Coacervation of copolymer of diallyldimethylammonium chloride and sodium styrenesulfonate aqueous solution

Coacervate behavior of polyelectrolyte complexes has been studied by many papers. Few studies have focused on the coacervate behavior of amphoteric polymer. In this study, amphoteric copolymer of diallyldimethylammonium chloride (DM) and sodium styrenesulfonate (SS) (the copolymer was noted as DMS) was synthesized with the mole content of SS to DM ranged from 0 to 10%. Firstly, DMS was characterized by static light scattering, FTIR, ¹H-NMR, TGA and DSC. Then, its phase and coacervate behaviors were studied. Turbidity was utilized as an indicator for the coacervate formation. It was found that when the SS content was more than 4 mol%, DMS coacervate would be formed in deionized water at a certain concentration. Temperature and pH have no effect on the formation of DMS coacervate. Meanwhile, salts has a great influence on the DMS coacervation. Unlike the results of the other polyelectrolyte complexes, Na₂SO₄, Na₂HPO₄, NaCOOCH₃, sodium citrate and NaI cannot prevent the DMS coacervate formation. However, the addition of NaCl, NaNO₃, NaBr and NaSCN can prevent the coacervate formation. The influence cannot be described by Hofmeister-like behavior. Results of surface tension and fluorescence spectrum presented that the driving forces to formation of DMS coacervate are the electrostatic interaction and the intermolecular hydrophobic interaction.     

A theoretical prediction about harnessing ESPT process for HBO derivatives

The different excited-state behaviors involved in excited-state proton transfer (ESPT) process of a series of 2-(2-hydroxyphenyl)benzoxazole (HBO) derivatives have been theoretically investigated. The primary bond lengths and bond angles were analyzed. Coupling with the infrared (IR) vibrational spectra, we confirmed that the intramolecular hydrogen bond O–H···N should be strengthened in the S₁ state, which might provide the possibility for ESPT reaction, whereas introducing the fused rings may weaken the hydrogen bond in excited state. By investigating the vertical excitation process, the charge redistribution was explored. It is found that the electron-accepting –NO₂ and –COOH would facilitate the ESPT reaction. With adding fused rings to HBO, less charge transfer exists in the transition process, which can reasonably explain the weakening hydrogen bond phenomenon in excited states. Via constructing the potential energy curves of both S₀ and S₁ states, we further confirm that electron-accepting substitutions could promote the ESPT process for HBO systems. And fused rings do inhibit ESPT reaction to a great extent. We believe this work not only elaborates the different excited-state proton transfer behaviors for a series of HBO derivatives but also presents a new harnessing ESPT process through substitutional effects.     

Potassium Amide‐Catalyzed Benzylic C−H Bond Addition of Alkylpyridines to Styrenes

The benzylic functionalization of alkylpyridines is an important pathway for pyridine derivatives synthesis. The reaction partners, however, were mostly limited to highly reactive polar electrophiles. Herein, we report a potassium amide‐catalyzed selective benzylic C?H bond addition of alkylpyridines to styrenes. Potassium bis(trimethylsilyl)amide (KHMDS), a readily available Brønsted base, showed excellent catalytic activity and chemoselectivity. A series of alkylpyridine derivatives, including benzylic quaternary carbon substituted pyridines, were obtained in good to high yield. Preliminary mechanistic studies revealed that the deprotonation equilibrium is probably responsible for the excellent selectivity.     

