Synthesis, characterization, and acoustic properties of new soluble polyurethanes based on 2,2′-[1,4-phenylenebis(nitrilomethylylidene)diphenol and 2,2′-[4,4′-methylene-di-2-methylphenylene-1,1′-bis(nitrilomethylylidene)]diphenol

Improvement in Migration Resistance of Hydroxyl-Terminated Polybutadiene (HTPB) Liners by Using Graphene Barriers

The excessive migration of plasticizers leads to debonding and cracking of a liner, which can compromise the safety of a solid propellant. Graphene oxide (GO), with a laminar structure as a filler, can effectively reduce the migration of plasticizers. In this study, we modified GO using toluene diisocyanate (TDI). The cross-link density of the substrate was increased by grafting isocyanate groups to obtain a denser liner for the purpose of preventing plasticizer migration. We also used octadecylamine (ODA) to modify GO by grafting negatively charged amide groups on the GO surface. The electrostatic repulsive effect of the amide group on the plasticizer molecules was used to prevent plasticizer migration. Two modified GOs were filled into the hydroxyl-terminated polybutadiene to prepare two composite liners. We then investigated the migration resistance and migration kinetics of each modified liner using the dipping method. In addition, we explored the mechanical properties of each modified liner. Compared with the original liner, the anti-migration and mechanical properties of the modified composite liners were significantly improved. Among them, the TDI-modified liner had the most obvious improvement in migration resistance, while the ODA-modified liner had the greatest improvement in bonding properties. All types of liners met the requirements of the current propellant systems. This study provides an effective reference for improving the migration resistance and bonding properties of the composite liner.

Effects on the crystallization behavior and biocompatibility of poly(LLA-ran-PDO-ran-GA) with poly(d-lactide) as nucleating agents

The blends of poly(l-lactide acid-p-dioxanone-glycolide) (PLPG) with poly(d-lactide) (PDLA) (PLPG/PDLA) were prepared by a solution-casting method. The effects of PDLA on the properties of the PLPG were studied. DSC and WAXD results confirmed that PLA stereocomplex (sc-PLA) crystals were formed by blending PLLA segments in PLPG with PDLA, and the melting endotherm for both PLLA and sc-PLA relied on PDLA content. The non-isothermal crystallization results indicated that the crystallization process was remarkably accelerated by the addition of PDLA. Meanwhile, the results of isothermal crystallization indicated that the half-time of crystallization decreased with the increase of PDLA content. Besides, the enzymatic degradation behavior of the samples showed that with the increase of PDLA content, the mass loss gradually decreased. Furthermore, TGA and DTG results indicated that the thermal degradation of the samples was a complex process. Moreover, the biocompatibility of the samples was tested by cell culture and using CCK-8 and live/dead staining. Results showed that the samples possessed lower cytotoxicity. Therefore, the PLPG/PDLA blends are promising candidate materials in biomedical applications.

Sc-PLA crystals in the PLPG/PDLA blends were formed by hydrogen bond between PDLA and PLLA segments, which enhance the crystallization ability of PLLA in the PLPG matrix by decreasing the activation free energy.

Rapid, ultrasensitive, highly selective detection of toxic Hg(II) ions in seabass, swordfish and water samples

A novel fluorescent probe bearing triphenylamine, thiophene and thiosemicarbazide (TPA-TSC) was developed, and its distinct features were investigated. TPA-TSC demonstrated excellent selectivity towards Hg²⁺ ions, with a limit of detection (0.14 nM) among the lowest reported to date. It also exhibited a turn-off response by forming stable complex for a brief period (<30 s). Job plot analysis and high-resolution mass spectrometry (HRMS) revealed that TPA-TSC bound to Hg²⁺ with a 2:1 stoichiometry in an aqueous environment, remarkably the probe successfully detected Hg²⁺ ions in seabass, swordfish and different samples of water. In all, TPA-TSC offers a promising method for accurately determining the quality of seafood and water samples polluted with Hg²⁺.

