ATR-FTIR Studies Research Articles

Surface modification of commercial polyamide reverse osmosis membranes by radical grafting: An ATR-FTIR study

A new grafting procedure was developed for surface modification of commercial polyamide reverse osmosis membranes. Acidic and neutral acrylic monomers and sulfo-containing vinyl monomers were successfully grafted from aqueous solutions under mild conditions. The modifications were monitored by ATR-FTIR spectra. The characteristic peaks of functional groups introduced by grafting were evaluated. The spectral findings correlated with physicochemical properties of the membranes.

FTIR-ATR study of self-assembled thiol monolayers on gold

Self-assembled monolayers of 1-teradecanethiol on gold were characterized by means of FTIR-ATR measurements, XPS and contact angle measurements. Linear dichroism measurements using FTIR-ATR are used to estimate the orientation of the alkyl chains. An equation for calculating the orientation angles of the alkyls chains was deduced.

A voltammetric and FTIR–ATR study of the electropolymerization of phenol on platinum electrodes in carbonate medium

Abstract Voltammetry and FTIR–ATR techniques have been employed to investigate polyphenol films formed on platinum surfaces by electrochemical oxidation of phenol. The media used in the electropolymerization were aqueous carbonate solutions, with and without Na 2 S. The polymeric films created are not permeable to ferrocyanide and ferricyanide species and present low water mobility. The presence of sulfide in the electropolymerization solution enhances these characteristics. The amount of sulfur detected by an energy dispersive X-ray detector (EDX) in the polymeric films created in the presence and in the absence of sulfide in the solution is very similar. Thus, the sulfur present in the polymer created in solutions with a sulfide concentration up to 10 −3 M is not representative. A strong stretching vibration band at 900–1150 cm −1 is obtained in the IR spectrum that can be associated to the ether linkages of the phenolic rings (COC).

Anin-situ ATR-FTIR study on polyelectrolyte multilayer assemblies on solid surfaces and their susceptibility to fouling

In-situ attenuated total reflection (ATR)-FTIR spectroscopy was used to monitor the consecutively alternating adsorption of polyethylenimine (PEI) and poly(acrylic acid) (PAC) onto both Si crystals (SiO) and CO2 plasma-treated polypropylene (PP) films. The vibration band vas(COO−) and v(CO) of PAC are diagnostic for the polyelectrolyte layer build-up and sensitive to protonation changes. Human serum albumine (HSA) adsorption experiments revealed a strong decrease of fouling for the PP films, which were modified with polyelectrolyte multilayers, in comparison to the unmodified ones.

ATR-FTIR and SEM Gradient Study of Poly(2-ethylhexyl acrylate)/Poly (vinylidene fluoride-co-hexafluoro acetone) Blends

The segregation structure and the gradient structure of poly(2-ethylhexylacrylate) (P2-EHA)/poly(vinylidene fluoride-co-hexafluoro acetone) [P(VDF-HFA)] blends were confirmed by ATR-FTIR and SEM. For the P2-EHA/P(VDF-HFA) (50/50) blend, the P(VDF-HFA) and P2-EHA layers were observed at the free surface side and bottom side, respectively. The gradient structure was obtained for the P2-EHA/P(VDF-HFA) (30/70) blend. The domain morphology of a cross section of the P2-EHA/P(VDF-HFA) (50/50) blend was dramatically changed by the thickness of the blend film. Finally, we propose that the segregation structure and gradient structure formed in P2-EHA/ P(VDF-HFA) blends were caused by surface tension difference, rate of phase separation, rate of solvent evaporation, and molecular weight difference.

ATR-FTIR studies of ionic solvation and ion-pairing in dimethyl sulfoxide solutions of the alkali metal nitrates

Ionic solvation and ion pairing were studied in solutions of lithium, sodium and potassium nitrate in dimethyl sulfoxide, using ATR-FTIR spectroscopy. Ion-pairing constants and apparent solvation numbers were estimated over a wide range of concentrations. Dimerization of the solvent was taken into account. The results obtained are discussed with respect to the electrolyte concentration and the properties of the cations of the electrolyte.

