Sulfophthalide cycle cleavage and formation of fluorenyl structures upon poly(diphenylene sulfophthalide) thermolysis

Thermolysis of poly(diphenylene sulfophthalide) (PDSP) in the temperature range from 100 to 500 °C was studied by IR and UV-Vis spectroscopy and thermogravimetric analysis. A series of absorption bands in the IR spectrum of PDSP were assigned on the basis of the theoretical calculations of the IR spectrum of diphenyl sulfophthalide used as a model compound, in particular, ν_as(S=O) = 1352 cm^?1, ν_s(S=O) = 1196 cm^?1, ν(C-O) ～ 920 cm^?1, ν(S-O) = 824 cm^?1, and δ(SO₂) = 576 cm^?1. The sulfophthalide cycle (SPC) in PDSP decomposes at the thermolysis temperatures in a range of 260–400 °C. An analysis of the IR spectra of the thermolyzate and the quantum chemical calculations of the IR spectra of the model compounds confirmed the predominant formation of fluorenyl structures in the thermolyzed polymer. The changes in the UV-Vis spectra observed upon the thermolysis of thin films of PDSP (the hypsochromic shift of the long-wavelength absorption band from 271 to 263 nm and the appearance a shoulder at ～310 nm) and the results of TD-DFT calculations of the UV-Vis spectra of the model compounds are consistent with the hypothesis about the formation of fluorenyl structures. The general scheme of PDSP thermolysis at 260–400 °C was proposed in which the major process is the formation of fluorenyl fragments in macromolecules of the polymer due to the intramolecular ring closure in biradicals formed by the SPC cleavage.     

FTIR studies of polyimides. II. Factors affecting quantitative measurement

Measurement of imidization by IR spectroscopy has frequently been reported to give results that are either insensitive to changes in the latter part of the cure or in conflict with observations by other methods. However, an analysis of imide formation using the 1370 cm^?1 band (C? N stretch) in conjunction with the 1500 cm^?1 aromatic band as an internal standard appears capable of giving precise, internally consistent measurements for the most commonly used polyimide structures, for samples that are measured in transmission. Measurements of imide content in ultrathin films by grazing incidence reflection spectroscopy appear to be at least semiquantitative. © 1993 John Wiley & Sons, Inc.     

Infrared study of adsorption of methanol,deuterated methanol and ethylene on the surface of ZSM-5 type zeolite

The surface species resulting in exposing of the ZSM-5 zeolite at elevated temperatures to methanol, deuterated methanol or ethylene have been studied by IR method.The three-step adsorption at 150°, 300°, 420° C or one-step adsorption at 420° C have been carried out in order to prepare the samples for IR. In all cases the most prominent band appeared in the range 1495–1515 cm^?1; besides two bands at about 1470 and 1370 cm^?1 have been observed. On the basis of Greenler's results and of the shift values of the bands in our spectrum of adsorbed deuterated methanol it was supposed that the band 1495–1515 cm^?1 is due to the OCO group from the surface species. Moreover these species would involve both oxygen atoms from the surface of zeolite but not from OH groups of methanol.     

Dielectric properties of oxydianiline‐based polyimide thin films according to the water uptake

