Hydrogen Bonding Interactions in Miscible Blends of Poly(hydroxyether ester)s with Poly(N‐vinyl pyrrolidone)

Studies on the miscibility and intermolecular specific interactions in the blends of two structurally similar poly(hydroxyether ester)s, poly(hydroxyether terephthalate ester) (PHETE), and poly(hydroxyether benzoate) (PHEB) with poly(4‐vinyl pyrrolidone) (PVPy) are reported. In the miscible blends there are intermolecular specific interactions between PHEEs and PVPy. It was found that intercomponent hydrogen‐bonding interactions in PHETE/PVPy blends are much stronger than those in PHEB/PVPy blends. It seems that the higher ratio of hydroxyl to carbonyl groups results in the stronger intermolecular hydrogen bonding interactions. The difference in intermolecular specific interactions between the two miscible systems is interpreted on the basis of the impact of macromolecular structures on intermolecular specific interactions. The structural characteristics of macromolecular chains, such as chain connectivity, accessibility (or screening effect), and rigidity of the macromolecular chains have a profound effect on the intermolecular interactions. These factors constitute steric hindrance and reduce the specific interactions among functional groups. These factors can become dominant in the blends of polymers.     

Preliminary studies on LED-activated pyropheophorbide-α methyl ester killing cisplatin-resistant ovarian carcinoma cells

In the present study, a novel LED source was applied for activating pyropheophorbids-a methyl ester (MPPa) in cisplatin-resistant ovarian cell line COC1/DDP cells. MPPa concentration was 2 μM and light energy from 0.125–8 J/cm². Cytotoxicity was investigated 24 h using MTT reduction assay and light microscopy after treatment. Cellular ultrastructure was observed using transmission electron microscopy (TEM) and nuclear chromatin by fluorescent microscope with Hoechst33258 staining. MTT reduction assay showed that the cytotoxicity of LED-activated MPPa in the COC1/DDP cells increased along with the light dose of LED source and LED-activated MPPa resulted in light-dependent cytotoxicity. The observations from light microscopy reinforced the above results. TEM showed that necrotic cells with the disruption of karyotheca, karyorrhexis, and karyolysis of nucleus and apoptotic cells, especially the apoptotic body, can be seen post LED-activated MPPa. Hoechst33258 staining showed that condensation of chromatin and nuclear fragmentations could be found in many treated cells and some of them formed the structure of apoptotic bodies when COC1/DDP cells were exposed to 2 μM MPPa for 20 h and then 1 J/cm² irradiation of LED source. The findings demonstrated that the novel LED source could efficiently activated MPPa and LED-activated MPPa could significantly kill cisplatin-resistant ovarian cell line COC1/DDP cells through two major pathways including necrosis and apoptosis, suggesting that LED is a novel and efficient light source and LED-activated MPPa might be potential therapeutic modality for treating cisplatin-resistant ovarian carcinoma.     

Synthesis,characterization and mesomorphic properties of new liquid-crystalline compounds involving ester–chalcone linkages

We report the synthesis and evaluation of thermal behaviour of two novel series of chalcone-based liquid-crystalline compounds. The flexibility in these systems is provided by attaching straight alkoxy chain at one end. All the mesogens have been characterized by spectroscopic methods such as ¹H-NMR, FTIR, mass spectra, UV/Vis, and also elemental analysis. Their thermal behaviour was evaluated mainly by polarizing optical microscopic observation and DSC studies. It has been observed that the majority of the compounds display nematic and/or smectic mesophases. In both the series, compounds having C₃ to C₇ tail display only enantiotropic nematic phase, whereas C₈ and C₁₀ homologues exhibit enantiotropic smectic C and nematic phases. The higher homologues with C₁₂, C₁₄ and C₁₆ tails show the smectic C phase only.     

