Fourier Transform Infrared Spectroscopy Data Research Articles

Semiconductor Surface-Induced 1,3-Hydrogen Shift: The Role of Covalent vs Zwitterionic Character

X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) are used to compare the reaction of 1,2-cyclohexanedione (1,2-CHD) with Si(001) and diamond(001) surface dimers under ultra-high-vacuum conditions. 1,2-CHD is known to undergo a keto-enol tautomerization, with the monoenol being the primary equilibrium species in the solid and gas phases. XPS and FTIR data demonstrate that 1,2-CHD reacts with diamond(001) through the OH group of the monoenol, resulting in only one O atom being bonded to the surface. In contrast, XPS and FTIR data suggest that both oxygen atoms in the 1,2-CHD molecule bond via Si-O-C linkages to the Si(001) surface dimer, and that the molecule undergoes an intramolecular 1,3-H shift. While the Si(001) and diamond(001) surfaces are both comprised of surface dimers, the diamond(001) dimer is symmetric, with little charge separation, whereas the Si(001) dimer is tilted and exhibits zwitterionic character. The different reaction products that are observed when clean Si(001) and diamond(001) surfaces are exposed to 1,2-CHD demonstrate the importance of charge separation in promoting a 1,3-H shift and provide new mechanistic insights that may be applicable to a variety of organic reactions.

Infrared spectroscopic measurement of water permeability in polymer films exposed to liquid water

The details of a method for measuring the water vapor transport rate through polymer films utilizing Fourier transform infrared spectroscopy (FTIR) are given. Water flows across one side of the membrane and a nitrogen sweep gas carries the water vapor into the flow-through cell of the spectrometer for measurement. The method was used to test two polymers that have literature values and four new polymers. The resulting FTIR data was analyzed with a partial least-squares method. Experimentally the method is easy to apply and very accurate.

Unambiguous determination of Fourier-transform infrared spectroscopy proportionality factors: The case of silicon nitride

Fourier-transform infrared spectroscopy (FTIR) analysis is a widely used tool for the analysis of bonded hydrogen in hydrogenated silicon nitride $(\mathrm{Si}{\mathrm{N}}_{x}:\mathrm{H})$. However, the proportionality factors between the integrated absorbance and bond densities, necessary for accurate hydrogen quantification, are still under discussion. The evolution of the total hydrogen concentration in thermally stable $\mathrm{Si}{\mathrm{N}}_{x}:\mathrm{H}$ during an anneal, as determined by FTIR, using previously reported proportionality factors [E. Bustarret et al., Phys. Rev. B 77, 925 (1998); W. A. Lanford and M. J. Rand, J. Appl. Phys. 49, 2473 (1978)] appears to be inconsistent with the hydrogen concentration evolution as determined by elastic recoil detection (ERD) analysis. The differences indicate invalid proportionality factors for our samples. Since annealing experiments of thermally stable $\mathrm{Si}{\mathrm{N}}_{x}:\mathrm{H}$ offer a set of samples that differ only in N-H and Si-H bond densities, recalibration of these factors can be achieved by fitting the anneal time-dependent FTIR data to the evolution curves of the hydrogen concentration as detected with ERD. In this way a fully experimental calibration tool for the N-H and Si-H FTIR proportionality factors is obtained for individual, thermally stable, alloy films with multiple configurations of hydrogen bonds. Calibration was applied to $\mathrm{Si}{\mathrm{N}}_{x}:\mathrm{H}$ films in the range $1.09lxl1.35$, deposited at high deposition rate using the hot-wire (HW) chemical vapor deposition (CVD) technique. Each film was cut into 25 samples, which were annealed for different durations at $800\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ in ${\mathrm{N}}_{2}$ and investigated using FTIR and ERD analysis. ERD measurements show that for the HWCVD $\mathrm{Si}{\mathrm{N}}_{x}:\mathrm{H}$, no detectable change in $\mathrm{N}∕\mathrm{Si}$ ratio or mass density occurs during an anneal. The thermal stability of the samples is also confirmed by FTIR measurements, where the sensitive Si-H peak position shows negligible shift during the anneal treatment. Calibration of FTIR proportionality factors for these samples shows that both proportionality factors change with the composition of the deposited films, and that they differ from reported values.

