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This paper focuses on designing and investigating a new type of metamaterial called an ultra-thin wide-band mu-negative (MNG) metamaterial. The targeted frequency range is 0.1–10 THz. At the resonance frequency of 6.37 THz, the permeability (μ) of the structure is negative, allowing it to function as an MNG metamaterial. Computer Simulation Technology (CST) and High-Frequency Structure Simulator (HFSS) 3D software simulations, examining the scattering and medium parameters of the MNG metamaterial. The findings demonstrate that the proposed MNG metamaterial exhibits resonance peaks in the mu-negative region at 6.37 THz and wide frequency bands of 8.79 THz at −10 dB in the CST simulator. The structure is adaptable based on design parameters. This MNG metamaterial is unique due to its ultra-thin, a form mu-negative wide bandwidth of 3.20 THz, and suitable resonance frequencies. The simulation results from Ansys HFSS software almost align with CST results. The structure, resonating in the THz region with wide bandwidth, shows potential applications in spectroscopy and biomedical engineering. The study encountered difficulties in achieving precise fabrication at the nanoscale and ensuring the reproducibility of metamaterial properties across various samples. Despite these challenges, the proposed metamaterial shows significant advancements in terahertz technology.

Although stimuli-responsive polymers have appeared as promising materials for drug administration, the effectiveness of these materials on various bioinspired stimuli is still open for dispute. In this work, the stimuli-responsive behaviors of radical-containing nonamphiphilic copolymers were investigated using electron paramagnetic resonance (EPR) spectroscopy while altering the pH and reductant concentration. The concentration of radicals in the aqueous solution had a considerable impact on self-assembly. The nitroxide radicals (hydrophobic) were converted to hydroxylamine (hydrophilic) when ascorbic acid (Asc) was added as a reductant, and the assemblies were switched to dissolution with a rate control behavior. The behavior of morphological change was observed in the acidic pH due to the disproportionation reaction of nitroxide radicals forming cationic species. The acquired results give new insights into the colloidal nanoparticles of nonamphiphilic copolymers and encourage the development of comparable responsive nanoparticles with intriguing drug delivery applications.

Study of the segmental mobility of polymer chains is important when the polymer is used as drag reduction agents of crude oil. Electron spin resonance (ESR) spectroscopy can provide important information about segmental dynamics of polymer chains, which is related to their microenvironment. In this article, we employed an amphiphilic polymer to study the effect of hydrophilic/hydrophobic balance of the polymers on the segmental motion of polymer chains. Poly(styrene-co-maleic acid) (PSMA) was spin labeled with 4-amino TEMPO radicals by increasing the concentration of radical moiety on the polymer chains. The PSMA and spin labeled-PSMAs (SL-PSMAs) were characterized by nuclear magnetic resonance (NMR), Fourier transform infrared (FT-IR) spectroscopy, Cyclic voltammetry (CV) and ESR techniques. Inter-polymer complexes (IPCs) of SL-PSMA-2 were prepared by employing polyethylene glycols (PEGs) of varying molecular weights. The results showed that the increased hydrophobic interactions of nitroxide radicals on the SL-PSMAs’ chains reduced the rotational mobility of spin labels and the random coil-to-globular transition of polymer chains occurred at higher pH value for SL-PSMAs, which showed a slow motion component in the ESR spectra of SL-PSMAs. Further, by increasing the molecular weight of PEGs in IPCs the complexation was increased, which also reduced the rotational motion of spin labels due to interpolymer hydrogen bonding causing a slow motion component in the ESR spectra.

The structure of polyolefin has an important influence on its performance and application. Ethylene/1-hexene copolymerization is one of the important ways to control the structure of the polyolefin. However, research on the ethylene/1-hexene copolymerization catalyzed by nickel complexes with different steric ligands remains to be refined. Here, three α-diimine nickel catalysts are used to study the ligand effect on catalytic performance in the ethylene/1-hexene copolymerization. Reaction activity, molecular weight, phase-transition temperature and branching density of the resultant copolymer are measured to evaluate the catalytic performance. The results indicate that the steric ligands could exert great effect on the copolymerization. As for the chemical valence of Ni species, detailed EPR demonstrate that the presence of excess co-catalyst can reduce Ni(II) to the lower valence and affect the catalytic performance.