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.