospray ionization (ESI)

The electrospray ionization (ESI) method was used for deposition of thin films of poly(acrylic acid) (PAA) on Cu/ZSM-5 (5 wt.% Cu) and Ag–Cu/ZSM-5 (1 wt.% Ag and 4 wt.% Cu) composites. For comparative purposes, the ZSM-5 zeolite was synthesized under hydrothermal conditions and loaded with PAA under the same treating conditions as the composites. This method allowed the formation of uniform polymer films of controlled thickness on conductive substrates. The structural characteristics were characterized by X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, atomic force microscopy and X-ray diffraction (XRD). The deposited PAA layer over ZSM-5 acts as a common dispersing and stabilizing agent through coordination-driven guest-templated polymer via interaction of Ag⁺ and Cu²⁺ with carboxylic acid groups, thus increasing and controlling the adhesion and the release of metallic species. A short exposure to light and temperature has reduced the metal ions to Cu⁰ and Ag⁰ metallic nanoparticles. The results of XRD analysis let suggest that the interaction of Cu and Ag with carboxylic groups of PAA inhibits the formation of large metallic silver particles. These samples were being studied for their potential as antibacterial agents toward the bacterial strains such as Staphylococcus pneumonia, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa as Gram positive and Gram negative bacteria, respectively. Aspergillus fumigatus and Candida albicans as Fungi were also evaluated. The Cu/ZSM-5 and Ag–Cu/ZSM-5 nanocomposites coated with a 10 nm thick PAA layer exhibit significant antibacterial activity.     

Effects of poly(acrylic acid) and poly(ethylene oxide) adsorption on the stability of alumina suspension

The effect of adsorbed polymer on the stability of alumina suspension was investigated. Poly(ethylene oxide) (PEO), poly(acrylic acid) (PAA) and similar kinds of polymer salts were used as a dispersant. The amount of polymer adsorbed on alumina surface and the suspension stability was measured. The pH, molecular weight, and concentration were considered as experimental parameters. PEO shows low affinity on the alumina surface while PAA has high affinity. In the case of PAA adsorption, the surface charge change by polymer adsorption influences suspension stability strongly, but not in the case of PEO adsorption. In simultaneous adsorption of PEO and PAA, the PAA concentration was fixed and PEO concentration was varied. The stability of suspension increased with increasing PEO concentration, and this is partly due to the steric stabilization by adsorption of PAA-PEO complex or adsorption of PEO through pre-adsorbed PAA and the depletion effect of non-adsorbed polymer. Suspension adsorbing sodium salts of PAA and poly(methacrylic acid) (PMA) each showed similar stability. But, when the PEO and these kinds of salts were added together to the suspension, the one with PAA sodium salt could keep a higher stability even with lower molecular weights of PEO compared with suspension with PMA sodium salt.     

Transport of ionizable drugs and proteins in crosslinked poly(acrylic acid) and poly(acrylic acid-co-2-hydroxyethyl methacrylate) hydrogels. I. Polymer characterization

The purpose of this investigation was to define the polymer structure and elucidate the swelling behavior of ionizable hydrophilic polymers (hydrogels) in water and buffered media. Poly(acrylic acid) (PAA) and poly(acrylic acid-co-2-hydroxyethyl methacrylate) [P(AA-co-HEMA)] hydrogels were synthesized with varying degrees of hydrophilicity and crosslinking and were designed as potential bioadhesive controlled-release dosage forms. The thermal initiation procedure employed during polymerization was optimized to eliminate unreacted residuals. Equilibrium and dynamic swelling studies were undertaken to determine the polymer mesh size and molecular weight between crosslinks of the hydrogels in the ionized and nonionized states. The PAA hydrogel mesh sizes ranged from 100 to 400 Å over pH values of 3–7, whereas the P(AA-co-HEMA) hydrogel mesh sizes were between 13 and 140 Å. These results demonstrated the significance of the swelling medium pH on the hydrated state of the polymers relative to crosslinking or copolymerization composition. © 1996 John Wiley & Sons, Inc.     

