Main Chain Axis Research Articles

Reappraising the seismogenic potential of a low-strain rate region: Active faulting in the eastern Siena Basin (southern Tuscany, Italy)

We investigated the active tectonics and earthquake potential of the eastern Siena Basin, a slowly deforming portion of southern Tuscany in the inner Northern Apennines. This region hosts several historical settlements and valuable cultural heritage, but also frequent background seismicity and rare damaging earthquakes in the Mw range 5.0–6.2. We describe in detail an active, capable, and seismogenic fault system that we identified in the eastern Siena Basin, a few kilometers south-east of the city of Siena, thanks to the presence of an active quarry (Cava Capanni) that exploits travertines of Middle Pleistocene-Holocene age. Travertines are unique rock masses that may preserve living evidence of active and seismogenic faulting, thus providing remarkable seismotectonic insight. The active fault system consists of at least two segments rupturing travertines younger than 45 ka, with a cumulative vertical displacement of 111 cm, and an estimated minimum slip rate of 0.02–0.03 mm/y. We maintain that this displacement is the result of at least three coseismic movements accompanied by clastic dykes injected within the fault damage zone due to liquefaction phenomena. The fault system is seen to extend east of the quarry, affecting Pliocene and Mesozoic deposits.The Cava Capanni fault system is evidence of a poorly understood but potentially seismogenic tectonic mechanism of regional extent. Its orientation and kinematics are compatible with the activity of faults that are oriented obliquely or orthogonally to the main chain axis, in contrast with the setting of the axial and outer zone of the Northern Apennines, where extension and compression are accommodated by Apennines-parallel faults.

Phylogenetics and biomineralization of a novel magnetotactic Gammaproteobacterium from a freshwater lake in Beijing, China.

Magnetotactic bacteria (MTB) have the remarkable capability of producing intracellularly membrane-enveloped magnetic nanocrystals (i.e. magnetosomes) and swimming along geomagnetic field lines. Despite more than 50 years of research, bacterial diversity and magnetosome biomineralization within MTB are relatively less known in the Gammaproteobacteria class than other groups. This is incompatible with the status of Gammaproteobacteria as the most diverse class of gram-negative bacteria with a number of ecologically important bacteria. Here, we identify a novel MTB strain YYHR-1 affiliated with the Gammaproteobacteria class of the Pseudomonadota phylum from a freshwater lake. In YYHR-1, most magnetosome crystals are organized into a long chain aligned along the cell long axis; unusually, a few small superparamagnetic crystals are located at the side of the chain, off the main chain axis. Micromagnetic simulations indicate that magnetostatic interactions among adjacent crystals within a chain reduce the Gibbs energy to enhance chain stability. Genomic analysis suggests that duplication of magnetosome gene clusters may result in off-chain magnetosomes formation. By integrating available genomic data from Gammaproteobacteria, the phylogenetic position of MTB in this class is reassigned here. Our new findings expand knowledge about MTB diversity and magnetosome biomineralization, and deepen understanding of the phylogenetics of the Gammaproteobacteria.

Assessing the control factors upon glacial valley development in southernmost Patagonia (Fuegian Andes of Argentina)

Research on landscape glacial modelling provides particularly relevant information about the complex connection between climate change and relief evolution. Glacial valleys – the most distinctive landforms in alpine-type settings – were systematically mapped across the Fuegian Andes of Argentina, southernmost Patagonia, and quantitatively investigated in terms of the geoenvironmental agents that controlled their formation. A total of 646 troughs were identified and studied in four sub-areas with contrasting past glacial cover. Our observations demonstrate that longer valleys are also the deeper, less steep (in long profile), more sinuous and lower, and that maximum elevation was the main control of altitudinal range, mean and maximum slope, and minimum depth. Overall, it is considered that valley development was subject to conditioning by pre-glacial topography, geological structure and climatic forcings. Specifically, valley's spatial arrangement indicates that glaciers responsible for their erosion (possibly during the early Pleistocene) adjusted to a fluvial drainage network organized according to a marked structural control, mainly associated with Magallanes-Fagnano and Canal Beagle regional strike-slip systems. The predominance and higher degree of development of southern slope valleys reveal that north-south differential insolation effect was determinant in the Fuegian glaciers' balance during extensive time-lapses in glacial cycles, likely reflecting a scenario of relative aridity and comparatively clear skies. Morning-afternoon contrasts in solar radiation receipt and, specially, humid winds from the west (regional westerlies) would have also produced a moderate eastward bias in valley direction. In the western and central sectors, formerly covered by the Cordillera Darwin Icefield, the surface of Fagnano and Beagle outlet palaeolobes and other major collectors constituted a comparatively high base level for mountain glaciers' incision during full glacial conditions, leading to the creation of profuse, short hanging valleys. In the eastern domain, on the contrary, glaciers appear to have been essentially regulated by the topoclimatic factors, attaining greater dimensions and flowing down to lower altitudes in south- and southeast-facing slopes. Finally, in marginal, lower mountains (away from the main chain axis) ice is thought to have formed only under the most severe glacial episodes in the zone.

