A Strategy for Synthesis of Ion‐Bonded Supramolecular Star Polymers by Reversible Addition‐Fragmentation Chain Transfer (RAFT) Polymerization

We have developed a novel strategy for the preparation of ion‐bonded supramolecular star polymers by RAFT polymerization. An ion‐bonded star supramolecule with six functional groups was prepared from a triphenylene derivative containing tertiary amino groups and trithiocarbonate carboxylic acid, and used as the RAFT agent in polymerizations of tert‐butyl acrylate (tBA) and styrene (St). Molecular weights and structures of the polymers were characterized by ¹H NMR and GPC. The results show that the polymerization possesses the character of living free‐radical polymerization and the ion‐bonded supramolecular star polymers PSt, PtBA, and PSt‐b‐PtBA, with six well‐defined arms, were successfully synthesized.

     

Ferric nitrate-promoted oxidative esterification of toluene with N-hydroxyphthalimide: Synthesis of N-hydroxyimide esters

A ferric nitrate-promoted cross-dehydrogenative coupling reaction of N-hydroxyphthalimide (NHPI) with toluene derivatives is reported. The reaction proceeded smoothly using molecular oxygen as an oxidant, providing an efficient method for the synthesis of N-hydroxyimide esters. Furthermore, a plausible mechanism was proposed.     

Voltammetric determination of DNA based on regulation of DNA strand displacement using an allosteric DNA toehold

An electrochemical biosensor for determination of DNA is described that is based on the reaction of regulated DNA (reg-DNA) first with substrated DNA (subs-DNA) to form a reaction intermediate. The intermediate binds target DNA (T) by hybridization and initiates a branch migration leading to the production of complex of substrated DNA and target DNA (TC). Once TC is produced, it reacts with assisted DNA (ass-DNA) through a toehold exchange mechanism, yielding the product complex of substrated DNA and assisted DNA (CS). The target is then released back into the solution and and catalyzes the next cycle of toehold-exchange with the reaction intermediate of substrated DNA and regulated DNA (CPR). Unlike in a conventional DNA toehold that is hardwired with the branch migration domain, the allosteric DNA toehold is designed into a reg-DNA which is independent of the branch migration domain. Under the optimal experimental conditions and at a working potential as low as 0.18 V, response to DNA is linear in the 1 fM to 1000 pM concentration range, and the detection limit is 0.83 fM. The assay is highly specific and can discriminate target DNA even from a single-base mismatch. It was applied to the analysis of DNA spiked plasma samples.

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Graphical abstract Schematic illustration of the electrochemical strategy for target DNA detection based on regulation of DNA strand displacement using an allosteric DNA toehold strategy. It can be used to analyze DNA-spiked plasma samples and has a low detection limit of 0.83 fM.

     

A novel and convenient preparation of antibacterial polyacrylonitrile nanofibers via post-modification using nitrile click chemistry and electrospinning

An efficient, novel and convenient method for the synthesis of modified polyacrylonitrile (PAN) with antibacterial property is reported. The modification of PAN was prepared by a nitrile click chemistry reaction with sodium azide (NaN₃) and silver nitrate (AgNO₃) as catalyst to yield antibacterial polymeric materials with 5-vinyltetrazole units. The results showed that 5-vinyltetrazole units had coordinated with silver ion (Ag⁺). Through the electrostatic spinning technology, the post-modification PAN nanofibers (PAN–Ag⁺ nanofibers) were prepared and the fibers were tested for their antimicrobial properties by the bacterial infection experiment. Afterwards, the antibacterial and stable performance of different proportions of silver ions in PAN nanofibers has been compared. The PAN–Ag⁺ nanofibers are characterized for mechanical and thermomechanical properties, structural analysis, appearance characteristics, as well as the antibacterial properties. And the nanofibers exhibit marvelous chemical stability according to the thermogravimetric analysis. When at 800 °C, the PAN decomposed about 60%, while the decomposition of the PAN–Ag⁺s was 40%. Based on the bacterial infection experiment, PAN–Ag⁺ nanofibers’ antibacterial properties were stronger with the increase of silver ions, such as the number of bacteria clone was smaller and the bacteriostatic ring was larger. Hence, with combination of silver ions, the final polymers show strong antimicrobial properties.     

Geminal Dicationic Ionothermal Synthesis of One Three-Dimensional Luminescent Strontium(II) Coordination Polymer Based on 1,4-Naphthalenedicarboxylate Acid

One three-dimensional Sr(II) coordination polymer [C₆(MIm)₂][Sr₃(1,4-NDC)₄] (I) (C₆(MIm)₂ = 1,3-bis(3-methylimidazolium-1-yl)hexyl, 1,4-H₂NDC = 1,4-naphthalenedicarboxylate acid) has been synthesized using an ionothermal method and structurally characterized by IR spectroscopy, UV-Vis spectroscopy, XRPD, and X-ray single-crystal structure analysis (СIF file CCDC 1033958). Two types of strontium centers are bridged by two coordination modes of 1,4-H₂NDC ligands to form a Sr(II) chain. Each Sr(II) chain is crossconnected to four other chains to generate a 3D coordination polymer, in which C₆(MIm) ₂ ²⁺ cations as charge balancing species are filled in the channels of the anionic framework. The polymeric solid of I exhibits strong luminescent emission at room temperature.     

Effect of π–π interaction between carbon nanotubes and phenyl groups on the thermal stability of silicone rubber

Journal of Thermal Analysis and Calorimetry - To investigate the effect and mechanism of π–π interaction between carbon nanotubes (CNTs) and phenyl groups on the thermal stability...     

High-efficiency nonvolatile holographic storage with two-step recording in praseodymium-doped lithium niobate by use of continuous-wave lasers

We have observed efficient two-photon, two-step recording in a praseodymium-doped lithium niobate crystal by use of cw lasers. Single-photon erasure during the readout at near-infrared wavelengths was found to be negligible. Nonvolatile holographic image storage was demonstrated. This progress is an important step in the realization of an economically feasible nonvolatile read-write holographic recording system based on low-cost semiconductor diode lasers.     

Site-specific binding of chelerythrine and sanguinarine to single pyrimidine bulges in hairpin DNA

Spectrofluorometric titration, electrospray ionization time-of-flight mass spectrometric and UV melting methods were employed to study the binding of chelerythrine and sanguinarine to bulged DNA. The results showed that both alkaloids bind specifically to single pyrimidine (C, T) bulge sites. The ability of sanguinarine to bind to both regular and bulged hairpins was found to be stronger than that of chelerythrine, but the binding selectivity of chelerythrine toward single-base bulges was much larger than that of sanguinarine. Figure Association constants for chelerythrine and sanguinarine toward regular and single-base bulged hairpins obtained from fluorometric analysis