Laser infrared spectroscopy of vinyl fluoride in the 1280–1400 cm−1 region

The infrared spectra of CH₂=CHF have been investigated in the ν₅ and ν₆ band regions between 1280 and 1400?cm^?1, at a resolution of about 0.002?cm^?1, using a tunable diode laser spectrometer. These vibrations of symmetry species A′ give rise to a/b-hybrid bands with different contributions from both the components. Spectral analysis resulted in the identification of 1565 (J≤46, K _a ≤11) and 1651 (J≤48, K _a ≤15) transitions of the ν₅ and ν₆ fundamentals, respectively. Both bands are perturbed by the nearby states ν₈?+?ν₉ and ν₉?+?ν₁₁ through different Coriolis resonances and an anharmonic interaction. Using Watson's A-reduction Hamiltonian in the I^r representation and perturbation operators almost all the transitions have been fitted simultaneously to a model including six resonances within the tetrad ν₅/ν₆/ν₈?+?ν₉/ν₉?+?ν₁₁. A set of spectroscopic constants for the ν₅ and ν₆ bands, as well as parameters for the dark states ν₈?+?ν₉ and ν₉?+?ν₁₁ and coupling constants, have been determined. From spectral simulations the dipole moment ratio |Δμ _a /Δμ _b | was estimated to be 0.6?±?0.1 and 2.0±0.3 for the ν₅ and ν₆ bands, respectively.     

A Study on Properties of Poly(vinyl chloride)/Poly(α-methylstyrene-acrylonitrile) Binary Blends

Blends of poly(vinyl chloride) (PVC) and poly(α-methylstyrene-acrylonitrile) (α-MSAN) with variable composition of 0 to 100 wt% were prepared by melt mixing. Properties of binary blends were extensively studied by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), heat distortion temperature (HDT), mechanical properties, melt flow rate (MFR), and scanning electron microscope (SEM). A single glass transition temperature (T_g ) was observed by DSC and DMTA, indicating miscibility between PVC and α-MSAN. The results of ATR-FTIR indicated that specific strong interactions were not present in the blends and the miscibility was due to interaction between –CN and PVC. With increasing amount of α-MSAN, considerable increase occurred in HDT, flexural strength, and flexural modulus compared with reverse s-shaped decrease in impact strength and elongation at break. Synergism was observed in tensile strength and MFR. No phase separation was observed in SEM photographs, indicating miscibility between PVC and α-MSAN. In addition, morphology of the impact-fractured surfaces, including roughness and non-fused particles, correlated well with the mechanical properties and MFR.     

Ferroelectric and phase transition studies in cesium nitrate: poly(vinyl?alcohol)?composite films

The composite films of cesium nitrate (CsNO₃) and poly(vinyl alcohol) (PVA) with varying composition were prepared using the solvent cast method. The hysteresis loop characteristics show optimum remnant polarization (P _r ) of 2.75 μC/cm² at 50 wt.% composition. The field emission scanning electron microscope images show a nearly homogeneous distribution of CsNO₃ grains in the 50 wt.% composite film. The temperature dependence of the remnant polarization shows a diffused transition temperature range from the ferroelectric to the paraelectric phase and this has been attributed to the reduced enthalpy. The butterfly features of the dielectric constant–voltage (ε–V) characteristics have been attributed to polarization switching.     

Vapor–liquid and liquid–liquid equilibrium for binary systems ester + a new protic ionic liquid

This study reports the synthesis of a new protic ionic liquid, bis(2-hydroxyethyl)ammonium butyrate (2-HE₂AB), performed by a Brønsted acid–base reaction between butanoic acid and bis(2-hydroxyethyl)ammonia. The new ionic liquid was characterized by 1D hydrogen NMR spectrum. The ionic liquid shows complete solubility in water, methanol, and ethanol, and is partially soluble in methyl acetate, ethyl acetate, and propyl acetate, while it is not soluble in some alkanes. Density, refractive index, and vapor–liquid equilibrium were measured for the binary system 2-HE₂AB + methyl acetate at atmospheric pressure. Furthermore, density, refractive index, and liquid–liquid equilibrium were measured for the binary systems 2-HE₂AB + ester (methyl acetate, ethyl acetate, or propyl acetate) at 293.2 K. The Peng-Robinson equation of state, coupled with the Wong-Sandler mixing rule, was used in the thermodynamic modeling of density, vapor–liquid, and liquid–liquid equilibrium data. The COSMO-SAC activity coefficient model was used to calculate the activity coefficient within the Wong-Sandler mixing rule. The calculations show deviations for density, for the vapor–liquid equilibrium, and for the non-polar and polar phases of the liquid–liquid equilibrium within 13.0, 0.1, 132.5, and 23.8 %, respectively.     