For polyimide thin films, the dielectric properties were investigated with the capacitance and optical methods. The dielectric constants of the 4,4′‐oxydianiline (ODA)‐based polyimide thin films varied from 2.49 to 3.10 and were in the following decreasing order: 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA)–ODA > 1,2,4,5‐benzenetetracarboxylic dianhydride (PMDA)–ODA > 4,4′‐hexafluoroisopropylidene diphthalic dianhydride (6FDA)–ODA. According to the absorption of water, the diffusion coefficients in the films varied from 4.8 × 10^?10 to 7.2 × 10^?10 cm²/s and were in the following increasing order: BPDA–ODA < PMDA–ODA < 6FDA–ODA. The dielectric constants and diffusion coefficients of the polyimides were affected by the morphological structures, including the molecular packing order. However, because of the water uptake, the changes in the dielectric constants in the polyimide thin films varied from 0.49 to 1.01 and were in the following increasing order: BPDA–ODA < 6FDA–ODA < PMDA–ODA. Surprisingly, 6FDA–ODA with bulky hexafluoroisopropylidene groups showed less of a change in its dielectric constant than PMDA–ODA. The total water uptake for the polyimide thin films varied from 1.43 to 3.19 wt % and was in the following increasing order: BPDA–ODA < 6FDA–ODA < PMDA–ODA. This means that the changes in the dielectric constants in the polyimide thin films were significantly related to the morphological structure and hydrophobicity of hexafluoroisopropylidene groups. Therefore, the morphological structure and chemical affinity in the polyimide thin films were important factors in controlling the dielectric properties. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2190–2198, 2002     

Electrocatalytic Reduction of Hydrogen Peroxide by Nanostructured Bimetallic Films of Metalloporphyrins

We report the sequential electrochemical deposition of bimetallic films of porphyrins onto gold nanoparticles, previously deposited by SAM on gold surface. SEM analysis of EAu/polyFeCuPP and EAu/cys/AuNp/polyFeCuPP showed a heterogeneous distribution of material aggregates in the former (ca. 0.1–1 μm), whereas the nanocomposite film exhibits a highly microporous structure in the micrometer diameter range. The sensitivity for H₂O₂ detection increased four times (609±6 mA M^?1 cm^?2 vs. 157±3 mA M^?1 cm^?2) with a linear relationship in the range of 1×10^?5–2×10^?3 M. The application of the particulate material to the first‐generation biosensor of glucose is described.     

Preparation and characterization of plasma-polymerized N-vinyl-2-pyrrolidone films

Thin films (< 1 μm) of plasma polymerized N-vinyl-2-pyrrolidone (PPNVP) have been prepared, using an inductively coupled RF glow discharge in a flow-through reactor system. PPNVP films were hydrophilic, smooth, and appeared morphologically homogeneous. The polymer deposition rate was found to increase linearly with NVP flow rate, and to decrease with the distance from the induction coil. ATR–FT–IR spectral studies suggested a highly branched polymer structure and included absorptions at 2150 and 1540 cm^?1 which were unique to the plasma polymer and derived from lactam ring opening/breaking reactions. ESCA studies demonstrated that, under a given set of plasma reaction conditions, the surface composition was consistent throughout the reactor. However, polymer composition was influenced by larger changes in the plasma energy, since the nitrogen content was found to decrease with increasing W/FM. This corresponded to concomitant increases in the advancing water contact angles and to small but reproducible changes in the IR spectrum.     

The dependence of the intensity of Raman bands of pyridine at a silver electrode on the wavelength of excitation

On increasing the wavelength of excitation over the range 350–700 nm, Raman bands of pyridine adsorbed at a roughened silver electrode are found to increase in intensity, relative to bands of the bulk medium (aqueous perchlorate or liquid pyridine) in contact with the electrode. The increase is observed in the bands at 1000–1050 cm^?1 and 1600 cm^?1 due to ring stretching, and similar increases are observed in other bands of the surface species, notably those due to CH stretching (3076 cm^?1), b₂ ring deformation (669 cm^?1, and AgN stretching (239 cm^?1, which have not been reported previously.     