Heat-Induced Changes in Myofibrillar Protein Structures and Myowater of Two Pork Qualities. A Combined FT-IR Spectroscopy and Low-Field NMR Relaxometry Study

Low-field NMR T(2) and Fourier transform infrared (FT-IR) measurements were performed on meat samples of two qualities (normal and high ultimate pH) during cooking from 28 degrees C to 81 degrees C. Pronounced changes in both T(2) relaxation data and FT-IR spectroscopic data were observed during cooking, revealing severe changes in the water properties and structural organization of proteins. The FT-IR data revealed major changes in bands in the amide I region (1700-1600 cm(-)(1)), and a tentative assignment of these is discussed. Distributed NMR T(2) relaxation data and FT-IR spectra were compared by partial least-squares regression. This revealed a correlation between the FT-IR peaks reflecting beta-sheet and alpha-helix structures and the NMR relaxation populations reflecting hydration water (T(2B) approximately 0-10 ms), myofibrillar water (T(21) approximately 35-50 ms), and also expelled "bulk" water (T(2) relaxation times >1000 ms). Accordingly, the present study demonstrates that definite structural changes in proteins during cooking of meat are associated with simultaneous alterations in the chemical-physical properties of the water within the meat.

Effect of surface coverage on the conformation and mobility of C18-modified silica gels

C18-modified silica gels with surface coverages of 2 to 8.2 micromol m(-2), were prepared by different synthetic pathways and characterized by Fourier Transform infrared spectroscopy (FTIR), solid-state nuclear magnetic resonance (NMR) spectroscopy, and chromatographic measurements. The effects of temperature and bonding density on the conformational order of C18-modified silica gels were studied in detail by FTIR spectroscopy. The silane functionality and degree of cross-linking of silane ligands on the silica surface were evaluated by 29Si cross-polarization magic-angle spinning (CP/MAS) NMR and the structural order and mobility of the alkyl chains were investigated by 13C CP/MAS NMR spectroscopy. CH2 symmetric and anti-symmetric stretching bands and CH2 wagging bands were used as IR probes to monitor the conformational order and flexibility of the alkyl chains in the C18 phases. Qualitative information about the conformational order was obtained from frequency shifts of the CH2 symmetric and anti-symmetric stretching bands. The relative amounts of kink/gauche-trans-gauche, double-gauche, and end-gauche conformers in the alkyl chains were determined by analysis of CH2 wagging bands. These results indicate that surface coverage plays a dominant role in the conformational order of C18-modified silica gels. The FTIR and NMR data are discussed in the context of the chromatographic shape-selectivity differences.

Surface characterisation of the evolving nature of radio frequency (RF) magnetron sputter deposited calcium phosphate thin films after exposure to physiological solution

The initial behaviour and ultimately the long-term performance of calcium phosphate (Ca–P) coatings for hard tissue implant applications are influenced by their dissolution properties. For this study, Ca–P coatings were deposited onto Ti-6Al-4V substrates using RF magnetron sputtering. The physico-chemical nature of these deposited layers was then determined both before and after annealing at 400 °C using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Furthermore, their dissolution behaviour in phosphate buffered saline (PBS) solution was also examined using similar techniques. The data shows clearly that the as-deposited coatings are amorphous when compared with the more crystalline coatings produced after annealing at 400 °C. These as-deposited coatings completely dissolve after exposure to the PBS for only 24 h; however, the dissolution rate of the annealed coatings is more restrained. Whereas the XPS and FTIR data show no change in the chemical nature of the annealed coatings after 30 days, the AFM results reveal subtle changes in the surface topography of the coatings after only 1 h of immersion. These data clearly show the utility of surface analytical techniques, such as AFM in combination with more established techniques for examining the surface properties of Ca–P coatings. Furthermore, the study also shows that calcium phosphate coatings deposited at low power using RF magnetron sputtering can undergo a decreased dissolution rate under physiological conditions they when subjected to post deposition annealing.