A mucoadhesive polymer prepared by template polymerization of acrylic acid in the presence of poly(ethylene glycol) macromer

A new mucoadhesive polymer complex was prepared by the template polymerization of acrylic acid with poly(ethylene glycol) macromer (PEGM) as a template polymer. Fourier transform infrared results showed that the poly(acrylic acid) (PAA)/PEGM mucoadhesive polymer complex was formed by hydrogen bonding between the carboxyl groups of PAA and the ether groups of PEGM. The glass‐transition temperature of the PAA/PEGM mucoadhesive polymer complexes was shifted to a lower temperature as the repeating unit ratio of PAA/PEGM in the complex decreased. The dissolution rate of the PAA/PEGM mucoadhesive polymer complex was much slower than that of the PAA/poly(ethylene glycol) (PEG) mucoadhesive polymer complex and was dependent on the pH and molecular weight of PEGM. The mucoadhesive force of the PAA/PEGM mucoadhesive polymer complexes was stronger than that of commercial Carbopol 971P NF and almost the same as that of the PAA/PEG mucoadhesive polymer complex. The PAA/PEGM interpolymer complex seemed to be a better mucoadhesive polymer matrix than the PAA/PEG interpolymer complex. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1904–1910, 2002     

Architectural effect of poly(acrylic acid) and poly(amide imide) block copolymers on dispersion of carbon nanotubes in water

The dispersion of carbon nanotubes (CNTs) in water by poly(acrylic acid) (PAA) and poly(amide imide) (PAI) block copolymers and homo‐PAA is investigated. Poly(acrylic acid)‐block‐poly(amide imide) (PAA‐block‐PAI), poly(acrylic acid)‐block‐poly(amide imide)‐block‐poly(acrylic acid) (PAA‐block‐PAI‐block‐PAA), and heteroarm star block copolymer poly(acrylic acid)₂poly(amide imide) (PAA₂PAI) with similar molecular weights and PAA contents are used as the copolymers. The dispersion of CNTs is observed by dynamic light scattering and ultraviolet‐visible spectroscopy. The presence of the hydrophobic sequence improves the dispersion. PAA₂PAI has the best dispersion ability, followed in order by PAA‐block‐PAI‐block‐PAA, PAA‐block‐PAI, and homo‐PAA. In the dry state, aggregates of CNT are observed by transmission electron microscopy (TEM) in the mixture with PAA‐block‐PAI and homo‐PAA. The adhesion of the copolymers to CNT is also observed by TEM and is due to the high affinity between hydrophobic PAI and CNT. In particular, PAA₂PAI and PAA‐block‐PAI‐block‐PAA well cover the CNTs. The presence of PAI and the PAA location are important for the dispersion of CNTs. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43461.     

Swelling of thermosensitive interpenetrating polymer networks composed of poly(vinyl alcohol) and poly(acrylic acid)

The swelling behavior of interpenetrating polymer networks (IPNs) composed of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) in water was studied. The PVA/PAA IPN gels were prepared by four synthetic methods. The swelling behaviors of these IPNs made by different methods were compared. The differences in swelling behaviors of samples are discussed on the basis of their structural and physical differences. © 1996 John Wiley & Sons, Inc.     

