Thermal Degradation of Poly(ε-caprolactone), Poly(L-lactic acid) and their Blends with Poly(3-hydroxy-butyrate) Studied by TGA/FT-IR Spectroscopy

Summary: The thermal degradation behavior of poly(ε-caprolactone) (PCL) and poly(L-lactic acid) (PLA) have been studied in different environment. It was found that these polymers undergo completely different degradation processes in nitrogen and oxygen atmosphere. In oxygen environment PCL and PLA mainly decompose to CO₂, CO, water and short-chain acids. In nitrogen atmosphere PCL releases 5-hexenioc acid, CO₂, CO and ε-caprolactone, whereas PLA decomposes to acetaldehyde, CO₂, CO and lactide. The polymer blends of poly(3-hydroxybutyrate) (PHB) with PCL and PLA decompose similar to the individual homopolymers with crotonic acid as the initial decomposition product of PHB.     

Raman Spectroscopic Study of the Conformation and Melting of Poly(dG) · Poly(dC) and Poly(dG-dC) · Poly(dG-dC) in Aqueous Solution

Raman spectroscopic measurements on aqueous solutions of poly(dG) · poly(dC)indicate that the conformation of the polynucleotides in this double helicalcomplex are distributed between the A and B types at room temperature, the Aform being predominant at –15°C and decreasing progressively upon raising thetemperature to 65°C. A reversible pretransition has been found in this complexnear 70°C. Modifications in the spectra at this temperature indicate no majorconformational changes, but rather suggest altered base pairing and hydration ofthe carbonyl groups, accompanied by a slight distortion of the double helix,resulting in a slightly reduced stacking of the cytosine bases. Measurements inself-pressurized solutions of the complex at high temperature show that it meltsat 103°C in 0.1M NaCl solution (107°C in 0.5M NaCl). These values are somewhatlower than those we have determined in the same manner for the complexpoly(dG-dC) · poly(dG-dC): 117°C in 0.1M MgCl₂ and 113°C or higher in 0.1MNaCl solution.     

Preparation and characterization O-lauroyl chitosan/poly (L-lactic acid) blend membranes by solution-casting approach

O-Lauroyl chitosan/poly(L-lactide) (OCS/PLLA) blend membranes with different compositions were prepared by solution-casting approach using chloroform as common solvent. The experimental results of FT-IR, DSC and WAXD indicated that inter-association hydrogen-bond interactions existed between OCS and PLLA in the blend membranes. And SEM observation confirmed that the blend membranes with suitable compositions were compatible.     

Probing the Effects of Antimicrobial-Lysozyme Derivatization on Enzymatic Degradation of Poly(ε-caprolactone) Film and Fiber

Surface derivatization is essential for incorporating unique functionalities into biodegradable polymers. Nonetheless, its precise effects on enzymatic biodegradation still lack comprehensive understanding. In this study, a facile solution-based method is employed to surface derivatize poly(ε-caprolactone) films and electrospun fibers with lysozyme, aiming to impart antimicrobial properties and examine the impact on enzymatic degradation. The derivatized films and fibers have shown high antibacterial efficacy against Escherichia coli and Staphylococcus aureus. Through gravimetric analysis, it is observed that the degradation rate experiences a slight decrease upon lysozyme derivatization. However, this reduction is effectively countered by the inclusion of Tween-20, as affirmed by isothermal titration calorimetry. Comparing films and fibers, the latter undergoes degradation at a more accelerated pace, coupled with a rapid decline in molecular weight. This study provides valuable insights into the factors influencing the degradation of surface-derivatized biopolymers through electrospinning, offering a simple strategy to mitigate biomaterial-associated infections.     

Parameters and Form of the Mössbauer Spectra of Iron(III) β-Diketonates: New Data

Mössbauer spectra have been measured at 295 and 78 K for ten ⁵⁷Fe-enriched iron(III) -diketonates differing in the type of radical in the chelate ring. Since the literature data for compounds of this class are incomplete and contradictory, a repeated analysis of spectrum shape and parameters has been performed. The chemical shift and quadrupole splitting are virtually independent of the type of radical in the chelate ring whereas the line width and asymmetry exhibit a pronounced dependence on the temperature and composition of the compounds. The available concepts on the nature of quadrupole splitting and relaxation mechanisms determining the lineshape for the given compounds are refined. It is concluded that electron spin relaxation is longitudinal or transverse relative to the principal axis of the electric field gradient in different compounds.     

The Study of the Reaction Mechanism for the Dehydrogenation of Ethylbenzene on Iron Oxide Catalysts (Ⅰ)——IR Spectra of Adspecies and Kinetic Isotope Effects

In situ PT-IR spectroscopy was used to examine ethylbenzene adspecies on iron-oxide-besed catalysts,and the method of kinetic isotope effects was used to investigate the rate determining step of the dehydrogenation.A possible reaction mechanism is proposed.     