Complexes of fulvic acid on the surface of hematite, goethite, and akaganeite: FTIR observation

The present work extended our knowledge on the binding and complexation of a fulvic acid (FA) derived from leonardite and the iron oxides (hematite, goethite and akaganeite) by Fourier transform infrared spectroscopy (FTIR). As a prerequisite, the iron oxides were firstly prepared and characterized by transmission electron micrograph (TEM). All iron phases were single and well-described crystalloid. The FTIR data obtained by two different sampling preparation methods gave the consisting evidences that under our experimental conditions the interaction mechanism was to the ligand-exchange involving carboxylic functional groups of the FA and the surfaces sites of both hematite and goethite, while no complexation can be evidenced in the case of akaganeite, only surface adsorption. In general, the binding affinities of the iron oxides with the FA was in the order of hematite > goethite > akaganeite. The present method, although associated with some uncertainties, provided an opportunity to increase the knowledge in the field of the humic chemistry.

Effects of crystalline quality on the phase stability of cubic boron nitride thin films under medium-energy ion irradiation

To investigate the effect of radiation damage on the stability and the compressive stress of cubic boron nitride (c-BN) thin films, c-BN films with various crystalline qualities prepared by dual beam ion assisted deposition were irradiated at room temperature with 300 keV Ar+ ions over a large fluence range up to 2×1016 cm−2. Fourier transform infrared spectroscopy (FTIR) data were taken before and after each irradiation step. The results show that the c-BN films with high crystallinity are significantly more resistant against medium-energy bombardment than those of lower crystalline quality. However, even for pure c-BN films without any sp2-bonded BN, there is a mechanism present, which causes the transformation from pure c-BN to h-BN or to an amorphous BN phase. Additional high resolution transmission electron microscopy (HRTEM) results support the conclusion from the FTIR data. For c-BN films with thickness smaller than the projected range of the bombarding Ar ions, complete stress relaxation was found for ion fluences approaching 4×1015 cm−2. This relaxation is accompanied, however, by a significant increase of the width of c-BN FTIR TO-line. This observation points to a build-up of disorder and/or a decreasing average grain size due to the bombardment.

ARCHAEOLOGICAL AMBERS FROM NORTHERN ITALY: AN FTIR–DRIFT STUDY OF PROVENANCE BY COMPARISON WITH THE GEOLOGICAL AMBER DATABASE*

European geological ambers of five different localities and types, and Italian geological ambers from seven different deposits have been studied with Fourier transform infrared spectroscopy (FTIR) and diffuse‐reflectance infrared Fourier transform (DRIFT). Ambers from several localities have been characterized for the first time. The research aims to create a database of European ambers, containing both FTIR and DRIFT data. The FTIR spectra are easily comparable with the data commonly available in the literature, whereas DRIFT analyses are shown to be more useful to characterize the archaeological finds. The provenance of several archaeological ambers from northern and southern Italy, dating from the Middle Bronze Age to the Iron Age, is assessed on the basis of the developed database. Of the 35 analysed archaeological objects, all but five are composed of Baltic succinite amber.

Initial Stage Hydrogen Movement and IR Absorption Proportionality Constants In Hot-Wire Deposited SiN1.2:H During High-Temperature Annealing

AbstractSilicon nitride (SiNx:H) layers were deposited using a high deposition rate Hot-Wire CVD technique (up to 5 nm/s) and their application as passivating antireflection coating on multicrystalline silicon solar cells was investigated. An important aspect is the hydrogen release and diffusion during a short annealing treatment at temperatures well above the deposition temperature. Such annealing treatments (firing) are used during contact formation of multicrystalline solar cells.A series of SiNx:H layers with Si/N ratio in the range of 0.7-1.45 was first characterized using optical R/T measurements, Fourier Transformed Infrared Spectroscopy (FTIR) and Elastic Recoil Detection (ERD) to determine optical constants n and k, Si-H, N-H and Si-N bond densities, Si-H peak position and H content. To get more insight in the passivation process during firing, which takes place at roughly 800 °C, samples with a N/Si ratio of 1.2 were annealed at this temperature for different times (15 s – 10 min). The total bonded H content, measured with FTIR, using conventional proportionality constants as proposed by Lanford and Rand [1], seems to show an increase within the first 60 s. At longer annealing times, the bonded H content decreases, as expected. The behavior of the H content under annealing measured by FTIR and ERD can be explained by using different matrix elements for calculating the H content from the FTIR data. The matrix element for the N-H stretching mode (3343 cm-1) was determined to be (4.7±0.2)x1020 cm-2 while the Si-H stretching (2193 cm-1) was found to be (0.55±0.04)x1020 cm-2. Such high matrix elements for the N-H stretching mode have not been reported earlier. The value of the Si-H stretching mode matrix element is within the reported values for different back bonding scenarios, but low for a peak position of 2193 cm-1. The ratio between the matrix elements of 8.5 differs strongly from the ratio of 2 observed by Lanford [1] or Bohne [2].