Advanced surface FTIR spectroscopy analysis of poly(ethylene)-block-poly(ethylene oxide) thin film adsorbed on gold substrate

This study investigates the thin film adsorption on gold substrate of PE-b-PEO block copolymer. The originality is to use Polarization Modulation – InfraRed Reflection Absorption Spectroscopy (PM-IRRAS) to probe the copolymer thin film conformational state when physisorbed. The PM-IRRAS technology allows to measure surface-specific FTIR spectra of thin films due to differential reflectivity of p- and s-polarized light from interfaces. The anisotropy and the exaltation of the electric field created at the copolymer/metal interface are exploited to infer macromolecular adsorption and conformational changes induced by the adsorption. In addition to spectroscopic analyzes, the surface topology of the thin film of copolymer and the ability of the blocks to crystallize at the solid interface were investigated by Atomic Force Microscopy (AFM). Vibrational modes analysis of the PM-IRRAS spectra unambiguously show first that the PEO sequences of the PE-b-PEO copolymer are adsorbed preferentially on the Au substrate in flatten conformations relative to the substrate surface with an orientation angle of 27° between the main chain axis and the gold substrate and second that the PE sequences of PE blocks are randomly oriented compared to the gold surface and rejected as an amorphous phase to the upper surface of the copolymer film.

High flexible ether-free semi-crystalline fuel cell membranes: Molecular-level design, assembly structure and properties

The development of polymer exchange membranes (PEMs) with high proton conductivity under high temperature and low relative humidity (RH) conditions is important to the improvement of the comprehensive performance of the fuel cell. In this paper, we present a novel approach for the design of semi-crystalline fluorinated PEMs (FSPP-1) via Ni(0)-catalyzed coupling polymerization. The structural characteristics of FSPP-1 are composed of retaining a portion of the fluorinated matrix (coil units) and introducing aromatic π-π interactions in the hydrophilic block (rod units), as well as precisely controlling the same block length along the main chain axis, which is a similar, molecular-level approach as the prototypical Nafion™ 117. The morphology, water state, and proton conductivity of FSPP-1 were investigated in detail, and the results show higher proton conductivity at 40% RH at 80 °C. The study also revealed that a dense, narrow distribution of hydrophilic nanochannels were formed with good connectivity of the hydrophilic nanochannels in FSPP-1. More importantly, π-π interactions in the hydrophilic block and helical perfluoroalkyl chains in the hydrophobic block coexisted in FSPP-1 ionomers, forming more small and dense crystallite domains, which was found to be beneficial to improving the stability of the nanochannels at elevated temperature and low RH. This strategy to simultaneously increase the density of ion transport channels and high temperature stability provides a baseline for the molecular-level design of high temperature PEMs.

Synthesis and Structural Analysis of Aspergillus fumigatus Galactosaminogalactans Featuring α‐Galactose, α‐Galactosamine and α‐N‐Acetyl Galactosamine Linkages

AbstractGalactosaminogalactan (GAG) is a prominent cell wall component of the opportunistic fungal pathogen Aspergillus fumigatus. GAG is a heteropolysaccharide composed of α‐1,4‐linked galactose, galactosamine and N‐acetylgalactosamine residues. To enable biochemical studies, a library of GAG‐fragments was constructed featuring specimens containing α‐galactose‐, α‐galactosamine and α‐N‐acetyl galactosamine linkages. Key features of the synthetic strategy include the use of di‐tert‐butylsilylidene directed α‐galactosylation methodology and regioselective benzoylation reactions using benzoyl‐hydroxybenzotriazole (Bz‐OBt). Structural analysis of the Gal, GalN and GalNAc oligomers by a combination of NMR and MD approaches revealed that the oligomers adopt an elongated, almost straight, structure, stabilized by inter‐residue H‐bonds, one of which is a non‐conventional C−H⋅⋅⋅O hydrogen bond between H5 of the residue (i+1) and O3 of the residue (i). The structures position the C‐2 substituents almost perpendicular to the oligosaccharide main chain axis, pointing to the bulk solvent and available for interactions with antibodies or other binding partners.