Synthesis of calixresorcarenes using magnetic poly triazine-benzene sulfonamide-SO3H

The purpose of this work is to develop a magnetically recyclable immobilized base catalyst for the green synthesis of calixresorcarenes. To achieve this, poly triazine-benzene sulfonamide (PTBSA) has been coated on magnetic Fe₃O₄ nanoparticles and subsequently chlorosulfonic acid has been supported to obtain Fe₃O₄@PTBSA-SO₃H. The structure of nano-Fe₃O₄@PTBSA-SO₃H was characterized by TEM, XRD, FT-IR, VSM, WDX, EDX, TGA/DSC and FE-SEM. The catalytic efficiency of this catalyst was also investigated in the synthesis of novel calixresorcarene derivatives. The advantages of heterogeneous nature, catalytic activity and the recyclability of the polymer support were also strengthened by advanced surface treatment. These key factors (basic sites, acidic sites and heterogeneity) play essential roles in the catalyst performance. This procedure has some advantages such as short reaction time, clean and fast work-up and easy separation of the catalyst by an external magnet.

Magnetic poly triazine-benzene sulfonamide-SO₃H was investigated for the synthesis of calixresorcarenes.

meta-Terphenyl linked donor–π–acceptor dyads: intramolecular charge transfer controlled by electron acceptor group tuning

A series of meta-terphenyl linked donor–π–acceptor (D–π–A) dyads were prepared to understand the electronic effects of a meta-terphenyl linker according to the electron-accepting ability change. The energy band gaps of the dyads were controlled by tuning the accepting ability, which resulted in emission colors ranging from blue-green to red. In the Lippert–Mataga plots, intramolecular charge transfer (ICT) behavior was observed, which showed gradually increased ICT characteristics as the accepting ability was increased. On the other hand, in the absorption spectra, a red shift of the ICT transition was observed differently from the electron-accepting ability tendency. Thus, the experimental results show that the ICT is determined by steric hindrance rather than the acceptor ability in the ground state due to the lack of π-conjugation of the terphenyl linker by the electron node in the meta-position, whereas ICT in the excited state is controlled by electron-accepting ability.

Dyads were prepared to understand the electronic effects of a meta-terphenyl linker according to the accepting ability change. The charge transfer properties in the ground/excited state are determined by accepting ability and/or steric hindrance.

Membrane Surface Engineering with Bifunctional Zwitterions for Efficient Oil-Water Separation

Chemical modification provides a solution to the membrane fouling problem in oily water purification. However, complicated synthesis processes and harsh reaction conditions are frequently encountered with this approach. Here we developed two bifunctional zwitterionic materials, i.e., n-aminoethyl piperazine propanesulfonate (P-SO₃-NH₂) and 1,4-bis (3-aminopropyl) piperazine propanesulfonate (P-2SO₃-2NH₂), by a clean method and grafted them onto membrane surface via a fast single-step reaction. These materials endow the resultant membrane a more hydrophilic and smoother surface, significantly improving the water permeability, fouling resistance and recyclability of membrane in forward osmosis oily water reclamation. The water fluxes produced by the P-2SO₃-2NH₂ modified membrane are 47% (from 20.0 to 29.3 LMH) and 60% (from 16.0 to 25.6 LMH) higher than those of the unmodified membrane when DI water and an oily emulsion (1500 ppm) as the respective feeds. A higher water flux recovery is also achieved for the P-2SO₃-2NH₂ modified membrane (94%) than that of the nascent membrane (82%) after a 12-h experiment. These promising findings coupled with a facile and efficient membrane modification approach provide inspiration for both membrane exploration and oily water treatment.

Facile immobilization of glucose oxidase onto gold nanostars with enhanced binding affinity and optimal function

Gold nanoparticles provide a user-friendly and efficient surface for immobilization of enzymes and proteins. In this paper, we present a novel approach for enzyme bioconjugation to gold nanostars (AuNSs). AuNSs were modified with l-cysteine (Cys) and covalently bound to N-hydroxysulfosuccinimide (sulfo-NHS) activated intermediate glucose oxidase (GOx) to fabricate a stable and sensitive AuNSs-Cys-GOx bioconjugate complex. Such a strategy has the potential for increased attachment affinity without protein adsorption onto the AuNSs surface. Good dispersity in buffer suspension was observed, as well as stability in high ionic environments. Using the AuNSs-Cys-GOx bioconjugates showed greater sensitivity in the measuring of low concentrations of glucose based on plasmonic and colorimetric detection. Such a novel approach for enzyme immobilization can lead to AuNSs-Cys-GOx bioconjugate complexes that can be used as catalytic nanodevices in nanobiosensors based on oxidases in biomedical applications.