Modeling of the Electronic Absorption Spectra and Photoionization of Scandium and Titanium Tris(acetylacetonates) by the DV-XαMethod

In order to interpret the electronic absorption spectra of titanium tris(-diketonates) and to establish the correlation between the ionization and excitation energies, the oscillator strengths and energies and the ionization energies for the model complexes M(Mal)₃(Mal is deprotonated malonodialdehyde, M = Sc, Ti) were calculated in the transition state approximation of the DV-Xmethod. The good agreement between the calculated photoelectron spectra and the experimental data and the correlation found between two types of excitation justified the assignment of the experimental absorption bands to the electronic states of Ti(Acac)₃.     

Removal of Lead (II) Ions by Poly(2‐octadecyl butanedioic acid): Isothermal and Kinetic Studies

Poly(2‐octadecyl‐butanedioic acid), prepared from polyanhydride PA‐18, possesses novel heavy metal adsorption characteristics. The adsorption capacity of this water insoluble polymer for lead (II) was substantially higher than other heterogeneous adsorbants and is equivalent to those obtained with homogeneous sorbants. The polymer exhibited pseudo‐second‐order kinetics and nearly complete adsorption of lead occurred in 15 min with initial lead (II) concentrations greater than 100 mg · L^?1. Adsorptive behavior was accurately predicted by the Dubinin‐Radushkevich isotherm model. The mean free energy of adsorption of lead (II) onto poly(2‐octadecyl‐butanedioic acid) was determined to be 31.6 kJ · mol^?1, suggesting an ion exchange component to the adsorption mechanism. Gibb's free energy values for this process indicate that it is spontaneous. Adsorption was relatively independent of pH in the range of 3–5, due to the utilization of the sodium carboxylate form of the chelating groups, and was not influenced by high Na⁺ concentration and moderate concentrations (up to 200 mg · L^?1) of Ca⁺². Lead (II) solutions containing 2000 mg · L^?1 Ca⁺² did reduce the adsorption of 2000 mg · L^?1 lead (II) by 28%.     

Poly(aminohippuric acid)–sodium dodecyl sulfate/functionalized graphene oxide nanocomposite for amplified electrochemical sensing of gallic acid

Gallic acid (GA), as a main phenolic acid, has been considered the main player on the human health, including the effects of reduction of cholesterol, depression of hypertension, anti-oxidation, anti-microbial, protection against cardiovascular disease and cancer. This study describes the development, electrochemical characterization and utilization of a novel functionalized graphene oxide/poly(p-aminohippuric acid)–sodium dodecyl sulfate nanocomposite modified glassy carbon electrode (APTS@GO/PPAH-SDS/GCE) for the electrocatalytic determination of GA. The synthesized nanocomposite was characterized by different techniques such as Fourier-transform infrared spectroscopy, thermo-gravimetric analysis and transmission electron microscopy. The electrochemical oxidation of GA was investigated by cyclic voltammetry, differential pulse voltammetry and amperometry. The modified electrode showed a potent and persistent electron mediating behavior followed by well-defined oxidation peak of GA and the linear range of 0.006–2000 µmol L^?1 with a detection limit of 1.7 nmol L^?1 for GA (S/N?=?3) using amperometric method. Also, it was successfully used for the GA determination in the black tea and tab water as real samples. Additionally, this electrode exhibited good stability and reproducibility. The results imply that the APTS@GO/PPAH-SDS nanocomposite might be a promising candidate for practical applications in GA electrochemical detection.     

Poly(2-vinylpyridine) as a template for the radical polymerization of methacrylic acid—VI. Influence of the solvent

The template polymerization (TP) of methacrylic acid (MAA) along poly(2-vinylpyridine) (P2VP) has been investigated to study effects of solvent polarity upon the kinetics. The solvents were DMSO, DMF and dioxane. In DMSO, there is no rate enhancement due to the presence of the template; this is consistent with the fact that poly(methacrylic acid) (PMAA) and P2VP do not form complexes in this strongly solvating medium. The rate enhancement (template effect) in DMF is primarily due to termination retardation of P2VP-bound PMAA radicals. The largest template effect was found in 1,4-dioxane (about three times that in DMF). The cause may be the faster complexation of PMAA-radicals to the template (ca 10 times that in DMF). The non-steady state conditions for the template radical concentration, which is an essential aspect for the estimation of the various rate coefficients of the proposed kinetic model for TP, could be confirmed with EPR-measurements.     

Analysis of pigments and coverings by X-ray diffraction (XRD) and micro Raman spectroscopy (MRS) in the cemetery of Tutugi (Galera, Granada, Spain) and the settlement convento 2 (Montemayor, Córdoba, Spain)

This paper focuses on the identification of the composition of the coverings and pigments of two archaeological sites. The sites researched here lie in Andalusia and show two contexts, which have a highly symbolic and ritual meaning. The first, Convento 2 (Montemayor, Córdoba), dates back to the period of formation of the Iberian Culture (VIIth century b.c.). The second is the cemetery of Tutugi (Galera, Granada), of the mid-Iberian period (IVth century b.c.). The analytical procedure consisted in combined and complementary use of XRD and MRS. This allowed to identify the materials used, namely hematite, goethite, coal, gypsum and calcite. Identification of these materials proves essential for the restoration and musealization of both archaeological sites.     

