Physicochemical Properties of Polyaniline Base and Salt Films

Abstract

Polyaniline base and perchlorate salt films cast from N-methylpyr-rolidinone (NMP) solutions are studied using thermogravimetric analysis, infrared and ultraviolet-visible absorption spectroscopy, and x-ray photoelectron spectroscopy. Both types of films retain a substantial amount of solvent. Although most of the solvent can be removed by washing the films with deionized water, some C1O^? ₄ anions are removed from the salt films as well, resulting in a decrease in conductivity. In the salt films, protonation of the amine units in addition to the imine units can be readily achieved using HC1O₄. Structural modifications of the base films are apparent after one reprotonation/deprotonation cycle. These result in a decrease in the solubility of the film, the extent of which increases with the protonation level. Although NMP is a useful solvent for casting polyaniline salt and base films, both leucoemeraldine and perchloric acid protonated salt undergo degradation in this solvent.     

Kinetics and Mechanism for Hydrolysis of α-Amino Acid Esters in Mixed Ligand Complexes with Zn(II)–Nitrilo-tris(methyl phosphonic Acid)

The kinetics of base hydrolysis of the alanine ethyl ester, in addition to glycine, histidine and methionine methyl esters in the presence of the Zn-NTP complex, were studied in aqueous solution by the pH-potentiometric technique, where NTP denotes the nitrilo-tris(methyl phosphonic acid) ligand. The kinetic data fits assumed that hydrolysis proceeds through formation of a M–OH complex, followed by an intramolecular OH⁻ attack. The effect of an organic solvent on the hydrolysis of coordinated esters was investigated by measuring the rate of hydrolysis in dioxane–water solutions of different compositions at t=25.0 °C and I=0.1 mol⋅dm⁻³. The kinetics of base hydrolysis of the glycine methyl ester was studied at different temperatures. Activation parameters for the base hydrolysis of the complexes were evaluated.     

Retardation Effect of Enzymatic Degradation of Microbial Polyesters at the Surface by Blending with Polystyrene

The enzymatic surface degradation behavior of the blend films of polystyrene (PS) with poly[((R)‐3‐hydroxybutyrate)‐co‐((L )‐3‐hydroxyvalerate)] (P(3HB‐co‐3HV)) or poly((R)‐3‐hydroxybutyrate (P(3HB)) were investigated using atomic force microscopy (AFM). It was found that the blends of PS with P(3HB‐co‐3HV) or P(3HB) are immiscible in both the amorphous and melt states. The degradation of both P(3HB‐co‐HV) and P(3HB) was significantly retarded at the initial stages of enzymatic attack by hydrophobic PS (up to 20 wt.‐%).     

Double/single phase segregation and vertical stratification induced by crystallization in all‐crystalline tri/diblock copolymers and homopolymer blends of poly(3‐hexylthiophene) and poly(ethylene glycol)

Distinct stratified and non‐stratified morphologies were developed in poly(3‐hexylthiophene) (P3HT) and poly(ethylene glycol) (PEG)‐based homopolymer blends and diblock and triblock copolymer systems. By applying X‐ray photoelectron spectroscopy, only a double‐percolation mechanism including assembling of P3HT chains into the nanofibers in solution aging process with a marginal solvent like p‐xylene as well as crystallization of PEG phase in the cast thin films resulted in vertical stratification and networked fibrils. In cast thin films whose PEG phase, due to low molecular weight or being constrained between two rigid P3HT blocks in triblock copolymers was not crystallized, a non‐stratified discrete fibrillar morphology was acquired. Crystallization of PEGs in the thin films mainly participated in networking and expelling pre‐organized P3HT fibrils to the film surface. By performing the solution aging step in a good solvent such as o‐dichlorobenzene, the P3HTs remained in a coily‐like conformation, and casting the corresponding thin films reflected the non‐stratified discrete granular and featureless morphologies. Assembling the P3HT chains in the presence of PEG phase in cast films at most led to the low‐crystalline granules instead of highly crystalline nanofibrils. No significant crystallization in either homopolymer blends or block copolymer systems conduced to a featureless morphology with homogeneous distribution of existed materials. The surface morphology and ordering in various morphologies were studied employing atomic force microscopy, grazing incidence X‐ray diffraction, and ultraviolet–visible analyses. Copyright © 2016 John Wiley & Sons, Ltd.     