Modulation of aggregation with an electric field; scientific roadmap for a potential non-invasive therapy against tauopathies

Toxic aggregation of tau protein to neurofibrillary tangles (NFTS) is a central pathological event involved in tauopathies. Inhibition of tau protein aggregation can serve as a straightforward therapeutic strategy. However, tau-based therapeutic solutions are not very common. Phenothiazine methylene blue (tau protein inhibitor) is currently the only drug under phase III clinical trials. In this work, a non-invasive strategy is presented for modulating the aggregation of core peptide segments of tau protein (VQIVYK and VQIINK) by using electric fields of varying strengths. We use thioflavin T staining, tyrosine fluorescence assay, electron microscopy, IR, dynamic and static light scattering, and neuronal toxicity estimation, for verifying the effect of electric field on the aggregation kinetics, morphology, conformational state and cellular toxicity of peptide systems. Our observations suggest that electric field arrests the self-assembly of VQIVYK and VQIINK fibrils thereby reducing the neurotoxicity instigated by them. Based on our observations, we propose a prospective scheme for a futuristic non-invasive therapeutic device.

Synthesis, characterization and electrochemical analysis of cysteine modified polymers for corrosion inhibition of mild steel in aqueous 1 M HCl

Butler's cyclopolymerization protocol was used to synthesize homo and copolymers of cysteine residues and diallyldimethylammonium chloride (DADMAC) using water as a solvent and excellent yields were obtained. The structural composition of the polymers was determined using nuclear magnetic resonance (NMR) and Fourier-transform infrared (FT-IR) spectroscopies. The thermal stability of the synthesized polymers was determined using thermogravimetric analysis (TGA). The corrosion efficiencies and adsorption characteristics of these polymers on mild steel were evaluated using gravimetric weight loss and potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). The copolymers of cysteine residues and DADMAC exhibited excellent inhibition efficiencies in arresting mild steel corrosion in 1 M hydrochloric acid (HCl) at 60 °C. The best fitted Langmuir, Temkin and Freundlich adsorption isotherms suggested that the adsorption process occurs through chemisorption and physisorption. The surface morphology of mild steel in the presence or absence of polymers was determined using atomic force microscopy (AFM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). This systematic study might provide a way to design new inhibitor compounds that could be beneficial in the field of biomedical science as well as for anti-corrosion applications.

Mild steel framework embedded in corrosion inhibiting structural motifs.

Tailoring the morphological features of sol–gel synthesized mesoporous hydroxyapatite using fatty acids as an organic modifier

Nowadays, owing to their large surface area, enhanced pore volume, increased porosity, and variable pore size, mesoporous materials, such as mesoporous silica and mesoporous carbon, have attracted significant attention in the areas of physical science and biomedical sciences. Due to their compositional and biological similarities to natural tissues, synthetic nanoscaled mesoporous hydroxyapatite (MPHA) nanoparticles possess good biocompatibility, bioactivity, and osteoconductivity and have recently expanded their applicability in a wide range of fields such as in tissue replacement, drug/gene delivery carriers, and biocompatible coatings. In this study, we defined a novel route to synthesize mesoporous hydroxyapatite nanoparticles by the sol–gel method in the presence of stearic acid (SA), a biocompatible medium chain fatty acid that would function as an organic modifier. The as-prepared HAP particles were subjected to structural, functional and morphological characterization. Mesopores in HAP were observed for samples synthesized at pH 11 by removing the organic template. The porosity of HAP was confirmed by the Brunauer–Emmett–Teller (BET) analysis. The apatite deposition phenomenon in simulated body fluid at pH 7.4 confirms their in vitro bioactivity, and based on the in vitro cytotoxicity examined using Vero cell cultures, the as-prepared HAP particles exhibit excellent cytocompatibility and cell viability as high as 83% at an extract concentration as low as 25%. Moreover, the loading and leaching behavior of the drug in mesoporous HAP was studied using methionine (MT), an essential amino acid. These results confirm that nano mesoporous hydroxyapatite loaded with MT can be a potential aspirant as a biomaterial in biomedical applications.