Formation and Characterization of Inclusion Complexes of Poly(butylene succinate) with α‐ and γ‐Cyclodextrins

The inclusion complexes (ICs) of alpha- and gamma-cyclodextrins (CDs) with high-molecular-weight poly(butylene succinate) (PBS) were prepared and characterized by differential scanning calorimetry, Fourier-transform infrared spectroscopy (FT-IR), wide-angle X-ray diffraction, solid-state 13C nuclear magnetic resonance (NMR) spectroscopy, and solution 1H NMR spectroscopy. The resultant ICs were found to have channel structures. FT-IR data suggested that the ICs were stabilized by hydrogen bonds between the host CD molecules and the guest PBS chains. Through the formation of ICs, the PBS chain possibly adopts the kink conformation in the included state, as indicated by NMR analysis.

Complexes of Fulvic Acid on Hematite Interfaces: Characterization and Photochemical Properties

Fourier transform infrared spectroscopy (FTIR), combined with ultraviolet-visible spectroscopy (UV-Vis) and transmission electron micrograph (TEM), has been used to observe the interaction between fulvic acid (FA) and hematite. The FTIR data have shown that the interaction mechanism corresponds mainly to the ligand-exchange involving carboxylic functional groups of the FA and hematite surface sites. The general trends included an increase in the content of Fe(III)-humate complexes on hematite surfaces accompanied by a decrease in pH and an increasing in the ionic strength. Both UV-Vis spectroscopy and TEM images have shown that hematite can interplay with FA under acidic conditions. In particular, the TEM images have shown that the presence of FA can significantly alter the characteristics of the hematite surfaces. Photochemical experiments have shown that hematite promotes the phototransformation of lindane (γ-HCH), whereas the presence of FA adversely affects the phototransformation of the target pollutant. The hematite coated with FA displayed a somewhat better catalyzing capability compared to the hematite only.

Morphology and deformation behavior of polymer blends made of poly(styrene- co-styrenesulfonic acid) and poly(methyl methacrylate- co-4-vinylpyridine)

The effect of a small amount of ionic groups (interactions) on the morphology and deformation behavior of stoichiometric blends made of poly(styrene- co-styrenesulfonic acid) (SPS) and poly(methyl methacrylate- co-4-vinylpyridine) (MVP) was investigated by Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). FTIR data revealed that intermolecular ion–ion interactions were formed between SPS and MVP polymers, arising from proton transfer from sulfonic acid groups to pyridine groups upon blending. TEM observations show that the morphology of the blends changes from macroscopic phase separation to microscopic phase separation, and to miscibility, with increasing ion content of the blends from 0 to 6 mol%. Correspondingly, deformation behavior of the blends changes from crazing only, to curved and branched crazing, and to crazing plus shear deformation. Such changes in deformation mode can be understood as arising from the morphological changes and the increase of ‘effective’ strand density due to the formation of ionic cross-links in the blends.

Improvement of the biocompatibility of chitosan dermal scaffold by rigorous dry heat treatment

We have developed a rigorous heat treatment method to improve the biocompatibility of chitosan as a tissue-engineered scaffold. The chitosan scaffold was prepared by the controlled freezing and lyophilizing method using dilute acetic acid and then it was heat-treated at 110°Cin vacuo for 1∼3 days. To explore changes in the physicochemical properties of the heat-treated scaffold, we analyzed the degree of deacetylation by colloid titration with poly(vinyl potassium sulfate) and the structural changes were analyzed by scanning electron microscopy, Fourier transform infrared (FT-IR) spectroscopy, wide-angle X-ray diffractometry (WAXD), and lysozyme susceptibility. The degree of deacetylation of chitosan scaffolds decreased significantly from 85 to 30% as the heat treatment time increased. FT-IR spectroscopic and WAXD data indicated the formation of amide bonds between the amino groups of chitosan and acetic acids carbonyl group, and of interchain hydrogen bonding between the carbonyl groups in the C-6 residues of chitosan and theN-acetyl groups. Our rigorous heat treatment method causes the scaffold to become more susceptible to lysozyme treatment. We performed further examinations of the changes in the biocompatibility of the chitosan scaffold after rigorous heat treatment by measuring the initial cell binding capacity and cell growth rate. Human dermal fibroblasts (HDFs) adhere and spread more effectively to the heat-treated chitosan than to the untreated sample. When the cell growth of the HDFs on the film or the scaffold was analyzed by an MTT assay, we found that rigorous heat treatment stimulated cell growth by 1.5∼1.95-fold relative to that of the untreated chitosan. We conclude that the rigorous dry heat treatment process increases the biocompatibility of the chitosan scaffold by decreasing the degree of deacetylation and by increasing cell attachment and growth.