Determination of Electron and Hole Mobility of Regioregular Poly(3‐hexylthiophene) by the Time of Flight Method

Time of flight method (TOF) is used to measure the electron and hole mobility of a spin coated regioregular poly(3‐hexylthiophene) (P3HT) film. We find that both electron and hole have the same mobility (about 3.8～3.9×10^?4 cm²/Vs) at an applied field of 120 kV/cm. It is demonstrated in this paper that the electron‐hole recombination process may prevent the electron transport in the material due to the fact that the carrier recombination time is much shorter than the transit time.     

Study of the structure of (carbamimidoylsulfanyl)acetic (“pseudothiohydantoic”) acid by XRD and PM6 methods

It was shown by the method of powder X-ray diffraction analysis that in the crystalline state the product of the reaction of thiourea with chloroacetic acid in water, (carbamimidoylsulfanyl)acetic acid, existed in the zwitter-ion tautomeric form. The structure consists of virtually planar infi nite layers normal to the c axis of the unit cell which are bound by van der Waals interactions. The layers are formed by infi nite rows elongated along the b axis of the unit cell consisting of materially planar zwitter-ionic molecules linked by strong bifurcated hydrogen bonds. The results of quantum-chemical calculations by PM6 method are in agreement with the XRD results: whereas an isolated molecule exists in nonzwitter-ionic tautomeric form, in the crystal only the zwitterionic tautomer is present.     

Adsorptive Stripping Voltammetric Study of the Enhancement of Copper(Ⅱ) by Poly(vinyl alcohol), Starch and Polyallylamine

l.IntroductionAsalatelydeveloPedsensihveandsimPleelectroanalghcalmethod,adsorptivedrippingvoltanUneto'(AdSV)receivesincreasingattenhonIl,2a].lnorgamcionscanbedetetrinedincomPlexformb}'AdSV,andmoStligandsusedaresmal1orgtricmoleculeswhichcanbeadsoIbedonthesdriceofelectrodereadily[2b]fforinStance,beryllonIIIisfitforthedetenTiltalonofboron[31.AJthoughwater-solublePOlyInerssuchasPOly(vinylalcohol)WVA)areusedasenhancingreagentSinvoltaInInetryformetalcomPlexesofotherligands[4],therearenor…     

Intensity of the η(C≡C) Bands in the IR Spectra of Acetylene Derivatives and σR 0 Constants of Organosilicon,Organogermanium, and Organotin Substituents

The integral absorptivities of shape-characteristic (CC) bands in the IR spectra of 66 acetylene derivatives RCCX (R = H, Me₃M; X are inorganic and organic substituents) are related by a common linear equation to the _R ⁰ constants of the R and X substituents. The _R R⁰ constants of 10 Alk₃M substituents were calculated. The _R ⁰, _R , and _R ⁺ constants of Me₃M substituents were analyzed. The positive _R ⁰ values (0.12, 0.06, and 0.04 for R = Si, Ge, and Sn, respectively) suggest that in the ground electronic state of Me₃MCCX molecules the resonance acceptor effect of the Me₃M substituents (d, conjugation) prevails over donor (, conjugation). The first effect attenuates and the second enhances as the atomic number of M increases.     

Development of Electrochemical Platform Based on Molecularly Imprinted Poly(methacrylic acid) Grafted on Iniferter-modified Carbon Nanotubes for 17β-Estradiol Determination in Water Samples

This paper describes the development of a new electrochemical sensor for 17β-estradiol (E2) determination based on glassy carbon electrode (GCE) modified with molecularly imprinted polymer grafted onto iniferter-multiwall carbon nanotubes surface (MIP-MWCNT) and dihexadecyl-hydrogen-phosphate (DHP). The electrochemical method was based on closed-circuit preconcentration of E2 in 0.1 mol L⁻¹ phosphate buffer (pH 7.0) during 500 s. Upon preconcentration, E2 was determined by differential pulse voltammetry (DPV) exhibiting a limit of detection of 0.01 μmol L⁻¹. The sensor exhibited higher selectivity toward E2 and it was applied for E2 determination in natural water samples, with accuracy attested by HPLC-DAD.     

Preparation of a new benzylureido-β-cyclodextrin-based column and its application for the determination of phenylmercapturic acid and benzylmercapturic acid enantiomers in human urine by LC/MS/MS

Analytical and Bioanalytical Chemistry - A benzylureido-β-cyclodextrin was synthesized by the reaction of 6-amino-β-cyclodextrin with an active benzyl isocyanate. Then, it was bonded to...