Mechanisms of buccal mucoadhesion of novel copolymers of acrylic acid and polyethylene glycol monomethylether monomethacrylate

A series of novel mucoadhesive copolymers of acrylic acid and poly (ethylene glycol) monomethylether monomethacrylate [P(AA-co-PEG)] were designed, synthesized, and characterized for optimization of buccal mucoadhesion. The mechanisms of mucoadhesion of these copolymers were investigated using surface energy analysis, mucoadhesive force measurements, and FTIR studies. The surface energy was analyzed based upon interfacial energy in a three phase (hydrogel, interstitial fluid, mucus) system. Individual spreading coefficients were combined to give a single parameter called combined spreading coefficient ( S C), which was used as a predictive measure for mucoadhesive performance. A good correlation between predicted mucoadhesive performance and measured mucoadhesive force was found. To achieve spontaneous intimate contact between polymer and buccal mucosa, surface properties were optimized for buccal adhesion by varying the composition of the copolymers. The surface property of the copolymers for mucoadhesion was optimized by introducing PEG into PAA. ATR-FTIR studies revealed that formation of hydrogen bonds as compared to PAA was enhanced through the incorporation of the PEG moiety. It was found that the mole ratio of the repeat units of PEG (ethylene glycol) to AA in these copolymers is of great importance for the mucoadhesive process. From this investigation, it was concluded that surface energy effects and spreading processes play a dominant role for the mucoadhesive performance.

FTIR-ATR studies of interfacial interactions in epoxy resin/polymer laminate structures

FTIR-ATR spectroscopy has been used to investigate the interdiffusion of acrylic or alkyd-based polymer coatings with an epoxy resin underlayer. It has been shown that there is considerable penetration on a short (hours) time scale and that strong hydrogen-bonding interactions occur between top coat and resin. It has also been shown that a trimeric isocyanate diffuses into the epoxy resin film and that this process depends on the degree of cross-linking of the resin. These data have important implications for the design and use of paint and other industrial coatings.

Characterization of LLDPE-LLDPEgMA Blends by Contact Angle and FTIR-ATR Studies

Blends of linear low-density polyethylene (LLDPE) and linear low density polyethylene-grafted maleic anhydride (LLDPEgMA) were prepared by melt mixing. The surface of cast films with overall contents of 0 to 100 wt% of maleated LLDPE were characterized through contact angle measurements as well as attenuated total reflection infrared spectroscopy (FTIR-ATR). The contact angles of water and dimethylformamide (DMF) on cast film surfaces of LLDPE/LLDPEgMA blends decreases when the modified polymer content increases. From FTIR-ATR spectras of the blends, the carbonyl index on the films' surface was calculated. It was found that the higher the carbonyl index, the lower the contact angle value for the polyethylene blends. The roughness of the cast and extruded reference films was also analyzed using atomic force microscopy (AFM).

Abstract

A series of novel mucoadhesive copolymers of acrylic acid and poly (ethylene glycol) monomethylether monomethacrylate [P(AA-co-PEG)] were designed, synthesized, and characterized for optimization of buccal mucoadhesion. The mechanisms of mucoadhesion of these copolymers were investigated using surface energy analysis, mucoadhesive force measurements, and FTIR studies. The surface energy was analyzed based upon interfacial energy in a three phase (hydrogel, interstitial fluid, mucus) system. Individual spreading coefficients were combined to give a single parameter called combined spreading coefficient (SC), which was used as a predictive measure for mucoadhesive performance. A good correlation between predicted mucoadhesive performance and measured mucoadhesive force was found. To achieve spontaneous intimate contact between polymer and buccal mucosa, surface properties were optimized for buccal adhesion by varying the composition of the copolymers. The surface property of the copolymers for mucoadhesion was optimized by introducing PEG into PAA. ATR-FTIR studies revealed that formation of hydrogen bonds as compared to PAA was enhanced through the incorporation of the PEG moiety. It was found that the mole ratio of the repeat units of PEG (ethylene glycol) to AA in these copolymers is of great importance for the mucoadhesive process. From this investigation, it was concluded that surface energy effects and spreading processes play a dominant role for the mucoadhesive performance.