Taxonomic discrimination of flowering plants by multivariate analysis of Fourier transform infrared spectroscopy data.

Fourier transform infrared spectroscopy (FTIR) provides biochemical profiles containing overlapping signals from a majority of the compounds that are present when whole cells are analyzed. Leaf samples of seven higher plant species and varieties were subjected to FTIR to determine whether plants can be discriminated phylogenetically on the basis of biochemical profiles. A hierarchical dendrogram based on principal component analysis (PCA) of FTIR data showed relationships between plants that were in agreement with known plant taxonomy. Genetic programming (GP) analysis determined the top three to five biomarkers from FTIR data that discriminated plants at each hierarchical level of the dendrogram. Most biomarkers determined by GP analysis at each hierarchical level were specific to the carbohydrate fingerprint region (1,200-800 cm(-1)) of the FTIR spectrum. Our results indicate that differences in cell-wall composition and structure can provide the basis for chemotaxonomy of flowering plants.

Study of SEI Layer Formed on Graphite Anodes in PC/LiBOB Electrolyte Using IR Spectroscopy

Formation of the SEI layer on graphite anodes cycled in propylene carbonate (PC) lithium bis(oxolato)borate (LiBOB) electrolyte was studied by ex-situ Fourier Transform Infrared Spectroscopy (FTIR) analysis in the attenuated total reflection (ATR) mode. The results provide a more refined description of the composition than earlier analyses with x-ray photoelectron spectroscopy (XPS). The vibrational spectra clearly show that electrochemical reduction of the BOB anion is a part of the SEI formation chemistry. Carboxylate and/or oxalate functional groups derived from the BOB anion were the components assigned as the ''semicarbonate'' species in the C 1s XPS spectra of the SEI layer formed in LiBOB electrolyte. Reduction of the BOB anion changes the oxygen coordination around the B atom from tetrahedral BO4 to trigonal BO3, e.g., meta- or orthoborate. Based on the combination of electrochemical and FTIR data, we propose that the preferential reduction of the BOB anion versus the PC solvent molecule is responsible for the cyclability of graphite anodes in purely PC-based electrolyte.

Selection of calibration set samples in determination of olive oil acidity by partial least squares–attenuated total reflectance–Fourier transform infrared spectroscopy

A chemometric method has been applied for the determination of the free fatty acid (FFA) concentration in commercial olive oil samples of different types an origins by using Fourier transform infrared spectroscopy (FTIR) attenuated total reflectance (ATR) measurements. Different methods for selecting the training set, including hierarchical cluster analysis, were applied and compared. The prediction capabilities of partial least squares (PLS) multivariate calibration methods, net analyte signal (NAS) preprocessing followed by PLS or classical least squares (CLS) regression method of ATR–FTIR data were evaluated. Several aspects, like spectral range to be considered, different preprocessing alternatives (mean centering, multiplicative scattering correction, standard normal variate (SNV)), together with a critical evaluation of the calibration set were made on using the mean square error of cross-validation and prediction, as control parameters. Using a calibration set of 16 samples the properties of 28 samples were predicted with relative precision of triplicates of 0.017 wt.%. The mean difference between predicted and actual values and the standard deviation of mean differences were −0.001 and 0.037 wt.%, respectively. The limit of detection (LOD), sensitivity and selectivity of the methodology developed were evaluated in terms of the net analyte signal, being found a limit of detection of 0.072 wt.%, a sensitivity value of 0.077 in terms of analytical signal per unit of concentration, being expressed that in wt.%, and a linear relationship ( R 2=0.9963) between selectivity and FFA concentration (equivalent to 0.24% for a sample containing 1 wt.% of FFA).