Polycondensation behavior of methyltrimethoxysilane studied by NMR spectroscopy

Silicate gels are most often synthesized by hydrolyzing monomeric alkoxide precursors employing acid or base catalysts. The properties of final products are determined by the pathway of the reactions, which includes hydrolysis, condensation, and solvent exchange reaction. We analyzed a system with methyltrimethoxysilane as monomer and ethanol as solvent by using ¹H, ¹³C, and 2D heteronuclear correlated nuclear magnetic resonance (NMR) spectroscopy. Complete assignments of the proton and the ¹³C-NMR bands were established, which rendered the kinetic study feasible. An understanding of the behavior of the system was also attempted, especially at earlier stages. The results showed that hydrolysis and solvent exchange reactions occurred at early stage whereas condensation occurred slowly. © 1996 John Wiley & Sons, Inc.     

Mechanical properties, structure analysis and enzymatic degradation of uniaxially cold-drawn films of poly[(R)-3-hydroxybutyrate-co-4-hydroxybutyrate]

Poly[(R)-3-hydroxybutyrate-co-4-hydroxybutyrate] (P(3HB-co-4HB)) films were prepared by uniaxial cold-drawing from an amorphous preform at a temperature below, but close to the glass transition temperature. Molecular and highly-ordered structures and physical properties of cold-drawn films were investigated by tensile testing, wide-angle X-ray diffraction and small-angle X-ray scattering. Enzymatic degradation of P(3HB-co-4HB) films was performed using an extracellular polyhydroxybutyrate depolymerase purified from Ralstonia pickettii T1. Tensile strength, elongation to break and Young’s modulus of P(3HB-co-4HB) with cold-drawn ratio 1200% reached 290 MPa, 58% and 2.8 GPa, respectively. X-ray fibre diagrams of cold-drawn P(3HB-co-4HB) films showed a strong reflection on the equatorial line, indicating a planar zigzag conformation (β-form) together with 2₁ helix conformation (α-form). The β-form seems to contribute to the high tensile strength, and a new mechanism of generation of the β-form is proposed. The enzymatic degradation rate increased with increasing draw ratio, and increased greatly with increasing 4HB content.     

Zur Natur der Aluminiumsilicatniederschläge aus Na2H2SiO4-und AlCl3-Lösungen bei neutraler Reaktion

On addition, at neutral reaction, of increasing amounts of AlCl₃ solutions to 0.005 m Na-silicate solutions, in which the silicate anions are monomeric, amorphous, almost Na⁺-free precipitates are formed being at first characterised by a higher atomic Al:Si ratio than the total Al:Si mixing ratio. With increasing Al:Si addition, the Al:Si ratio of the precipitates increases until — at a 3:1 ratio in both the liquid and the solid phase — a definite, “saturated” compound, {[(OH)₂AlO]₃SiOH · aq}, is formed. In this compound the silicate anions are monomeric and not condensable at room temperature. This is valid, too, for precipitates from Al:Si > 3 which contain, besides the “saturated” compound, free Al hydroxide. The first-mentioned precipitates with Al:Si < 3, however, contain polymeric Si units which easily condense to more high-polymeric silicate anions.     

Alkaline and enzymatic degradation of L‐lactide copolymers. II. Crystallized films of poly(L‐lactide‐co‐D‐lactide) and poly(L‐lactide) with similar crystallinities

Films of poly(L ‐lactide‐co‐D ‐lactide) [P(LLA‐DLA); 95/5] and poly(L ‐lactide) [i.e., poly(L ‐lactide acid) (PLLA)] were prepared by crystallization from the melt, and a comparative study of the crystallization effects on the alkaline and proteinase K catalyzed hydrolysis of the films was carried out. The hydrolyzed films were investigated with gravimetry, differential scanning calorimetry, polarimetry, and gel permeation chromatography, and the results were compared with those reported for amorphous‐made specimens. The alkaline hydrolyzability of the P(LLA‐DLA) (95/5) and PLLA films was determined solely by the initial crystallinity (X_c) and was not affected by the content of the incorporated D ‐lactide (DLA) unit in the polymer chain; this was in marked contrast to the fact that the enzymatic hydrolyzability depended on not only the initial X_c value but also the DLA unit content. The alkaline hydrolysis rate of the P(LLA‐DLA) (95/5) and PLLA films and the enzymatic hydrolysis rate (R_EH) of the P(LLA‐DLA) (95/5) films decreased linearly as the initial X_c value increased. This meant that the hydrolyzability of the restricted amorphous regions was very similar to that of the free amorphous regions. In contrast, R_EH of the PLLA films decreased nonlinearly with the initial X_c value, and this nonlinear dependence was caused by the fact that in the PLLA films the restricted amorphous regions were much more hydrolysis‐resistant than the free amorphous regions. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1064‐1075, 2005     