Synthesis and Structural Analysis of Aspergillus fumigatus Galactosaminogalactans Featuring α-Galactose, α-Galactosamine and α-N-Acetyl Galactosamine Linkages.

Galactosaminogalactan (GAG) is a prominent cell wall component of the opportunistic fungal pathogen Aspergillus fumigatus. GAG is a heteropolysaccharide composed of α-1,4-linked galactose, galactosamine and N-acetylgalactosamine residues. To enable biochemical studies, a library of GAG-fragments was constructed featuring specimens containing α-galactose-, α-galactosamine and α-N-acetyl galactosamine linkages. Key features of the synthetic strategy include the use of di-tert-butylsilylidene directed α-galactosylation methodology and regioselective benzoylation reactions using benzoyl-hydroxybenzotriazole (Bz-OBt). Structural analysis of the Gal, GalN and GalNAc oligomers by a combination of NMR and MD approaches revealed that the oligomers adopt an elongated, almost straight, structure, stabilized by inter-residue H-bonds, one of which is a non-conventional C-H⋅⋅⋅O hydrogen bond between H5 of the residue (i+1) and O3 of the residue (i). The structures position the C-2 substituents almost perpendicular to the oligosaccharide main chain axis, pointing to the bulk solvent and available for interactions with antibodies or other binding partners.

Effect of molecular weight on microcrystalline structure formation in polymer with perylenediimide side chain

The effect of molecular weight on the molecular aggregation structure of polymers bearing a pendant perylenediimide (PDI) side chain, designated PAc12PDI, was investigated using synchrotron radiation X-ray diffraction measurements. It was found that depending on molecular weight, either the main chain axis or the side chain axis behaves as the longitudinal axis in fiber samples and was aligned parallel to the fiber axis. A similar phenomenon is present in thin film samples, but was complicated by the additional influence of the interfacial free energy of the side chain group. Even in the case of the polymer with lower molecular weight, the face plane of PDI was found to show both parallel and perpendicular orientations to the substrate (i.e., flat-on and edge-on orientations). On the other hand, if the length of the main chain is sufficiently long with respect to the length of the side chain, the face plane of PDI was oriented perpendicular to the substrate, leading to an edge-on orientation in the thin film. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 2275–2283

Thermotropic Behavior of Syndiotactic Polymethylenes with ω-[4-(trans-4-Pentylcyclohexyl)phenoxy]alkyloxycarbonyl Side Chains

A series of syndiotatic P5CPn polymethylenes was prepared with 4-(trans-4-pentylcyclohexyl)phenoxy moieties linked to each backbone carbon atom via an alkyloxycarbonyl spacer and with even numbers of alkyl carbons n ranging from 2 to 14, and their thermotropic behaviors were investigated. The P5CPn, except P5CP2, formed smectic phases in which the rod-like polymethylene backbones were arranged in rectangular lattices, and the side-chain mesogens were aggregated into layers parallel to the shorter sides of the rectangular lattices. The packing of the mesogens changed with decreasing temperature from smectic C-like to smectic I-like (SmI-like) for n = 4–8 and from smectic A-like to SmI-like for n = 10–14. In the SmI-like phases, each mesogen along the main-chain axis was connected to every sixth backbone carbon atom, revealing a correlation between the packing of the mesogens and the main-chain conformation of a 3/2 helix. Conversely, P5CP2 formed a smectic phase with the main chains arranged in rows and with the mesogens barely aggregated into layers due to the short spacers.