Identification of carbonyl species of weathered LDPE films by curve fitting and derivative analysis of IR spectra

We describe the examination of the weathering degradation of LDPE (low density polyethylene - locally produced B24/2 and imported LDPE 2100T), supplied by two different manufacturers and processed into films for greenhouse coverings, over several months in a sub-Saharan region of Algeria. The three IR regions most affected by weathering degradation are 800–1100 cm⁻¹, 1680–1800 cm⁻¹ and 3300–3600 cm⁻¹. The IR spectral region most affected by the aging process is the carbonyl region. Curve fitting combined with derivative spectroscopy revealed that the composite carbonyl band encompasses more than 10 different oxidation products. The most significant among these in terms of absorbance are carboxylic acids, ketones, aldehydes and esters. The oxidation kinetics with respect to the type of LDPE film shows that B24/2 LDPE undergoes less oxidization than LDPE 2100 T. Calculating the concentrations of different carbonyl species compared to their respective absorbances indicates that the aldehydes are the predominant component of the final compound, rather than the carboxylic acids.     

Effect of stabilizers in the thermal treatment of PVC—X. An i.r. spectroscopic study of PVC with basic cadmium stearate

Infrared spectra (1900-1470 cm^?1) were studied for PVC films stabilized with basic Cd stearate and its mixture with stearic acid, after thermal degradation at 180° in air. Infrared spectroscopy makes it possible to follow the formation of Cd chloride-stearate on the basis of an absorption band at 1560–1565 cm^?1. The spectral data are compared with a potentiometric determination of HCl released from the mixture.     

IR spectra of long-chain α,ω-alkanediols: 1,22-docosanediol and 1,44-tetratetracontanediol

The IR absorption spectra of α,ω-alkanediols with different chain lengths, HO(CH₂)₂₂OH and HO(CH₂)₄₄OH, in the spectral range of 400–5000 cm^?1 are analyzed. The assignment of numerous absorption bands to vibration modes in short methylene sequences and terminal hydroxyl groups is suggested. The splitting of IR absorption bands into doublets at 720–730 cm^?1 (rocking vibrations of CH₂ groups) and 1463–1473 cm^?1 (bending vibrations of CH₂ groups) testifies that the crystal unit subcells in the lamellae of alkanediols are orthorhombic with parameters typical of normal hydrocarbons. The specific features of absorption bands due to O-H stretching and C-O-H bending vibrations have been analyzed. These bands appear during formation of lengthy associates from hydrogen bonds formed by hydroxyl groups on the surface of elementary lamellae. A sharp increase in the intensity of the absorption bands in progression of C-C stretching and CH₂ wagging vibrations due to the anharmonic Fermi resonance with the stretching vibrations of C-O groups in the terminal hydroxyl groups has been detected.     

Formation of quinoid fragments in vacuum-deposited poly-para-phenylene films: IR spectroscopy evidence

The structure of vacuum-deposited poly-para-phenylene (PPP) films prepared from a high-molecular-weight PPP powder has been investigated by IR spectroscopy. It has been demonstrated that in IR spectra of PPP films exhibiting intense luminescence an extremely strong band at 1375 cm⁻¹ is observed, which is not typical for currently known PPP modifications. Based on the IR spectral data, the model of formation of a PPP chain with quinoid fragments in the ground electronic state is proposed. The structure of defects that inevitably spring up during the benzenoid–quinoid transition is discussed. High intensity of the band at 1375 cm⁻¹ is associated with the change in the order of the “defect” C C bond between adjacent quinoid and benzenoid units. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1043–1052, 1998     

Interpretation of the IR spectrum of methyl-β-D-glucopyranoside based on the theoretical calculation of frequencies and intensities of normal vibrations

For the first time the detailed interpretation of the IR spectrum of methyl-β-D-glucopyranoside is presented based on the complete calculation of frequencies of normal vibrations and absolute intensities of IR absorption bands and on their comparison with the corresponding experimental values. The characteristic spectral features of oxymethyl substitution for the hydroxyl group are detected. The regularities in the formation of the complex band structure in a frequency range from 1150 cm^?1 to 950 cm^?1 is determined.     