13C and 1H amorphous linewidths in semicrystalline poly(4-hydroxybutyrate) and poly(3-co-4-hydroxybutyrate) above Tg by high resolution and solid-state NMR experiments

The high-resolution ¹³C and ¹H nuclear magnetic resonance (NMR) linewidths of semi-crystalline poly(4-hydroxybutyrate), P4HB, and poly(3-hydroxybutyrate-co-4-hydroxybutyrate), (P3/4HB-18, 18% 4HB units) in the amorphous phase and in the melt are studied as a function of temperature and magnetic field strength. Measurements of the ¹³C spin-spin relaxation times under the same experimental conditions show that the natural line-width is a minor contributor to the line-broadening observed in the ¹³C spectra of the solid polymers. A variety of coherent averaging solid-state NMR methods are used to examine possible contributions from various line-broadening mechanisms. It is shown that magnetic susceptibility and chemical shift dispersion are the major factors for the broadening of the proton and carbon resonances of P4HB in the amorphous phase and the melt, respectively. Incomplete motional narrowing due to a slow motional mode restricted in amplitude by the presence of crystallites and/or chain constraints was found to be the major line-broadening factor for P3/4HB-18 in the amorphous phase. Correlations between crystalline morphology, physical and mechanical properties, and polymer chain dynamics are discussed, along with the way these factors affect the NMR linewidth data presented. © 1996 John Wiley & Sons, Inc.     

Enhancement of Stress Tolerance in the Polyhydroxyalkanoate Producers without Mobilization of the Accumulated Granules

Poly(3-hydroxybutyrate) [P(3HB)], a polymer belonging to the polyhydroxyalkanoate (PHA) family, is accumulated by numerous bacteria as carbon and energy storage material. The mobilization of accumulated P(3HB) is associated with increased stress and starvation tolerance. However, the potential function of accumulated copolymer such as poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] remained unknown. In this study, Delftia acidovorans DS 17 was used to evaluate the contributions of P(3HB) and P(3HB-co-3HV) granules during simulated exogenous carbon deprivation on cell survival by transferring cells with PHAs to carbon-free mineral salt medium supplemented with 1 % (w/v) nitrogen source. By mobilizing the intracellular P(3HB) and P(3HB-co-3HV) at 11 and 40 mol% 3HV compositions, the cells survived starvation. Surprisingly, D. acidovorans containing P(3HB-co-94 mol% 3HV) also survived although the mobilization was not as effective. Similarly, recombinant Escherichia coli pGEM-T::phbCAB _Cn (harboring the PHA biosynthesis genes of Cupriavidus necator) containing P(3HB) granules had a higher viable cell counts compared to those without P(3HB) granules but without any P(3HB) mobilization when exposed to oxidative stress by photoactivated titanium dioxide. This study provided strong evidence that enhancement of stress tolerance in PHA producers can be achieved without mobilization of the previously accumulated granules. Instead, PHA biosynthesis may improve bacterial survival via multiple mechanisms.     

Use of in‐situ atomic force microscopy to monitor the biodegradation of polyhydroxyalkanoates (PHAs)

Thin films of a co‐polymer mixture of poly 3‐hydroxybutyrate and poly 3‐hydroxyvalerate P(3HB‐3HV) were spun‐cast onto glass slides resulting in 35 nm thick layers with a spherulitic microstructure. An untyped strain of Streptomyces sp. bacteria was isolated from soil samples, and it's PHA depolymerase was used to degrade the P(3HB‐3HV) thin films. Both ex‐situ and in‐situ atomic force microscopy (AFM) biodegradation studies were performed to determine the kinetics of the biodegradation over the course of three hours at room temperature. Ex‐situ AFM was performed in Tapping Mode and in‐situ AFM was performed in the PHA depolymerase using contact mode AFM in the liquid cell, allowing for the real‐time analysis of P(3HB‐3HV) biodegradation. Biodegradation is observed uniformly throughout the surface, and can be observed within 30 min. of depolymerase exposure. In‐situ AFM analysis yields a linear degradation rate as a function of time, while the ex‐situ study suggests a more complex kinetics.     

Enzymatic biodegradation of chemosynthetic atactic P(3HB) enhanced by an amorphous non‐biodegradable polymer: blend of atactic P(3HB) with PMMA

Communication: The phase structure and biodegradability were investigated for a blend of chemosynthetic atactic poly((R,S)‐3‐hydroxybutyrate), a‐P(3HB), and poly(methyl methacrylate), PMMA. The thermal analysis indicated that amorphous a‐P(3HB)/PMMA blends with 20 wt.‐% and 40 wt.‐% PMMA shows sophisticated phase behavior and is partially miscible. The depolymerase of natural poly((R)‐3‐hydroxybutyrate) purified from Alcaligenes faecalis T1 did not degrade chemosynthesized a‐P(3HB) at all in the pure state, but it degraded a‐P(3HB) in some a‐P(3HB)/PMMA blends. The results suggested that enzymatic degradation of a‐P(3HB) can be enhanced by an amorphous non‐biodegradable polymer.     