アコーディオン伸縮振動するπ共役系らせん高分子の合成とらせんピッチの制御

Poly(alkyl propiolate)s (PAP), e.g., Poly(n-heptyl propiolate) (PnHepP) and Poly((s)-2-octyl propiolate) (Ps2OctP) having an achiral or a chiral ester side chain were stereoregularly prepared with a Rh complex catalyst, [Rh(nbd)Cl]2 (nbd=norbornadiene), at 40 °C in methanol, respectively. The temperature dependence 1H and 13C NMR spectra of PAPs and their spectral simulations indicated that the restricted rotation around the ester O-C bond takes place through the so-called 3-site jump conformation. The spectra also exhibited that the helical conjugated main-chain of Ps2OctP was largely oscillating between the sequences of contracted helix and stretched helix in the time scale of the NMRs, although the degree of the oscilation of PnHepP was fairly small compared to that of Ps2OctP. The UV-vis and IR spectra of them supported that PAPs have at least two helical conformations, i.e., contracted and stretched helices. Therefore, these spectra supported the oscillation of the helix along the main-chain axis. The proposed model calculated by MMFF94 also indicated the accordion-like helix oscillation of contracted and stretched helices (HELIOS) of PAPs which was synchronized with restricted 3-site jump rotation around the ester O-C bond in the side-chain.

Accordion-like Oscillation of Contracted and Stretched Helices of Polyacetylenes Synchronized with the Restricted Rotation of Side Chains

A chiral substituted acetylene, (s)-2-octyl propiolate, was stereoregularly polymerized using a catalyst, [Rh(nbd)Cl]2, at 40 °C in methanol to give the corresponding helical polymer, Ps2OcP. The changes of (1)H and (13)C NMR spectra in line shapes and splitting patterns were consistently interpreted in terms of restricted rotation around the ester O-*C bond, ~O-*C(ε)H(ε)(R)~, R = a branched CH(ε)3 in the ester side chains rather than the helix inversion with the aid of a 3-site jump model. Three peaks due to the branched methyl H(ε) proton and its C(η) carbon observed at 0 °C suggested the formation of three rotamers called A, B, and C, based on the presence of the contracted helix and stretched helix forms that have an intrinsic helical pitch. Furthermore, an accordion-like helix oscillation (HELIOS) along the main chain axis was proposed to explain the temperature dependence spectral changes observed in (1)H and (13)C NMR, UV-vis, and circular dicromism (CD) spectra. The temperature dependence UV-vis and CD spectra of Ps2OcP corroborate the presence of contracted and stretched one-handed helix sense polymers in solution in which the helical pitches and their persistence lengths depend on the temperature.

Accordion-like oscillation of contracted and stretched helices of polyacetylenes synchronized with the restricted rotation of side chains.

A chiral substituted acetylene, (s)-2-octyl propiolate, was stereoregularly polymerized using a catalyst, [Rh(nbd)Cl]2, at 40 °C in methanol to give the corresponding helical polymer, Ps2OcP. The changes of 1H and 13C NMR spectra in line shapes and splitting patterns were consistently interpreted in terms of restricted rotation around the ester O–*C bond, ∼O–*CeHe(R)∼, R = a branched CHe3 in the ester side chains rather than the helix inversion with the aid of a 3-site jump model. Three peaks due to the branched methyl He proton and its Cη carbon observed at 0 °C suggested the formation of three rotamers called A, B, and C, based on the presence of the contracted helix and stretched helix forms that have an intrinsic helical pitch. Furthermore, an accordion-like helix oscillation (HELIOS) along the main chain axis was proposed to explain the temperature dependence spectral changes observed in 1H and 13C NMR, UV–vis, and circular dicromism (CD) spectra. The temperature dependence UV–vis and CD spectra of P...

Helix oscillation of polyacetylene esters detected by dynamic 1H NMR, IR, and UV-vis methods in solution

An aliphatic substituted acetylene, n-heptyl propiolate, was stereoregularly polymerised using a catalyst, [Rh(nbd)Cl]2, at 40 °C in methanol to obtain the corresponding helical polymer, PnHepP. The changes in the line shapes and splitting patterns of the 1H NMR spectra were interpreted consistently as representing restricted rotation around the ester O–Ce bond in –O–CeHe2(R)– (R = n-hexyl alkyl chains), rather than helix inversion, with the aid of a 3-site jump model. A two-line peak corresponding to the ester methylene protons of –O–CH2– observed at 30 °C suggested the formation of three rotamers designated as A, B, and C based on the presence of contracted helix and stretched helix forms, each of which has an intrinsic helical pitch with a helical cis–cisoid structure. Furthermore, an accordion-like helix oscillation (HELIOS) along the main chain axis was proposed to explain the temperature dependence of spectral changes observed in the 1H NMR, UV-vis, and IR spectra. The temperature dependence of the UV-vis and 1H NMR spectra of PnHepP corroborated the presence of contracted and stretched one-handed helix sense polymers in solution.