Rutherford backscattering spectrometry studies of iodine diffusion in polyimide

Rutherford backscattering spectrometry with a 2.1-meV He²⁺ion beam is used to measure the diffusion of iodine into polyamic acid and polyimide films. The iodine diffusion coefficient D decreases from its initial value of about 2X10^?13cm²/s in polyamic acid to approximately 1.4 × 10^?15cm²/s in partially cured polyimide, but then increases to a value of nearly 1.5 × 10^?14 cm²/s in fully cured polyimide. This dramatic increase in D cannot be attributed to the “in-plane” biaxial orientation of the polyimide molecules since indential D's were found with isotropic specimens. Microvoids less than 2 nm in size caused by water and carbon dioxide formation during imidization may, however, give rise to the observed behavior. The results demonstrate that Rutherford backscattering spectrometry with its excellent depth resolution (better than 30 nm) and good sensitivity (50 ppm iodine can be detected) is very useful for measuring the diffusion of slowly diffusing species in glassy polymers.     

Chemical Factors That Influence the Production of Conductive and/or Reflective Silver-Doped Polyimide Films

ABSTRACT

Doping a poly(amide acid) resin with a silver containing additive (1,5-cyclooctadiene-hexafluoroacetylacetonato)-silver(I) [Ag(COD) (HFA)] resulted, after thermal cure, in either a highly reflective or highly eléctrically conductive polyimide film. The combination of monomers, which render films with low T_g (~210°C), and contained sulfur, produced films with surface resistance in the range 10^1–10³ ohms. On the other hand, films with specular reflectivity (relative to a silver mirror) in the range of 65–48% were obtained using both high T_g polyimides and polyimides void of sulfur in the polyimide backbone with low T_g. Our understanding regarding the structure-property relationship on these polyimide films and also the characterization of the doped-films are discussed.     

Infrared dichroism and molecular conformation of crystalline tetramethyldisiloxanediol

Vibrational spectra of tetramethyldisiloxanediol (TMDD) have been studied in solution and also in the solid state. Polarized IR spectra of oriented crystalline films have been recorded in the frequency range 4000–200 cm^?1. The structure of the molecules in solution has been found to be of C_2v symmetry. On the basis of the IR dichroitic data obtained for the oriented crystalline films, the molecules should have no symmetry in crystals (C₁ site symmetry) and the structure of OC₂SiOSiC₂O skeletal fragment may be described with an angle of torsion of about 70° around the (Si)O-Si bond.     

Intramolecular easily polarizable charged and non-charged hydrogen bonds: IR continua and hydrogen bond length

Substances with intramolecular, easily polarizable hydrogen bonds of different length are compared. Long hydrogen bonds cause IR continua which show band-like structures in the region 2800–1800 cm^?1, extending with weaker intensity toward smaller wave-numbers over the whole region studied. Medium length bonds cause continua beginning at 3200 cm^?1 and extending over the whole region studied. Very short, easily polarizable hydrogen bonds, such as the bond in the HAuCl₄ salt of NN'-tetramethyl-o-xylildiamine di-N-oxide, cause continua with very great intensity in the region 1500–850 cm^?1. Comparison of the experimental with calculated continua shows very good agreement with regard to wavenumber regions in which easily polarizable hydrogen bonds of different length cause IR continua.By comparing all these intramolecular, easily polarizable hydrogen bonds causing IR continua it is shown that the charge of the hydrogen bonds is not the decisive property for the occurrence of the continua but rather the shape of the proton potentials. Continua may occur only with hydrogen bonds with double minima or broad flat proton potential.     