Modifications induced on stratum corneum structure after in vitro iontophoresis: ATR-FTIR and X-ray scattering studies

The aim of the present work was to investigate stratum corneum (s.c.) structure after prolonged in vitro iontophoresis by two physical techniques: ATR-FTIR and X-ray scattering. ATR-FTIR studies showed that iontophoresis induced an important and reversible increase in the hydration of the outer layers of s.c. but no increase in lipid fluidity could be detected. SAXS (small angle X-ray scattering) of s.c. showed that iontophoresis induced a disorganisation of the lipid layers stacking reversible within a few days. No modification of the intralamellar crystalline packing of lipids nor of keratin were observed by WAXS (wide angle X-ray scattering). From our ATR-FTIR and X-ray scattering observations, it can be assumed that the enhancement in transdermal permeation which characterizes iontophoresis is related to the lipid layer stacking disorganisation.

Coassembly of synthetic segments of shaker K+ channel within phospholipid membranes.

Increasing evidence suggests that membrane-embedded hydrophobic segments can interact within the phospholipid milieu of the membrane with varying degrees of specificity and thus contribute to the folding and oligomerization of proteins. We have used synthetic peptides corresponding to segments from the hydrophobic core of the Shaker potassium channel as a model system to study interactions between membrane-embedded segments. Three synthetic segments of the Shaker K+ channel, comprising the hydrophobic S2, S3, and S4 sequences, were used, and their secondary structure, their interactions with, and orientation within phospholipid membranes were examined. Secondary structure studies revealed that though S3 and S4 both adopt certain fractions of alpha-helical structures in membrane mimetic environments, the alpha-helical content of S3 is lower. Both S3 and S4 bind strongly to zwitterionic phospholipids, with partition coefficients in the order of 10(4) and 10(5) M-1. ATR-FTIR studies showed that while the S4 peptide is oriented parallel to the membrane surface, S3 tends to a more transmembranal orientation. Enzymatic cleavage experiments demonstrated that the presence of S3 induces some change in the proteolytic accessibility of the S4 segment. Resonance energy transfer measurements, done in high lipid/peptide molar ratios, revealed that S3 and S4 cannot self-associate in zwitterionic phospholipid vesicles but can associate with each other and with the S2 segment of the channel. Furthermore, S3 does not interact with the homologous S4 region from the first repeat of the eel sodium channel, demonstrating specificity in the interactions. These results are in line with data indicating that functionally important interactions indeed exist between the negatively charged S2 and S3 regions and the positively charged S4 region [Papazian, D. M., et al (1995) Neuron 14, 1293-1301; Planells-Cases, R., et al. (1994) Proc. Natl. Acad. Sci. U.S.A. 92, 9422-9426]. From a broader point of view, these results provide further support to the notion that interactions (either specific or nonspecific) may exist between transmembrane segments of integral membrane proteins and therefore can contribute to their assembly and organization.

Changes of biofilm properties in response to sorbed substances - an FTIR-ATR study

Biofilms play an important role as sorbents in the process of distribution of pollutants in surface water systems. The sorption properties of biofilms will influence the kind and the amount of sorbed substances. The heterogeneity of biofilms provides different sorption sites which exhibit a different sorption preference and capacity. As dynamic systems, biofilms will respond physiologically to their environment. Thus, the sorption of one substance may lead to a change in the composition of the EPS or other biofilm components and further alter the original sorption properties. In this paper, the influence of toluene on a biofilm was investigated. As a suitable method, FTIR-ATR spectroscopy was applied. The method is non destructive and allows the observation of biofilm formation and behaviour on line and in situ. A biofilm was allowed to form in ATR flow-through cells. The test strain was genetically engineered and contained a bioluminescent reporter gene which was switched on when toluene was metabolized. Thus, the degree of toluene degradation activity could be observed with great sensitivity. The FTIR spectrometer contained three flow-through cells which could be operated in parallel: one was run with sterile medium only, one with medium and bacteria, and one with medium, bacteria and toluene. This arrangement allowed the discrimination of the biofilm response from other effects. The IR spectrum showed specific bands of proteins, polysaccharides, phosphoryl compounds and other groups of molecules. A significant increase of EPS-polysaccharide formation was observed at a toluene level of 5 mg L−1. At 15 mg L−1, significantly more carboxyl groups were formed. Thus, the effect of the lipophilic organic pollutant toluene increased the amount of negatively charged groups and, consequently, the sorption capacity for metal cations. This result indicates that biofilms respond in a complex manner to different sorbates and alter their environmental properties.