Role of Packing Defects in the Evolution of Allostery and Induced Fit in Human UDP-Glucose Dehydrogenase

Allosteric feedback inhibition is the mechanism by which metabolic end products regulate their own biosynthesis by binding to an upstream enzyme. Despite its importance in controlling metabolism, there are relatively few allosteric mechanisms understood in detail. This is because allostery does not have an identifiable structural motif, making the discovery of new allosteric enzymes a difficult process. The lack of a conserved motif implies that the evolution of each allosteric mechanism is unique. Here we describe an atypical allosteric mechanism in human UDP-α-d-glucose 6-dehydrogenase (hUGDH) based on an easily acquired and identifiable structural attribute: packing defects in the protein core. In contrast to classic allostery, the active and allosteric sites in hUGDH are present as a single, bifunctional site. Using two new crystal structures, we show that binding of the feedback inhibitor, UDP-α-d-xylose, elicits a distinct induced-fit response; a buried loop translates ∼4 Å along and rotates ∼180° about the main chain axis, requiring surrounding side chains to repack. This allosteric transition is facilitated by packing defects, which negate the steric conformational restraints normally imposed by the protein core. Sedimentation velocity studies show that this repacking favors the formation of an inactive hexameric complex with unusual symmetry. We present evidence that hUGDH and the unrelated enzyme dCTP deaminase have converged to very similar atypical allosteric mechanisms using the same adaptive strategy, the selection for packing defects. Thus, the selection for packing defects is a robust mechanism for the evolution of allostery and induced fit.

Synthesis and Mesomorphic Properties of Main-Chain Polymers Containing V-Shaped Bent-Core Mesogens with Acute-Subtended Angle

Four achiral polymers with V-shaped bent-core mesogens in the main chain have been synthesized by polycondensation, and the effect of acute-angled central cores (Ar= 1,2-phenylene or 2,3-naphthylene) and lateral halogen substituents (X = F or Cl) was studied. All polymers were only soluble in strong acids such as H 2 SO 4 and CF 3 CO 2 H. The solution viscosities were in the range of 0.31―0.81 dL/g. Although polymers contained a V-shaped bent-core mesogen with acute-angled configuration in their main chain, in general they were semicrystalline in the solid state and could form smectic C phases in the melt state. However, polymer with Ar/X 1,2-phenylene/Cl was almost amorphous. Especially, polymer with Ar/X = 2,3-naphthylene/F formed a ferroelectric smectic C phase (SmCP F ), possibly B7 phase: on ground state the spontaneous polarization was not zero (P s = 140 nC cm ―2 ), and on applying an triangular electric field a switching occurred by a collective rotation of the mesogens around the main chain axis.

Poly(diphenylacetylene) Bearing Long Alkyl Side Chain via Silylene Linkage: Its Lyotropic Liquid Crystallinity and Optical Anisotropy

The liquid crystalline properties and optical anisotropy of poly(diphenylacetylene) bearing an n-octadecylsilane moiety in the side chain, poly(1-phenyl-2-p-{dimethyl-n-octadecylsilylphenyl}acetylene) (C18-PDPA), were investigated in detail. C18-PDPA exhibited unexpected smectic phase liquid crystallinity in highly concentrated aromatic organic solvents such as toluene, despite its extremely high molecular weight of 4.18 × 106 g/mol and a fairly wide polydispersity index of 2.5. This lyotropic liquid crystallinity was derived from: a high molecular stiffness (expected from the high viscosity index of α ≈ 1.03), a high degree of intermolecular packing (the fractional free volume ≈ 0.16), and ultrahigh molecular weight. The two major absorption bands, located at 430 and 370 nm, are attributed to the π−π* transition parallel to the main chain and the localized π−π* transition with a charge-transfer characteristic among mesogenic repeating units perpendicular to the main chain axis, respectively. C18-PDPA ex...

Measuring Molecular Order in Poly(3-alkylthiophene) Thin Films with Polarizing Spectroscopies

We measured the molecular order of poly(3-alkylthiophene) chains in thin films before and after melting through the combination of several polarized photon spectroscopies: infrared (IR) absorption, variable angle spectroscopic ellipsometry (SE), and near-edge X-ray absorption fine structure (NEXAFS). The data from the various techniques can be uniformly treated in the context of the dielectric constant tensor epsilon for the film. The combined spectroscopies allow determination of the orientation distribution of the main-chain axis (SE and IR), the conjugated pi system normal (NEXAFS), and the side-chain axis (IR). We find significant improvement in the backbone order of the films after recrystallization of the material at temperatures just below the melting temperature. Less aggressive thermal treatments are less effective. IR studies show that the changes in backbone structure occur without significant alteration of the structure of the alkyl side chains. The data indicate that the side chains exhibit significant disorder for all films regardless of the thermal history of the sample.