Bulk Gas‐Phase Acidity

The capability of a gaseous Brønsted acid HB to deliver protons to a base is usually described by the gas‐phase acidity (GA) value of the acid. However, GA values are standard Gibbs energy differences and refer to individual gas pressures of 1 bar for acid HB, base B^?, and proton H⁺. We show that the GA value is not suited to describe the bulk acidity of a gaseous acid. Here the pressure dependence of the activities of HB, H(HB)_n⁺, and B(HB)_m^? that result from gaseous autoprotolysis have to be considered. In this work, the pressure‐dependent absolute chemical potential of the proton in the representative gaseous proton acids CH₄, NH₃, H₂O, HF, and HCl was worked out and the general theory to describe bulk gas phase acidity—that can directly be compared with solution acidity—was developed.     

Preparation of plasma-films containing carboxylate anions by hydrolysis with octylbromide

To obtain thin films containing carboxylate anions, hydrolysis of amido groups in films plasma-polymerized from trimethylsilyldimethylamine (TMSDMA) and bis(dimethylamino)methylvinylsilane (BDMAMVS) has been investigated by infrared spectroscopy and ESCA. The thin films from TMSDMA and BDMAMVS were hydrolyzed at 80–100°C for 3–16 h to transform amido groups to carboxyl groups. The products hydrolyzed from the TMSDMA–plasma-polymers were mixtures of carboxylate ester and carboxylic acid, and that from the BDMAMVS–plasma-polymers was carboxylic acid. The hydrolysis reaction was restricted at regions near polymer surfaces.     

Controlling the surface composition of PCBM in P3HT/PCBM blend films by using mixed solvents with different evaporation rates

The surface composition of poly(3-hexylthiophene-2,5-diyl) and fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (P3HT/PCBM) blend films could be changed by controlling the film formation process via using mixed solvents with different evaporation rates. The second solvent, with a higher boiling point than that of the first solvent and much better solubility for PCBM than P3HT, is chosen to mix with the first solvent with a lower boiling point and good solubility for both PCBM and P3HT. The slow evaporation rate of the second solvent provides enough time for PCBM to diffuse upwards during the solvent evaporation. Thus, the weight ratio of PCBM and P3HT (m _PCBM/m _P3HT) at surface of the blend films was varied from ca. 0.1 to ca. 0.72, i.e., it increases about seven times by changing from single solvent to mixed solvents. Meanwhile, the mixed solvents were in favor to form P3HT naonofiber network and enhance phase separation of P3HT/PCBM blend films. As a result, the power conversion efficiency of the device from mixed solvents with slow evaporation process was about 1.5 times of the one from single solvents.     

Effects of evaporation velocity and film thickness on poly(3‐hexylthiophene) thin films processed from aggregate dispersions in binary solvent mixtures

Aggregate dispersions of P3HT in two series of solvent mixtures, chloroform:dichloromethane and toluene:dichloromethane, are used to study the impact of the evaporation velocity and film thickness on the P3HT films processed using two spin‐coating speeds (1000 rpm and 2000 rpm). The structural order and surface morphology were investigated with UV/Vis absorption spectroscopy and atomic force microscopy techniques. There is no evidence that the characteristics of the liquid phase P3HT dispersions impact the structures of the films, which is in agreement with a previous study of drop cast P3HT films that were dried over much longer time periods. An association is observed between the extent of aggregation in the liquid phase and the thickness and surface roughness parameters of the films. However, the structural order does not correlate with the thickness of the films, which was previously reported for polymer films processed from amorphous polymer solutions in pure organic solvents. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 330–343     

Formation of Zn–Al layered double hydroxide thin films intercalated with sulfonated spiropyran

We prepared Zn–Al layered double hydroxide (LDH) thin films intercalated with sulfonated 1,3′,3′-trimethyl-6-nitrospiro[2H-chromene-2,2′-indoline] anions (SP-SO₃ ^?) by immersion of sol–gel derived amorphous Al₂O₃–ZnO thin films in hot water containing SP-SO₃H. Extended interlayer spacing, in comparison to the Zn–Al LDH with carbonate anions, was observed after immersion in distilled water containing SP-SO₃H at 60 °C for 30 min, indicating that we formed Zn–Al LDH films with SP-SO₃ ^? directly on glass substrates. The merocyanine form of SP-SO₃ ^? was shown by UV spectra to have stabilized in the hydroxide layers of LDH.     