Changes of biofilm properties in response to sorbed substances - an FTIR-ATR study

Biofilms play an important role as sorbents in the process of distribution of pollutants in surface water systems. The sorption properties of biofilms will influence the kind and the amount of sorbed substances. The heterogeneity of biofilms provides different sorption sites which exhibit a different sorption preference and capacity. As dynamic systems, biofilms will respond physiologically to their environment, Thus, the sorption of one substance may lead to a change in the composition of the EPS or other biofilm components and further alter the original sorption properties. In this paper, the influence of toluene on a biofilm was investigated. As a suitable method, TFIR-ATR spectroscopy was applied. The method is non destructive and allows the observation of biofilm formation and behaviour on line and in situ. A biofilm was allowed to form in ATR flow-through cells. The lest strain was genetically engineered and contained a bioluminescent reporter gene which was switched on when toluene was metabolized. Thus, the degree of toluene degradation activity could be observed with great sensitivity. The FTIR spectrometer contained three flow-through cells which could be operated in parallel: one was run with sterile medium only, one with medium and bacteria, and one with medium, bacteria and toluene. This arrangement allowed the discrimination of the biotllm response from other effects. The IR spectrum showed specific bands of proteins, polysaccharides, phosphoryl compounds and other groups of molecules. A significant increase of EPS-polysaccharide formation was observed at a toluene level of 5 mg L-1, At 15 mg L-1 significantly more carboxyl groups were formed. Thus, the effect of the lipophilic organic pollutant toluene increased the amount of negatively charged groups and, consequently, the sorption capacity for metal cations. This result indicates that biofitlms respond in a complex manner to different sorbates and alter their environmental properties.

FTIR-ATR study of the co-adsorption of benzophenone with sodium dodecyl sulfate and sodium dodecylbenzenesulfonate using Al 2O 3-coated optics

The adsorption of sodium dodecyl sulfate (SDS) and sodium dodecylbenzenesulfonate (SLABS), and the co-adsorption of those surfactants with a “probe” species — benzophenone (BPN) — at the Al 2O 3/aqueous solution interface were examined via polarized Fourier transform infrared (FTIR) attenuated total reflection (ATR) spectroscopy. The internal reflection element (IRE) was ZnSe, coated with 0.1–0.25 μm of Al 2O 3 deposited by r.f. sputtering. This technique allows in situ determination of adsorption isotherms and adsorbate structures from IR-ATR spectra of the surfactants. Spectra of the surfactant head groups may be analyzed at energies down to about 900 cm −1. The interface remains in contact with surfactant solution while the spectra are obtained. Solvation-induced band shifts for BPN co-absorbed with SDS or with SLABS, compared with band positions in various solvents, indicated that BPN resided in the alkyl region of the SDS or SLABS surface layer. The extent of co-adsorption was a function of pH and ionic strenght. The presence of the BPN reduced the adsorption density of both SDS and SLABS. Orientation of the probe molecules within the adsorbed SDS layer was determined from the linear dichroic ratios exhibited by polarized ATR spectra. The orientation of the BPN molecules changed significantly with solution conditions, but generally the long axis of the BPN molecules was normal to long axes of the surfactant alkyl chains. The surfactant alkyl chains were found to be inclined to the surface normal at angles of 42–50, and the phenyl rings of SLABS were inclined at 38–45, depending upon the conditions. The implications of these results for the IR spectral analysis of adsorbate structures are discussed.