Comparative study on ethyl butanoate reactivity – Experimental investigation and kinetic modeling of the C6 ethyl ester

Ethyl butanoate is a representative for oxygenated hydrocarbons as they are discussed as future liquid fuels from sustainable production pathways. An in-depth understanding of the influence of oxygen on the reactivity of those fuel candidates is mandatory for the molecular design and their application in internal combustion engines. Towards this goal, ignition delay times for ethyl butanoate were measured at conditions relevant to internal combustion engines using a shock tube and a rapid compression machine. These experiments were conducted for stoichiometric mixtures with air-like conditions at pressures of 20, 30 and 40 bar and a total temperature range of 680–1260 K. A negative temperature coefficient regime was found where the ignition delay times increased with increasing temperatures for all covered pressures. To further understand the kinetics of ethyl butanoate and the influence of the ester functional group, a detailed kinetic mechanism was developed and validated against the measured ignition delay times. A good agreement between the measured data and the prediction by the newly developed mechanism was achieved. The findings of this work were then used to compare ethyl butanoate to di-ethyl carbonate, methyl pentanoate and n-heptane, which also show a seven-heavy-atom-membered main chain and have all been kinetically studied before. The differences between the molecular structures and their effect on the kinetic pathways was discussed to extract information for future fuel design. It was found that especially the inhibting effect of oxgen atoms on six-membered internal H-atom migration reactions has a significant impact on the fuel’s reactivity.     

Poly(acrylamide‐co‐acrylic acid)/Poly(vinyl pyrrolidone) Polymer Blends Prepared by Dispersion Polymerization

The structure and properties of a three‐component system, a poly(acrylamide‐co‐acrylic acid)/poly(vinyl pyrrolidone) [P(AM‐co‐AA)/PVP] polymer blend prepared by dispersion polymerization, were studied. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed that the resulting P(AM‐co‐AA) microspheres with diameters between 200–300 nm were well‐dispersed in the PVP matrix. Fourier transform infrared spectra (FTIR) showed that intermolecular hydrogen bonding interaction occurred between the dispersed phase and the continuous phase. The mechanical properties of P(AM‐co‐AA)/PVP polymer blends were also determined. With different mass ratios of acrylamide to acrylic acid, it was found that the blends had better mechanical properties with increased AA content.     

Apatite formation on Poly (vinyl alcohol)-coated Poly (?-caprolactone) films by incubation in simulated body fluids

In this study, biodegradable poly (?-caprolactone) (PCL) films were coated with poly (vinyl alcohol) (PVA) and then incubated in a simulated body fluid 1.5SBF to prepare an apatite (HA)/PCL composite. It was found that the bone-like apatite formability of PCL was enhanced by PVA coating. The changes of surface properties induced by PVA coating were effective for apatite formation. The apatite formability increased with increasing coating amount. After 24 h incubation, apatite was formed on PVA-coated PCL film but hardly any apatite was found on uncoated PCL plate. The surface chemistry of the specimens was examined using XPS, FT-IR-ATR. The apatite formed was characterized by using SEM, TF-XRD, FT-IR, EDS. The apatite formed was similar in morphology and composition to that of natural bone. This indicated that simple PVA coating on PCL substrate could serve as a novel way to accelerated apatite formation via biomimetic method.     

Effect of dibutyl phthalate as plasticizer on high-molecular weight poly(vinyl chloride)–lithium tetraborate-based solid polymer electrolytes

A series of different composition of polymer electrolytes-based on poly(vinyl chloride) (PVC) as host polymer, lithium tetraborate (Li₂B₄O₇) as dopant salt, and dibutyl phthalate (DBP) as plasticizer were prepared by solution casting method. The interaction between the PVC, Li₂B₄O₇, and DBP were studied by Fourier transform infrared. The shifting, broadening, and splitting of transmission peaks were the evidences of complexation. The highest ionic conductivity polymer electrolyte of 2.83 × 10⁻⁶ S/cm was achieved at ambient temperature upon addition of 30 wt.% of DBP. In addition, the temperature-dependent conductivity, frequency-dependent conductivity, dielectric permittivity, and modulus studies were performed. The temperature-dependent conductivity of the polymer electrolytes was found to obey the Arrhenius behavior. The thermal stability of polymer electrolytes was verified by thermogravimetric analysis. The lower in glass transition temperature was proven in differential scanning calorimetry, whereas the higher amorphous region within the polymer matrix was demonstrated in X-ray diffraction.     