Influence of Gemini Surfactant with Modified TiO2 Nanoparticles on the Interfacial Tension of Oil/Water

The research on the impacts of modified TiO₂ nanoparticles (NPs) on interfacial tension (IFT) is in its infancy. Our work focuses on the IFT of the modified TiO₂ and Gemini surfactant N,N,N′,N′-tetramethyl-N,N′-dimyristyl-1,2-ethane diammonium dichlone (YND1233) complex solutions for reservoir stimulation purposes. The factors of YND1233, modified TiO₂ NPs, temperature, aging stability, adsorption loss, and mineralized degree were explored with the comparison of unmodified TiO₂ NPs and YND1233 as contrast samples. The results indicate that the dynamic IFTs decrease and then increase with the concentrations of YND1233 and modified TiO₂ NPs, and the minimum IFT appears at 0.200 and 0.010 wt%, respectively. YND1233/modified TiO₂ complex solutions show lower and more stable IFTs, better temperature resistance, longer aging time, and lower adsorption on the surface of quartz sand. The modified TiO₂ NPs and YND1233 in the YND1233/modified TiO₂ complex solution can be adsorbed to the interface and decrease the IFTs through synergistic effect. A mixed diffusion-kinetic mechanism is provided for the adsorption and interactions with Ca²⁺/Mg²⁺ involved in YND1233/modified TiO₂ complex solution.     

Copper-Catalyzed Si-H Bond Insertion Polymerization for Synthesis of Optically Active Polyesters Containing Silicon

The synthesis and characterization of chiral polymers with diverse structure remain a long-term challenging research topic.Herein,a copper-catalyzed enantioselective insertion of carbene into Si-H bond was applied to polycondensation,giving a new type of optically active degradable polyesters containing Si-C bond in the main chain.The polymerization features mild condition,broad substrate scope,excellent yields and enantioselectivities.Chiral diols could be obtained via reduction of optically active polyesters.Thermogravimetric analysis indicated these chiral polyesters exhibit good thermal stability.     

Dye-sensitized solar cells based on ordered titanate nanotube films fabricated by electrophoretic deposition method

Dye-sensitized solar cells (DSSCs) are fabricated based on ordered titanate nanotube (TNT) films obtained by electrophoretic deposition (EPD) method. Calcination temperatures show a great influence on the performance of TNT solar cells. At 300 °C, the cells exhibit very low photo-electric conversion efficiency. At 400 °C, the efficiency obviously increases. At 600 °C, the cells show the highest efficiency, which is higher than the efficiency of the cells made from commercial-grade Degussa P25 TiO₂ nanoparticles (P25).     

Monodisperse,submicrometer-scale platinum colloidal spheres with high electrocatalytic activity

Monodisperse, submicrometer-scale platinum (Pt) colloidal spheres were prepared through a simple direct chemical reduction of p-phenylenediamine (PPD)-chloroplatinic acid (H₂PtCl₆) coordination polymer colloids. It was found that the prepared Pt colloids had the similar size and morphology with their coordination polymer precursors, and the prepared Pt colloids with rough surfaces were three-dimensional (3D) structured assemblies of high-density small Pt nanoparticles. The electrochemical experiments confirmed that the prepared Pt colloids possessed a high electrocatalytic activity towards mainly four-electron reduction of dioxygen to water, making the prepared Pt colloids potential candidates for the efficient cathode material in fuel cells.     

Two New On-Purpose Processes Enhancing Propene Production: Catalytic Cracking of C4 Alkenes to Propene and Metathesis of Ethene and 2-Butene to Propene

A brief review of the work carried out at Dalian Institute of Chemical Physics, Chinese Academy of Sciences for development of two new on-purpose processes enhancing propene production is presented. This includes the processes of catalytic cracking of C₄ alkenes to propene and metathesis of ethene and 2-butene to propene, by which the large amounts of the C₄ recourses from the petrochemical can be upgraded and the severity of demand for propene can be lessened.     

Nafion–graphene nanocomposite film as enhanced sensing platform for ultrasensitive determination of cadmium

In this work, an ultrasensitive platform for the detection of cadmium (Cd²⁺) combining the nafion–graphene nanocomposite film with differential pulse anodic stripping voltammetry (DPASV) analysis was presented. It is found that this sensing platform exhibits enhanced response to the determination of the Cd²⁺ and has been used to determine the Cd²⁺ in real sample with good recovery.