Nowadays, owing to their large surface area, enhanced pore volume, increased porosity, and variable pore size, mesoporous materials, such as mesoporous silica and mesoporous carbon, have attracted significant attention in the areas of physical science and biomedical sciences.

Effect of Variation of Hard Segment Content and Graphene-Based Nanofiller Concentration on Morphological, Thermal, and Mechanical Properties of Polyurethane Nanocomposites

This study describes the development of a new class of high-performance polyurethane elastomer nanocomposites containing reduced graphene oxide (RGO) or graphene nanoplatelets (GNP). Two types of polyurethane elastomers with different contents of hard segments (HS) were used as a polymer matrix. The developed nanocomposites were characterized by thermal analysis (DSC, TG), dynamic mechanical testing (DMA), hardness testing, mechanical properties, rheology, FTIR spectroscopy, XRD, and microscopy investigation (TEM, SEM). Morphological investigation confirmed better compatibility of RGO with the polyurethane (PU) matrix compared to GNP. Both applied nanofillers influenced melting and crystallization of the PU matrix. The nonlinear viscoelastic behavior of the nanocomposites (Payne effect) was studied, and the results were compared with theoretical predictions.

Thermally-healable network solids of sulfur-crosslinked poly(4-allyloxystyrene)

Network polymers of sulfur and poly(4-allyloxystyrene), PAOS_x (x = percent by mass sulfur, where x is varied from 10–99), were prepared by reaction between poly(4-allyloxystyrene) with thermal homolytic ring-opened S₈ in a thiol-ene-type reaction. The extent to which sulfur content and crosslinking influence thermal/mechanical properties was assessed. Network materials having sulfur content below 50% were found to be thermosets, whereas those having >90% sulfur content are thermally healable and remeltable. DSC analysis revealed that low sulfur-content materials exhibited neither a T_g nor a T_m from −50 to 140 °C, whereas higher sulfur content materials featured T_g or T_m values that scale with the amount of sulfur. DSC data also revealed that sulfur-rich domains of PAOS₉₀ are comprised of sulfur-crosslinked organic polymers and amorphous sulfur, whereas, sulfur-rich domains in PAOS₉₉ are comprised largely of α-sulfur (orthorhombic sulfur). These conclusions are further corroborated by CS₂-extraction and analysis of extractable/non-extractable fractions. Calculations based on TGA, FT-IR, H₂S trapping experiments, CS₂-extractable mass, and elemental combustion microanalysis data were used to assess the relative percentages of free and crosslinked sulfur and average number of S atoms per crosslink. Dynamic mechanical analyses indicate high storage moduli for PAOS₉₀ and PAOS₉₉ (on the order of 3 and 6 GPa at −37 °C, respectively), with a mechanical T_g between −17 °C and 5 °C. A PAOS₉₉ sample retains its full initial mechanical strength after at least 12 pulverization-thermal healing cycles, making it a candidate for facile repair and recyclability.

Sulfur and a polystyrene derivative were combined to form thermally-healable and recyclable composite materials with dramatically increased structural integrity versus sulfur alone.

Radiation Crosslinking of Polyurethanes: Characterization by FTIR, TGA, SEM, XRD, and Raman Spectroscopy

Gamma radiation can be used for enhancing the physical properties of polyurethane (PU). Radiation was used to crosslink a polyurethane at room temperature; four samples of the PU solid film are irradiated at variable four radiation doses 0, 50, 100, and 150 kGy under vacuum conditions. Crosslinking radiation is more common than oxidative degradation and crosslinking is believed to be more efficient in the soft segment of PU. The structure of the PUs is performed by Fourier transform infrared (FTIR-ATR), Thermogravimetric Analysis (TGA-DTG), and X-ray Diffraction (XRD) which have been used to investigate the effect of gamma radiation on the polyurethane (PU). The results showed that the radiation crosslinking of polyurethanes improved the thermal stability and the crystallinity. The microstructure modifications of polyurethane samples have also been studied as a function of the dose using the scanning electron microscope (SEM). The effects of gamma irradiation on the color changes of polyurethane were observed. The irradiated PUs have conjugated structure and are capable of emitting purple fluorescence.