International Journal of Polymer Analysis and Characterization最新文献

In this article, various polyethylenes based on Ziegler-Natta and metallocene catalysts with different comonomer contents were investigated by successive self-nucleation and annealing (SSA) technique. Lamellar thickness, short chain branches content (SCBC) and methyl sequence lengths (MSL) were calculated by the modified Thomson-Gibbs equation and suitable calibration curves available in the literature. Moreover, linear low-density polyethylene (LLDPE) samples with different physical, mechanical and optical properties were investigated according to heat of fusion, the lamellar thickness, SCBC and methyl sequence length (MSL) of the multiple peaks. The results showed that the mechanical and optical properties such as dart drop impact strength, Elmendorf tear resistance, softening point and haze are associated with the lamellar thickness and SCBC of the resins.

The article presents the impedance analysis of polypyrrole (PPy)/La_0.7Ba_0.3MnO₃ (LBM) nanocomposites synthesized by in situ chemical oxidation method. The morphology and crystal structure were analyzed by Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) techniques. Vibration modes were analyzed using Fourier Transform Infrared spectroscopy (FTIR). The impedance behavior of the compounds was studied using an impedance analyzer in the frequency (100 Hz − 5 MHz) and temperature (30 °C − 90 °C) variation mode. Results of SEM and TEM for PPy, LBM, and PPy-LBM nanocomposites show spherical, rhombic and granular structures respectively. FTIR shows the presence of respective elements to be present for the formation of PPy, LBM, and PPy-LBM compounds. XRD patterns of PPy, LBM, and PPy-LBM nanocomposites show amorphous, orthorhombic, and semicrystalline phases respectively. The Real part of impedance shows decreasing value with frequency and the imaginary part of impedance shows the relaxing nature of the compounds. Cole − Cole analysis reveals the resistance contribution from grains and grain boundary. The equivalent circuit elucidated gives the combination of resistor and capacitor being parallel along with constant phase element and Warburg effects. The study helps us to understand the electric behavior of the samples whether capacitive or resistive type for which further studies can be conducted for sensor, anticorrosion coating, and spintronic applications.

Visible-light-driven azobenzene had been reported by theoretical calculation, but could not be detected by any characterization method due to unstable cis structure. Herein, copolymerization was applied to solve the problem based on a time-dependent characteristic of macromolecular motion. Therefore, two copolymers, namely, MRAA-PEG₂₀ copolymer and MRAA-NIPAM copolymer, were synthesized with a definite segment ratio. Both copolymers had photosensitive groups, which were confirmed by UV-vis spectra. Furthermore, copolymer concentration had a linear relationship with absorbance value at 425 nm. Firstly, blue light as an excitation source to induce the isomerization of copolymers. At the same time, repeated interval irradiation was used to evaluate the fatigue performance of the copolymer. Consequently, both copolymers could quickly transform to their cis isomers upon irradiation, which could be reversible recovered to their trans isomers in operable recovery time after removing irradiation. However, the MRAA-PEG₂₀ copolymer had an obvious photobleaching phenomenon along with the circle index, which did not exist in the MRAA-NIPAM copolymer. Secondly, the effects of excitation light source on isomerization were investigated. It was found that blue light was the most efficient excitation source for both copolymers though other light could also induce trans-to-cis transition. Thirdly, the influence of light intensity and temperature was respectively studied. With increasing of light intensity, the absorbance ratio before and after irradiation monotonously decreased, the irradiation response time shortened and the recovery response time prolonged. Moreover, higher temperature resulted in a higher absorbance ratio, shorter irradiation response time, and shorter recovery response time. Finally, synthesized copolymers had characteristic of pH indicator with a critical point of pH 5.0.

In this work, photoactive polymer film coatings were prepared using the breath figure (BF) method, starting from a poly(tert-butyl acrylate-styrene block), PtBA-block-PS and a photochromic agent, 1-(2-hydroxyethyl)-3,3-dimethylindoline-6-nitrobenzopyran (SP) grafted onto the poly(tert-butyl acrylate) block. The effects upon the composite film behavior in response to the solvent concentration, type of solvent and relative humidity were studied. Films containing homogeneously dispersed micrometre-sized pores were obtained. The optical and morphological behavior were investigated using optical microscopy and scanning electron microscopy. The films obtained have various potential applications as surface coating materials with color changing properties, such as whiteboards, device displays or advertising surfaces.

The properties of films prepared from polystyrene (PS), poly(methyl methacrylate) (PMMA), and polystyrene (PS)/poly(methyl methacrylate) (PMMA) blends and composite films prepared with metal ion-centered complexes were compared. New complexes of Cr(III), Co(II), Ni(II), and Cu(II) prepared according to the template were synthesized from ligand L (4-hydroxy-N-[2-[(4-hydroxybenzoyl)amino]ethyl]benzamide) prepared by condensation of 4-hydroxybenzoic acid and ethylenediamine. Structural analysis of ligands and complexes were determined by LC-MS, ¹H-NMR, FTIR, UV-Vis, and XRD. The conductivities and magnetic susceptibility of novel complexes were measured. Morphological properties of the transparent films by SEM and AFM, their thermal stabilities by TGA, and their optical properties by refractometry were characterized. Original composite films of PS, PMMA, and PS/PMMA blend modified with novel complexes were obtained as thermally stable, transparent, and foldable composite films with permanent colors.