Local order in polycarbonate glasses by 13C{19F} rotational‐echo double‐resonance NMR

AbstractNearest‐neighbor chain packing in a homogeneous blend of carbonate 13C‐labeled bisphenol A polycarbonate and CF3‐labeled bisphenol A polycarbonate has been characterized using a shifted‐pulse version of magic‐angle spinning 13C{19F} rotational‐echo double‐resonance (REDOR) NMR. Complementary NMR experiments have also been performed on a polycarbonate homopolymer containing the same 13C and 19F labels. In the blend, the 13C observed spin was at high concentration, and the 19F dephasing or probe spin was at low concentration. In this situation, an analysis in terms of a distribution of isolated heteronuclear pairs of spins is valid. A comparison of the results for the blend and homopolymer defines the NMR conditions under which higher concentrations of probe labels can be used and a simple analysis of the REDOR results is still valid. The nearest neighbors of a CF3 on one chain generally include a carbonate group on an adjacent chain. A direct interpretation of the REDOR total dephasing for the polycarbonate blend indicates that at least 75% of carbonate‐carbon 13C···F3 nearest neighbors are separated by a narrow distribution of distances 4.7 ± 0.3 Å. In addition, analysis of the variations in REDOR spinning‐sideband dephasing shows that most of the 13C···F3 dipolar vectors have a preferred orientation relative to the polycarbonate mainchain axis. This combination of distance and orientational constraints is interpreted in terms of local order in the packing of the carbonate group of one polycarbonate chain relative to the isopropylidene moiety in a neighboring chain. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2760–2775, 2006

Liquid Crystalline Hydrogels: Mesomorphic Behavior of Amphiphilic Polyacrylates Bearing Cholesterol Mesogen

Copolymers composed of 5-acryloyloxypentyl cholesterate (Ch5A) and acrylic acid (AA), poly(Ch5A-co-AA)s, were prepared changing their molar ratio, and their mesomorphic behaviors were investigated. Wide- and small-angle X-ray diffraction studies showed that poly(Ch5A-co-AA)s with a Ch5A mole fraction, F, of 0.20 and larger showed the smectic A phase in which side chains are arranged perpendicularly to the main-chain axis forming bilayers. The structural ordering and the clearing temperature, Tc, increased with decreasing F. The copolymers with F of around 0.10 exhibited a mesophase showing extremely high Tc and longer periodic spacing than the SmA phase. The copolymers of F = 0.05 and higher were not dissolved in water but swelled to form hydrogels with mesomorphic properties, presumably due to the physical cross-linking of hydrophobic aggregates of Ch5A side chains. The relationship between the uncommon thermotropic behavior and the mesomorphic structure formed by the specific interaction of chiral Ch5A components was discussed.

Molecular orientation of EVA chains adsorbed on chemically controlled surfaces: influence of specific interactions

AbstractMolecular orientation of ethylene–vinyl acetate (EVA) copolymer nanofilms adsorbed on chemically controlled surfaces is studied. Four EVA copolymers with different contents of vinyl acetate (VA) were spin‐coated onto gold, COOH and NH2 functionalized substrates in order to study chain behaviour when adsorbed in a quasi‐two‐dimensional system. Polarization‐modulation infrared reflection–absorption spectroscopy (PM‐IRRAS), a very suitable technique to study thin films, was the key to quantitative calculation of EVA chain orientational angles. Acid–base interactions between carbonyl groups of the chain ramification (vinyl acetate units) and the surface functionalities are evidenced on the basis of infrared spectra. Their incidence on the molecular orientation is also discussed.Our results show a quasi‐parallel orientation of EVA main chains with respect to the surface plane for all adsorption substrates. At the same time, orientation changes of the acetate groups are observed when the EVA copolymer is adsorbed onto functionalized substrates, suggesting that acid–base interactions could influence the orientation of these groups. However, these changes are limited and cannot reorient the main chain axis. Moreover, our results show that increasing VA content in the chain does not lead to more carbonyl functions involved in acid–base interactions with the adsorption surface. This fact also will be discussed. Copyright © 2003 John Wiley & Sons, Ltd.