Schiff Base Structured Acid–Base Cooperative Dual Sites in an Ionic Solid Catalyst Lead to Efficient Heterogeneous Knoevenagel Condensations

An acid–base bifunctional ionic solid catalyst [PySaIm]₃PW was synthesized by the anion exchange of the ionic‐liquid (IL) precursor 1‐(2‐salicylaldimine)pyridinium bromide ([PySaIm]Br) with the Keggin‐structured sodium phosphotungstate (Na₃PW). The catalyst was characterized by FTIR, UV/Vis, XRD, SEM, Brunauer–Emmett–Teller (BET) theory, thermogravimetric analysis, ¹H NMR spectroscopy, ESI‐MS, elemental analysis, and melting points. Together with various counterparts, [PySaIm]₃PW was evaluated in Knoevenagel condensation under solvent and solvent‐free conditions. The Schiff base structure attached to the IL cation of [PySaIm]₃PW involves acidic salicyl hydroxyl and basic imine, and provides a controlled nearby position for the acid–base dual sites. The high melting and insoluble properties of [PySaIm]₃PW are relative to the large volume and high valence of PW anions, as well as the intermolecular hydrogen‐bonding networks among inorganic anions and IL cations. The ionic solid catalyst [PySaIm]₃PW leads to heterogeneous Knoevenagel condensations. In solvent‐free condensation of benzaldehyde with ethyl cyanoacetate, it exhibits a conversion of 95.8 % and a selectivity of 100 %; the conversion is even much higher than that (78.2 %) with ethanol as a solvent. The solid catalyst has a convenient recoverability with only a slight decrease in conversion following subsequent recyclings. Furthermore, the new catalyst is highly applicable to many substrates of aromatic aldehydes with activated methylene compounds. On the basis of the characterization and reaction results, a unique acid–base cooperative mechanism within a Schiff base structure is proposed and discussed, which thoroughly explains not only the highly efficient catalytic performance of [PySaIm]₃PW, but also the lower activities of various control catalysts.     

A sol-gel route for the development of rare-earth aluminum borate nanopowders and transparent thin films

A new sol-gel route was applied to obtain Y_0.9Er_0.1Al₃(BO₃)₄ crystalline powders and amorphous thin films by using Al(acac)₃, B(OPrⁱ)₃, Y(NO₃)₃·6H₂O, and Er(NO₃)₃·5H₂O as starting materials dissolved in propionic acid and ethyl alcohol mixtures. Our study shows that propionic acid acts as good chelant agent for yttrium and erbium ions while ethyl alcohol allows to dissolve Al(acac)₃. This process makes the resulting sols very stable to obtain homogeneous gels and transparent amorphous thin films. In addition, the propionic acid prevents the sol precipitation, making easy porous- and crack-free thin film depositions. Chemical reactions involved in the complexation were discussed. As-prepared powders and films are amorphous and present a good thermal stability due to their high glass transition (746 °C) and crystallization temperatures (830 °C). This new sol-gel route showed to be adequate to obtain dense and crack-free thin films free of organic and hydroxyl groups that can be considered as promising materials to be used in integrated optical systems.     

X-ray absorption fine structure study of amorphous metal oxide thin films prepared by photochemical metalorganic deposition

The oxidation state and local geometry of the metal centers in amorphous thin films of Fe₂O₃ (Fe³⁺ oxidation state), CoFe₂O₄ (Co²⁺/Fe³⁺ oxidation states), and Cr₂O₃ (Cr³⁺ oxidation state) are determined using K edge X-ray absorption near-edge structure (XANES) spectroscopy and extended X-ray absorption fine structure (EXAFS) spectroscopy. The metal oxide thin films were prepared by the solid-state photochemical decomposition of the relevant metal 2-ethylhexanoates, spin cast as thin films. No peaks are observed in the X-ray diffraction patterns, indicating the metal oxides are X-ray amorphous. The oxidation state of the metals is determined from the edge position of the K absorption edges, and in the case of iron-containing samples, an analysis of the pre-edge peaks. In all cases, the EXAFS analysis indicates the first coordination shell consists of oxygen atoms in an octahedral geometry, with a second shell consisting of metals. No higher shells are observed beyond 3.5 Å for all samples, indicating the metal oxides are truly amorphous, consistent with X-ray diffraction results.