Poly(ethylene oxide) has been intercalated inside the interlayer galleries of montmorillonite clay and the electrochemical properties of the nanocomposite have been investigated. Interlayer spacing and clay gallery width increase with increasing MMT concentration confirming intercalation of PEO into MMT as observed from XRD results. The fraction of free anions as calculated from FTIR, increases with increasing clay content and remains constant beyond 7.5 wt. % of clay content. Ionic conductivity of the order of 10⁻⁴ Scm⁻¹ has been obtained in the case of MMT based electrolytes. The initial increase of conductivity with increasing MMT content can be attributed to the increase fraction of free ions which eventually increases ionic conductivity. After 7.5 wt. % of MMT loading ionic conductivity decreases due to the high viscosity of MMT. Interfacial stability results show that passivation takes place very slowly in MMT based electrolytes. Dielectric properties show that at high frequency relaxation takes place due to the segmental motion of polymer chains and it proves the hopping of ions.

Astronauts suffer from natural space radiation as high-energetic protons, heavy ions, and secondary particles produced in collisions. Galactic cosmic rays and solar particle events are the basic parts of space radiation spectra. Wears and accessories designs for use by astronauts aim to minimize these deleterious effects of this environment. Polymeric materials are preferred in astronaut suits because they are lightweight, inexpensive, and durable. Teflon, KEVLAR, ethylene tetrafluoroethylene, DYNEEMA, and NOMEX polymeric astronaut wear materials were exposed to high energetic proton irradiations by the use of Monte Carlo simulation tools SRIM-2013 and FLUKA 2011.1. Proton energies are applied as 1, 2, and 3 GeV known as in order of space radiation magnitude. Besides, displacement per atom calculations were done and results were discussed in the plane of structural changes in the given polymeric materials. After interacting with protons with 1, 2, and 3 GeV energies, the material with the lowest Displacement per atom value among the five studied materials is DYNEEMA with values of 1.01E − 25, 9.96E − 26, and 1.00E − 25, respectively. Again, among the materials studied for these three proton energies, DYNEEMA has the highest electronic stopping power values are, respectively, 2.11E − 03, 2.10E − 03, and 2.31E − 03. DYNEEMA has the highest nuclear stopping power values as 2.23E − 07, 1.53E − 07, and 4.27E − 07, respectively.

In the present work we are aimed to use powerful and state of the art methodology to optimize catalyst synthesis procedure. In this way, the preparation process of supported Ziegler–Natta catalysts was simulated and optimized through artificial intelligence (AI) methodology coupled with genetic algorithm (GA). The yield of preparation process was investigated through assessing the catalyst activity. The effects of several variables including TiCl₄ injection temperature, TiCl₄/toluene ratio, and TiCl₄ injection time on the activity of prepared catalyst were investigated. In model development, leave-one-out technique was used for training the network. The developed neural network model can be utilized to enhance the efficiency of the catalyst preparation process.

A novel nanocomposite consisting of polyurethane (PU), poly(o-phenylenediamine) (PoPD), and silicon carbide (SiC) nanoparticles was investigated for its application in marine environment through electrochemical techniques. The PoPD/SiC nanofillers were characterized by TGA, XRD, SEM/EDX, and TEM analyses. The anticorrosion and mechanical properties of different coating formulation in marine environment were evaluated by electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM). It was also found that the coating resistance of PU-PoPD/SiC nanocomposite was over 41 times higher than that of the PU coating. The PU-PoPD/SiC coatings on the brass showed low current of 1.9 I/nA due to copper dissolution and 6.8 I/nA due to zinc dissolution because of the well distribution of PoPD/SiC nanofiller in PU coating. The analyses of the resultant degradation products by SEM/EDX and XRD techniques confirmed the presence of Si which has a major role in protecting the brass surface against corrosion. Results showed that the PU composite with 2 wt.% PoPD/SiC hybrid nanofillers had outstanding coating performance. This nanocomposite demonstrated improved corrosion protection. As a result, the developed PU-PoPD/SiC nanocomposite has exceptional adhesion strength and anticorrosion properties and might be exploited to develop next-generation anticorrosive coatings.

The demand for stretchable, skin-mountable, and wearable strain sensors is burgeoning because they are required for several budding applications in various emerging fields, such as health monitoring, human-machine interfaces, wearable electronics, soft robotics, human motion detection, virtual reality (VR), and so forth. Recently, strain sensors based on composite materials comprising stretchable elastomer and conductive nano-filler have gathered attention on account of their ample flexibility, record stretchability, excellent durability, customizable characteristics for strain-sensing, and simpler fabrication techniques. This quality write-up discusses current developments in the field of flexible strain sensors (FSSs). We effectively summarized how advanced mechanisms, such as crack propagation, disconnection, and tunneling effect, which are quite different from traditional strain sensing techniques, are used to develop FSS. Various factors and their effects that need to be kept in mind while developing high-performance, high-quality FSSs are also debated. The performance of recently reported FSSs is comprehensively discussed, and the huge potential that FSSs hold has been comprehensively reviewed in this survey.