Study of the interaction of poly(acrylic acid) and poly(acrylic acid‐poly acrylamide) complex with bone powders and hydroxyapatite by using TGA and DSC

The thermo gravimetric analysis (TGA) and differential scanning calorimetric analysis (DSC) were used to study the thermal degradation of poly(acrylic acid) PAA and poly(acrylamide) PAAm as well as the compound obtained from their interactions. The examination of the thermal curves revealed that the characteristics of the curves of the compound resulting from the cooperative interactions are different from those of the constituent polymers. The differences in the characteristics of the thermal curves were attributed to the formation of an interpolymer complex resulting from the interaction of PAA with PAAm at low pH value. These two thermal techniques were also used to investigate the thermal behavior of the compounds obtained from the interaction of PAA and (PAA‐PAAm) mixture with bone powders (BP) and hydroxyapatite (HA). It was found that the TGA, DTG, and DSC curves do not show the peak of formation and degradation of PAA anhydride which provided strong evidence for the consumption of PAA in the reaction between the polymer and BP. The interaction between PAA and the thermally treated BPs and HA was investigated. Moreover the interaction between the mixture of PAA and PAAm at different pH values and the BPs and HA was discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Grafting of poly(acrylic acid) onto cellulosic microfibers and continuous cellulose filaments and characterization

Results from the grafting of poly(acrylic acid) (PAA) onto cellulosic microfibers and continuous cellulose filaments are presented. The grafting of PAA onto cellulosic fibers offers the possibility of developing enhanced ion exchange and fluid absorbency on the fibers. The grafting of PAA was carried out with a two‐step procedure. First, vinyl‐terminated ethoxy silane was deposited on the surface of the fiber. This was followed by a grafting polymerization reaction in aqueous media of acrylic acid with different concentrations of potassium persulfate (KPS), which acted as the initiator. The percentage of grafting increased with increasing KPS concentration and reached a maximum value at a concentration of about 0.4 wt % with respect to the weight of the fiber. The grafted copolymer was characterized by Fourier transform infrared spectroscopy. Strong evidence that the grafting reaction was successful was given by the presence of a band, with a maximum at 1732 cm^?1, that was characteristic of carbonyl group absorption and was not initially present in the cellulosic fibers. The water absorption of the cellulosic microfibers grafted with PAA was three times greater than the water absorption of the nongrafted microfibers. The mechanical properties of continuous cellulose filaments did not change drastically with PAA grafting. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 386–393, 2002     

Synthesis of thermoresponsive poly(N-isopropylmethacrylamide) and poly(acrylic acid) block copolymers via post-functionalization of poly(N-methacryloxysuccinimide)

Polymers exhibiting a thermoresponsive, lower critical solution temperature (LCST) phase transition have proven to be useful for many applications as “smart” or “intelligent” materials. A series of poly(N-isopropylmethacrylamide) (PNIPMAM) polymer, poly(N-isopropylmethacrylamide)-b-poly(acrylic acid) (PNIPMAM-b-PAA) diblock, and poly(acrylic acid)-b-poly(N-isopropylmethacrylamide)-b-poly(acrylic acid) (PAA-b-PNIPMAM-b-AA) triblock copolymer samples were synthesized via ATRP. A facile post-functionalization route was developed that uses an activated ester functionality to convert poly(N-methacryloxysuccinimide) (PMASI) blocks to LCST capable polyacrylamide, while poly(t-butyl acrylate) (PtBA) blocks were converted to water-soluble poly(acrylic acid) (PAA). The post-functionalization was monitored via ¹H NMR and ATR-FTIR. The aqueous solution properties were explored and the PNIPMAM polymers were shown to have a LCST phase transition varying from 35 to 60 °C. The ability to synthesize block copolymers that are thermoresponsive and water-soluble will be of great benefit for broader applications in drug delivery, bioengineering, and nanotechnology.     