Use of Fourier-transform infrared spectroscopy for typing of Candida albicans strains isolated in intensive care units.

Comparative studies of Candida albicans strains are essential for proving cross-infections in epidemiological investigations. Typing of C. albicans strains is mainly based on genotypic methods. Fourier-transform infrared (FTIR) spectroscopy is described in this study as a novel phenotypic approach to the typing of C. albicans. The first step in the approach was the standardization of sample preparation (culture conditions and sampling parameters) and acquisition and classification parameters (spectral acquisition, spectral window selection, classification algorithm, and heterogeneity threshold). The second step consisted of validating the established parameters with a set of 79 strains of C. albicans isolated over 4 months from nine patients hospitalized in two intensive care units. Strains were isolated from multiple anatomical sites with repeated sampling. FTIR spectroscopy results were compared to randomly amplified polymorphic DNA (RAPD) results; this analysis showed that the amplification patterns of strains isolated from a given patient were identical and that different patients had different profiles. FTIR spectroscopy data were analyzed by hierarchical clustering performed with the second-derivative spectra. This classification revealed nine groups, one per patient. Only one spectrum out of 79 was misclassified by the FTIR spectroscopy method. RAPD and FTIR spectroscopy results were in good agreement, showing that, when nosocomial candidiasis transmission is suspected and urgent information is needed, this technique may be useful as a quick identification tool to give solid clues before confirmation by a genotypic method.

Formation of Physically Stable Amorphous Drugs by Milling with Neusilin

Each of four drugs (ketoprofen, indomethacin, naproxen, and progesterone) was milled with Neusilin (amorphous magnesium aluminosilicate) to effect conversion from crystalline to amorphous states, and the physical stability of the resultant drugs was investigated. Ball milling the drugs alone for 48h resulted in no amorphization. X‐ray powder diffractometry (XPD), birefringence, and differential scanning calorimetry (DSC) data indicated amorphization of all the four drugs on ball milling with Neusilin. Fourier transform infrared spectroscopy (FTIR) data showed a reduction in the absorbance of the free and the hydrogen‐bonded acid carbonyl peaks accompanied by a corresponding increase in the absorbance of the carboxylate peak, indicating an acid–base reaction between the carboxylic acid‐containing drugs and Neusilin on milling. On storage of milled powders (at 40°C and 75% RH for 4 weeks), XPD, birefringence, and DSC data showed the absence of reversion to the crystalline state, and FTIR data revealed continued absence of the carbonyl peaks. Whereas the carboxylic acid‐containing drugs convert from their crystalline acid form to amorphous salt form on milling with Neusilin, progesterone seems to interact with Neusilin via hydrogen bonding. The amorphous Neusilin‐bound states of all four drugs were physically stable during storage. The water of adsorption seems to mediate the conversion of the crystalline state to an amorphous Neusilin‐bound state.

Synthesis and Aggregation of Benzyl(2-acylaminoethyl)dimethylammonium Chloride Surfactants

The following scheme has been employed to synthesize the title cationic surfactants: RCO2H (+NH2CH2CH2N(CH3)2, toluene) → RCONHCH2CH2N(CH3)2 (1a−1d) (+PhCH2Cl, CH3CN) → RCONHCH2CH2N+(CH3)2CH2C6H5Cl- (2a−2d). RCO2H refers to decanoic, dodecanoic, tetradecanoic, and hexadecanoic acid, respectively. Aggregation of these surfactants in water has been studied at 25 °C by measuring solution conductivity, surface tension, and electromotive force and by using Fourier transform infrared spectroscopy (FTIR). Increasing the length of R resulted in an increase of the aggregation number and a decrease in minimum area/surfactant at the solution/air interface, critical micelle concentration, and degree of counterion dissociation. Gibbs free energies of adsorption at the solution/air interface and of micelle formation were calculated and compared to those of other cationic surfactants. Contributions to these free energies from methylene groups of the hydrophobic tail and surfactant headgroup were calculated. The former are similar to those of other cationic surfactants, whereas the latter are smaller, i.e., more negative. That is, transfer of the headgroup from bulk water to the interface and/or to the micelle is more favorable. This is attributed to intermolecular H-bonding of monomers at the solution/air interface and/or in the aggregate, via the amide group, in agreement with our FTIR data.