Acoustic behaviour and equation of state of amorphous ethylene–vinyl acetate copolymer studied by means of high-pressure Brillouin scattering spectroscopy

The determination of the equation of state (EOS) of amorphous materials is very important for fundamental understanding of the glass transition and applications as well. Simultaneous observation of both longitudinal and transverse acoustic modes by Brillouin scattering spectroscopy has been one of the major methods to obtain EOS of amorphous materials. However, the transverse acoustic mode is hardly seen from some of the amorphous polymers, which makes it difficult to derive EOS. The temperature and pressure dependences of the acoustic properties of amorphous ethylene–vinyl acetate (EVA) copolymer were measured by using high-pressure Brillouin scattering spectroscopy. The temperature variation induced large changes in the frequency shift and linewidth of the longitudinal acoustic mode due to strong coupling between the structural relaxation process and the propagating density fluctuations. The residual linewidth in the glassy state was attributed to the remnant intramolecular motions of EVA, the activation energy of which was estimated to be ～3.30 ± 0.27 kcal/mol. The pressure–density relationship of EVA could be obtained for the first time by measuring the refractive index and using the Lorentz–Lorenz equation. The density and the refractive index exhibited monotonic increase up to approximately 12 GPa. The strong reduction of the acoustic damping at low pressures below ～3 GPa was attributed to the collapsing free volume in EVA. The present study clearly shows that measuring the refractive index by high-pressure Brillouin spectroscopy may be an alternative method to get the EOS of polymeric materials whose transverse acoustic mode is too weak to be observed.     

Preparation of poly(vinyl alcohol)–silicone based hybrid membranes for the pervaporation separation of water–acetic acid mixtures

Hybrid membranes were prepared using poly(vinyl alcohol) (PVA) and tetraethylorthosilicate (TEOS) via hydrolysis followed by condensation. The obtained membranes were characterized by Fourier transform infrared spectroscopy, wide-angle x-ray diffraction and differential scanning calorimetry. A remarkable decrease in degree of swelling was observed with increasing TEOS content in membranes and is attributed to the formation of hydrogen bonding and covalent bonds in the membrane matrix. The pervaporation performance of these membranes for the separation of water–acetic acid mixtures was investigated in terms of feed concentration and the content of TEOS used as cross-linking agent. The membrane containing 1 : 2 mass ratio of PVA and TEOS gave the highest separation selectivity of 1116 with a flux of 3.33 × 10^?2kg/m²h at 30°C for 10 mass% of water in the feed. Except for membrane M-1, the observed values of water flux are close to the values of total flux in the investigated composition range, signifying that the developed membranes are highly water selective. From the temperature dependence of diffusion and permeation values, the Arrhenius apparent activation parameters have been estimated. The resulting activation energy values obtained, showing that water permeation is lower than that of acetic acid, suggest that the membranes have higher separation efficiency. The activation energy values calculated for total permeation and water permeation are close to each other for all the membranes except membrane M-1, signifying that coupled-transport is minimal because of the higher selective nature of membranes. The negative heat of sorption values (ΔH _s) for water in all the membranes suggests a Langmuir mode of sorption.     

Structural,thermal and electrical properties of polyvinyl alcohol/poly(vinyl pyrrolidone)–sodium nitrate solid polymer blend electrolyte

Sodium ion conducting solid polymer blend electrolyte thin films have been prepared by using polyvinyl alcohol (PVA)/poly(vinyl pyrrolidone) (PVP) with NaNO₃ by solution cast technique. The prepared films were characterized by various methods. The complexation of the salt with the polymer blend was identified by X-ray diffraction (XRD) and Fourier transforms infrared spectroscopy (FTIR), Differential scanning calorimetry was used to analyze the thermal behavior of the samples, and the glass transition temperature is low for the highest conducting polymer material. The scanning electron microscopy gives the surface morphology of the polymer electrolytes. The frequency and temperature dependent of electrical conductivities of the films were studied using impedance analyzer in the frequency range of 1 Hz to 1 MHz. The highest electrical conductivity of 50PVA/50PVP/2 wt% NaNO₃ concentration has been found to be 1.25 × 10^?5 S cm^?1 at room temperature. The electrical permittivity of the polymer films have been studied for various temperatures. The transference number measurements showed that the charge transport is mainly due to ions than electrons. Using this highest conducting polymer electrolyte, an electrochemical cell is fabricated and the parameters of the cells are tabulated.     