Properties of carbon fiber sized with poly(phthalazinone ether ketone) resin

We studied thermoplastic poly(phthalazinone ether ketone) (PPEK) resin as a sizing agent on carbon fiber, with emphasis on its thermal stability, surface energy, wetting performance, and interfacial shear strength (IFSS). X‐ray photoelectron spectroscopy characterization was carried out to study the chemical structure of sized/unsized carbon fibers. Scanning electron microscopy and atomic force microscopy were used to characterize surface topography. TGA was used to analyze the thermal stability. Meanwhile, contact angle measurement was applied to analyze the compatibility between the carbon fibers and PPEK and the surface energy of carbon fibers. IFSS of carbon fiber/PPEK composite was examined by microbond testing. It is found that carbon fibers uniformly coated with PPEK resin had better thermal stability and compatibility with PPEK resin than the uncoated fiber. The contact angle is 57.01° for sized fibers, corresponding to a surface energy of 49.96 mJ m^?2, much smaller than that for unsized ones with contact angle value of 97.05°. The value of IFSS for sized fibers is 51.49 MPa, which is higher than the unsized fibers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Blends of polybenzoxazine/poly(acrylic acid): hydrogen bonds and enhanced performances

This work focuses on exploring the role of the additional hydrogen bond donor moiety‐containing polymer poly(acrylic acid) (PAA) in the hydrogen bonds and properties of polybenzoxazines. Thorough studies showed that PAA could not only decrease the curing temperature of benzoxazine resin, but also give additional hydrogen bond donors that were beneficial to the hydrogen bonding interactions and performances of polybenzoxazine/PAA blends. As the hydrogen bonds varied, the glass transition temperature and tensile modulus of the polymer blends changed in accordance with the hydrogen bonds. The results revealed that the introduction of the hydrogen bond donor moiety‐containing polymer was beneficial for hydrogen bonding interactions, which could improve the performances of polybenzoxazines. This novel insight is anticipated to be of help to researchers in the development of more polybenzoxazines and polybenzoxazine blends with enhanced properties. © 2017 Society of Chemical Industry     

PH-induced structure change of poly(vinyl alcohol) hydrogel crosslinked with poly(acrylic acid)

The structure of the hydrogel of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) was investigated by small angle X-ray scattering (SAXS) of synchrotron radiation. A physically crosslinked blend gel, which was prepared by repetitive freezing and thawing of an aqueous solution of PVA and PAA, could be chemically crosslinked by esterfication of PVA with PAA even in the hydrogel state. The chemical crosslinking induced the destruction of physical crosslinks into a folded structure, indicating that the chemical crosslinking proceeds at the sites around the physical crosslinks that contain PVA and PAA in much higher concentration than other portion of the gel. The pH-induced structure changes of the PVA hydrogels, chemically crosslinked with poly(acrylic acid) (PAA) were investigated by SAXS on the samples of various chemical crosslinking time. The gels were shrunk at pH4, and swollen at pH8. The results of SAXS showed, that the Porod slope changed with chemical crosslinking time from -3.5 to ?2.9 at pH4, and from ?2.9 to ?2.4 at pH8. The results suggest that a folded structure as a structural domain, which is characterized by fractally rough interface, tends to change into the structure that corresponds to percolation cluster, particularly at pH8. The gels immersed in pH8 showed a remarkable structure change accompanying swelling. The results revealed that a conformational change of PAA chains, induced by the pH change, can be explained by the presence of a structural domain in the gel network, where both PVA chains and PAA chains get entangled and partially form a interpenetrating polymer network(IPN).     

Graphite fiber-epoxy interphase modification by electrodeposition of poly(styrene-co-maleic anhydride) and its influence on composite properties

An electrodeposition technique has been used for the modification of the fiber-matrix interphase in graphite fiber-epoxy composites. A coating of poly(styrene-co-maleic anhydride) (SMA) polymer was electrodeposited from an aqueous solution on AU graphite fibers used as electrodes in an electrolytic cell. Different electrocoating parameters were initially used to establish the optimum conditions to achieve thin uniform coatings suitable for functioning as interphases in composites reinforced by the coated fibers. The interfacial shear strength (IFSS), evaluated by a single-fiber composite technique, showed that the SMA coating resulted in an improvement of about 50% in IFSS compared with the commercially treated fibers (AS). This was achieved without sacrificing impact strength. Evidence of good epoxy penetration into the coating was obtained by the use of electron microprobe line scans for bromine across the diameter of a filament in a single fiber composite-the bromine introduced through the use of a brominated epoxy resin. The observed improvement in the fiber-matrix interfacial shear strengths is dependent on the co-monomer ratio in electrodeposited SMA.     