Structure and molecular conformation of tussah silk fibroin films: Effect of methanol

Structural changes of tussah (Antheraea pernyi) silk fibroin films treated with different water-methanol solutions at 20°C were studied as a function of methanol concentration and immersion time. X-ray diffraction measurements showed that the α-helix structure, typical of untreated tussah films, did not change for short immersion times (2 min), regardless of methanol concentration. However, crystallization to β-sheet structure was observed following immersion of tussah films for 30 min in methanol solutions ranging from 20 to 60% (v/v). IR spectra of tussah films untreated and methanol treated for 2 min exhibited strong absorption bands at 1265, 892, and 622 cm^?1, typical of the α-helix conformation. The intensity of the bands assigned to the β-sheet conformation (1245, 965, and 698 cm^?1) increased for the sample treated with 40% methanol for 30 min. Raman spectra of tussah films with α-helix molecular conformation exhibited strong bands at 1657 (amide I), 1263 (amide III), 1106, 908, 530, and 376 cm^?1. Following α → β conformational transition, amide I and III bands shifted to 1668, and to 1241, 1230 cm^?1, respectively. The band at 1106 cm^?1 disappeared and new bands appeared at 1095 and 1073 cm^?1, whereas the intensity of the bands at 530 and 376 cm^?1 decreased significantly. ©1995 John Wiley & Sons, Inc.     

Correlation between IR spectra and electric conductivity of polyethylene-polypyrrole composites

Composite systems prepared via polymerization of pyrrole on PE porous films were studied by conductivity measurements and FTIR spectroscopy. The conductivity of samples was varied via dedoping of polypyrrole. The low-frequency edges of electronic absorption bands of quasi-particles responsible for the conductivity in polypyrrole appear in the IR spectral region. The total absorption is observed in the region of 650–15000 cm^?1 for the samples with a conductivity of 1–10 S/cm. A correlation was revealed between the position of the total absorption edge and the conductivity: the total absorption edge shifts to higher frequencies with a decrease in conductivity. On the basis of the data obtained, a model of the electronic structure of conductive polypyrrole is proposed.     

Synthesis and electroconductivities of poly(2-methoxy-5-methythio-1,4-phenylene vinylene) and copolymers

Poly(2-methoxy-5-methylthio-1,4-phenylene vinylene), PMTPV, and copolymers containing both unsubstituted or 2,5-dimethoxy-substituted and 2-methoxy-5-methylthio-1,4-phenylene vinylene units were prepared in thin films from their water-soluble, sulfonium salt precursor polymers. Doping of drawn and undrawn films of PMTPV with I₂ vapor led to conductivities of 10^?4–10^?3 S cm^?1, which is significantly lower than those reported for poly(2,5-dimethoxy-1,4-phenylene vinylene). Conductivity of I₂-doped copolymer films ranges from 10^?3–10⁰ S cm^?1 depending on composition.     

Vibrational Sum‐Frequency Generation Activity of a 2,4‐Dinitrophenyl Phospholipid Hybrid Bilayer: Retrieving Orientational Parameters from a DFT Analysis of Experimental Data

The vibrational nonlinear activity of films of 2,4‐dinitrophenyl phospholipid (DNP) at the solid interface is measured by sum‐frequency generation spectroscopy (SFG). Hybrid bilayers are formed by a Langmuir–Schaefer approach in which the lipid layer is physisorbed on top of a self‐assembled monolayer of dodecanethiol on Pt with the polar heads pointing out from the surface. The SFG response is investigated in two vibrational frequency domains, namely, 3050–2750 and 1375–1240 cm^?1. The first region probes the CH stretching modes of DNP films, and the latter explores the vibrational nonlinear activity of the 2,4‐dinitroaniline moiety of the polar head of the lipid. Analysis of the CH stretching vibrations suggests substantial conformational order of the aliphatic chains with only a few gauche defects. To reliably assign the detected SFG signals to specific molecular vibrations, DFT calculations of the IR and Raman activities of molecular models are performed and compared to experimental solid‐state spectra. This allows unambiguous assignment of the observed SFG vibrations to molecular modes localized on the 2,4‐dinitroaniline moiety of the polar head of DNP. Then, SFG spectra of DNP in the 1375–1240 cm^?1 frequency range are simulated and compared with experimental ones, and thus the 1,4‐axis of the 2,4‐dinitrophenyl head is estimated to have tilt and rotation angles of 45±5° and 0±30°, respectively.