Dielectric Dispersion Study of Poly(vinyl Pyrrolidone)–Polar Solvent Solutions in the Frequency Range 20 Hz–1 MHz

Influence of polar solvents environment and polymer concentrations on the electrical properties (complex dielectric constant, ac electrical conductivity, complex electric modulus and complex impedance) of the solutions of poly(vinyl pyrrolidone) (PVP) in polar solvents, namely water, ethyl alcohol, ethylene glycol, diethylene glycol, poly(ethylene glycol), glycerol, dimethyl sulfoxide and dimethyl formamide, have been investigated in the frequency range 20 Hz–1 MHz at 25°C. Comparative analysis of the dielectric dispersion curves confirms that the solvent molecular size and number of its hydroxyl groups, and the solutions viscosity, are the major factors which governs the PVP chain segmental motion. The ionic conduction and electrode polarization phenomena has a dominant influence on the large increase of complex dielectric constant values of the solutions of PVP‐polar solvent in the lower frequency region. The values of relaxation times corresponding to these phenomena are also reported.     

Radiation damage produced in powder of α-(methylamino)isobutyric acid, α -aminoisobutyric acid methyl ester hydrochloride and diethylmalonic acid

The electron paramagnetic resonance spectra of γ-irradiated powders of α-(methylamino)isobutyric acid – CH₃NHC(CH₃)₂COOH, α -aminoisobutyric acid methyl ester hydrochloride – NH₂(CH₃)₂CCOOCH₃ HCl, and diethylmalonic acid – (CH₃CH₂)₂C(COOH)₂ have been investigated at room temperature. It has been found that γ -irradiation produces the (CH₃)₂C˙COOH radical in the first, the (CH₃)₂C˙COOCH₃ radical in the second and the (CH₃CH₂)₂C˙COOH radical in the third compound. The spectra were computer-simulated. The g values and the hyperfine coupling constants of the unpaired electron with the environmental methyl, methylene protons and OH proton were determined. The results were found to be in good agreement with the existing literature data and theoretical predictions.     

Examination of wavelength dependent soot optical properties of diesel and diesel/rapeseed methyl ester mixture by extinction spectra analysis and LII measurements

The refractive index of soot is an essential parameter for its optical diagnostics. It is necessary for quantitative interpretation of LII (Laser Induced Incandescence) signals, light scattering or extinction measurements as well as for emissivity calculations. The most cited values have been determined by intrusive methods or without taking into account the soot size distribution and its specific morphology. In the present study, soot generated by the combustion of diesel and diesel/rapeseed methyl ester (RME) mixture (70% diesel and 30% RME) are extensively characterized by taking into account the morphology, the aggregate size distribution, the mass fraction and the spectral dispersion of light. The refractive index m for wavelengths λ between 300 and 1000 nm is determined for diesel and diester fuels by both in-situ and ex-situ methods. The ex-situ method is based on the interpretation of extinction spectra by taking into account soot sizes and fractal morphology with the RDG-FA (Rayleigh–Debye–Gans for Fractal Aggregate) theory. The in-situ approach is based on the comparison of the LII signals obtained with two different excitation wavelengths. The absorption function E(m) and the scattering function F(m) are examined. This study reveals similar optical properties of soot particles generated by both studied fuels even at ambient and flame temperatures. The function E(m) is shown to reach a maximum for λ=250 nm and to tend toward a plateau-like behavior close to E(m)=0.3 for higher wavelength (600<λ (nm)<1000). The function F(m) is found to be quite constant for 400<λ (nm)<1000 and equal to 0.31.     

Preparation and Evaluation of the Morphology,Flammability, and Mechanical Properties of the Acrylonitrile‐Butadiene‐Styrene/Poly (vinyl chloride) Blends

Blends of two grades of acrylonitrile‐butadiene‐styrene (ABS) with three different compounds of poly (vinyl chloride) (PVC) were prepared via melt processing and their morphology, flammability, and physical and mechanical properties were investigated. SEM results showed that the ABS/PVC blend is a compatible system. Also, it can be inferred from fracture surface images that ABS/PVC blends are tough, even at low temperatures. It was found that properties of these blends significantly depend on blend composition and PVC compound type; however, the ABS types have only a small effect on blend properties. On blending of ABS with a soft PVC compound, impact strength, and melt flow index (MFI) increased, but tensile and flexural strength decreased. In contrast, blending of ABS with a rigid PVC compound improved fire retardancy and some mechanical properties and decreased MFI and impact strength.