A novel mucoadhesive polymer prepared by template polymerization of acrylic acid in the presence of poly (ethylene glycol)

A new mucoadhesive polymer was prepared by template polymerization of acrylic acid in the presence of poly(ethylene glycol) (PEG). FTIR results indicated that a polymer complex was formed between poly(acrylic acid) (PAA) and PEG through hydrogen bonding. The hydrogen bonding in the PAA/PEG polymer complex was stronger than that in the PAA/PEG blend, and became stronger as the molecular weight of PEG increased. Glass transition temperatures (T_g) of PAA in the PAA/PEG polymer complexes was shifted to a lower temperature than that of PAA in the PAA/PEG blend. However, they tended to become higher as the molecular weight of PEG increased. The dissolution rate of the PAA/PEG polymer complex was much slower than the PAA/PEG blend, and was dependent on pH and molecular weight of the PEG. The mucoadhesive force of the PAA/PEG polymer complexes was stronger than for the PAA/PEG blend or a commercial product, Carbopol 971P NF. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2749–2754, 1999     

Infrared spectroscopy and electrical properties of ternary poly(acrylic acid)–metal–poly(acrylamide) complexes

Fourier transform infrared spectroscopy (FTIR) and electrical measurements were used for the characterization of the interpolymer complexation between poly(acrylic acid) (PAA) and poly(acrylamide) (PAAm) and also the ternary PAA–metal–PAAm complexes. The interpolymer complexes were prepared by adjusting the pH value of the mixture solutions at different PAA weight fractions (W_PAA). The ternary complexes were prepared by mixing metal chloride solutions (such as ErCl₃ and LaCl₃) with different concentrations to PAA–PAAm mixtures and adjusting the pH value for different W_PAA. It was found that the IR spectra of the interpolymer complexes showed absorption bands at shifted positions and of intensities different from those of the parent polymers. Also, the examination of the spectra of the ternary metal–polymer complexes revealed that they depend on the nature, lency, ionic radius, and concentration of the added metal chlorides. Analysis of the electrical results showed that the electrical conductivity of the interpolymer complexes are always lower than those of PAA and PAAm, which was attributed to the decrease in the mobility of the polymer chains as a result of the complexation. Also, the conductivity of the ternary metal complexes showed a dependence on the properties of the additives and were found to decrease with increasing their concentrations. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2699–2705, 2002     

Grafting of the acrylic acid on poly(ethylene terephthalate)

A study has been made of the effect of solvent nature, concentrations of monomer, initiator and homopolymerization inhibitors, and initial polymer structure on the modification of poly(ethylene terephthalate) (PET) films and fibers by grafting the acrylic acid (AA). AA grafting initiated by radicals formed from thermal decomposition of benzoyl peroxide. It has been established that preswelling of PET in dichloroethane leads to changes in its sorption–diffusion properties and favors an increase in the degree of grafting. Addition of the Fe(II), Ni(II), and Cu(II) salts to AA solution decreased homopolymer yield. The studied process of grafting can be described by equations of diffusion kinetics. Distribution of the poly(acrylic acid) (PAA) over the cross section of samples and a number of physical and chemical properties depend also on conditions of performing the graft polymerization.     

Study of ternary component polymer complexes of poly(methacrylic acid) and poly(acrylic acid) with complementary polymers

Ternary component polymer complexes have been prepared from poly(acrylic acid) and poly(methacrylic acid) with complementary polymers, such as poly(vinylpyrrolidone) and poly(ethylene oxide). The formation of ternary complexes, selective complexation, and mutual compatibility of the complementary polymers attached to the same polycarboxylic acid chain, have been studied by several techniques, such as viscometry, turbidimetry, potentiometry, conductometry, and IR spectra.