FTIR‐ATR studies of drawing and poling in polymer bilaminate films

AbstractA large increase in the remnant polarization of drawn and poled poly(vinylidene fluoride) (PVF2)/nylon 11 bilaminates compared with the individual films observed in other studies provides the motivation for the examination of dipole orientation in variously treated single and bilaminate films with FTIR‐ATR spectroscopy. Four ATR spectra are collected from each surface using two sample orientations and two light polarizations for each incident light angle. The incident light angle is varied to obtain information about the change in structure with depth. Computer simulations of the experimental optics using anisotropic optical constants aides in the interpretation of experimental results. As the result of simple one‐way drawing in PVF2 and nylon 11, anisotropy in dipole orientation is observed in the plane transverse to the draw direction. In both single and bilaminate films, the average direction of the amide plane in nylon 11 and the CF2 dipoles in PVF2 resides in the plane of the film, perpendicular to the subsequent poling field direction as a result of one‐way drawing. The transverse plane orientation is depth dependent in nylon 11 in both single and bilaminate films and is attributed to a surface‐induced effect. Poling fields of 1.6 MV/cm produce large differences between the surfaces of single films and the bilaminates. At the interior interface of the drawn and poled bilaminates, the PVF2 and nylon 11 dipoles important in polarization appear to be random. The structural implications of this as well as other observations from the spectra are interpreted in terms of the large remnant bulk polarization in the poled bilaminate. © 1994 John Wiley & Sons, Inc.

An In-Situ ATR-FTIR Study: The Surface Coordination of Salicylic Acid on Aluminum and Iron(III) Oxides

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAn In-Situ ATR-FTIR Study: The Surface Coordination of Salicylic Acid on Aluminum and Iron(III) OxidesMadeleine V. Biber and Werner. StummCite this: Environ. Sci. Technol. 1994, 28, 5, 763–768Publication Date (Print):May 1, 1994Publication History Published online1 May 2002Published inissue 1 May 1994https://doi.org/10.1021/es00054a004RIGHTS & PERMISSIONSArticle Views1941Altmetric-Citations171LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (825 KB) Get e-Alerts Get e-Alerts

PHOTOOXIDATION OF SILOXANE POLYMERS UNDER VACUUM ULTRAVIOLET IRRADIATION

Vacuum ultraviolet(VUV) irradiation (wavelength 147 nm) of siloxane polymers in the presence of air was studied using ATR FTIR and XPS spectroscopy. The ATR FTIR study revealed the formation of CO and OH groups in the surface layer depending on irradiation time and air pressure. The concentrations of CO and OH groups level off with the increase of irradiation time and pass through the maximum value with the increase of pressure in the range of 0.1-100torr. The XPS study of irradiated polysiloxane films demonstrated that intermolecular crosslinking via oxygen atoms also takes place on the polymer surface. The concentrations of the most important oxygen species O and O3, produced by VUV photolysis of air and coming to the polymer surface were calculated for the air pressure range 0.1-100torr. The photooxidation mechanism for siloxane polymers under VUV irradiation in air has been proposed.

ATR-FTIR studies of ion–solvent and ion–ion interactions in divalent-metal perchlorate–acetonitrile solutions

The effect of divalent-metal ions on the IR spectrum of acetonitrile has been examined by studying the dependence of the spectral features on concentration for seven divalent-metal-ion perchlorates. Data are reported for both the frequency shifts and molar absorption coefficients of the major bands in acetonitrile which are affected by the presence of a cation in solution. It is shown that ion association plays a major role in determining the magnitude of the frequency shift. Other features discussed include the effect of the combination band in protonated acetonitrile, and the role of metal-ion softness in cation–acetonitrile interactions.

Infrared spectroscopic examination of the surfaces of hydrated copoly(ether-urethane-ureas)

The FTIR-ATR study show that hydration of copolymer surfaces results in an increase in the hydrogen bonding of the urethane carbonyl groups and a decrease in the hydrogen bonding of the amide nitrogens. These changes may be the result of orientational rearrangements of the functional groups in the urea domain, the interfacial urethane region, and the polyether matrix upon hydration