Antibacterial behaviour of quaternized poly(vinyl chloride)-g-poly(4-vinyl pyridine) graft copolymers

Amphiphilic graft copolymers consisting of poly(vinyl chloride)(PVC) main chains and poly(4-vinyl pyridine)(P4VP) side chains were synthesized via atom transfer radical polymerization(ATRP) using direct initiation of chlorine atoms. The successful synthesis of PVC-g-P4 VP graft copolymers was confirmed by Fourier transform infrared spectroscopy(FTIR) and proton nuclear magnetic resonance(1H-NMR). Transmission electron microscope(TEM) and small angle X-ray scattering(SAXS) analysis showed that PVC-g-P4 VP exhibited microphase-separated, ordered structure with 37.6 nm of domain spacing, which was not observed in neat PVC. For antibacterial applications, the tertiary nitrogen atoms of PVC-gP4 VP was quaternized using 1-bromohexane, as confirmed by FTIR measurements. Bacteria including Escherichia coli(E. coli), Staphylococcus aureus(S. aureus), Bacillus cereus(B. cereus), and Pseudomonas aeruginosa(P. aeruginosa) were completely killed in 24 h on the quaternized PVC-g-P4VP(46% grafting) surface, indicating its excellent antibacterial behavior while it showed to be cytotoxic to mammalian cell.     

Molecular Architecture Manipulation in Free Radical Copolymerization: An Advanced Monte Carlo Approach to Screening Copolymer Chains with Various Comonomer Sequence Arrangements

A Kinetic Monte Carlo (KMC) simulation approach has been adopted in this study to capture evolutionary events in the course of free radical copolymerization, through which batch and starved‐feed semibatch processes are compared. The implementation of the KMC code deve­loped in this work: (i) enables satisfactory control of the molecular weight of the copolymer by tracking the profiles of concentrations of macroradicals, monomers, and polymer as well as degree of polymerization, polydispersity, and chain length distribution; (ii) captures the bivariate distribution of chain length and copolymer composition; (iii) comprehensively tracks and analyzes detailed information on the molecular architecture of the growing chains, thus distinguishing between sequence length and polydispersity of chains produced in batch and starved‐feed semibatch operations; (iv) makes possible the screening of products, based on such details as the number and weight fractions of products having different comonomer units located at various positions along the copolymer chains. The aforementioned characteristics are achieved by stochastic calculations through code developed in‐house. This KMC simulator becomes a very useful tool for the development of tailored copolymers through free radical polymerization, with blocks separated with single units of a different type.

     

Polyaniline‐Induced CH Arylation of Arenes with Arenediazonium Salts

A reduced form of polyaniline has been shown to induce direct arylation of an arenediazonium salt with an arene (Gomberg–Bachmann reaction) to give the cross‐coupling product in moderate to good yields under mild conditions. Various arenediazonium salts and arenes, including heteroarenes such as furans, thiophenes, and pyrroles, are employed for the reaction. The most favorable combination of substrates is an electron‐poor arenediazonium salt with an electron‐rich heteroarene. Investigation of the mechanism by reactions with radical scavengers and experiments on kinetic isotope effects indicated the occurrence of a radical chain reaction initiated by one‐electron reduction of an arenediazonium salt by the polyaniline. Only 1 mol % (based on aniline tetramer) of the polyaniline is required for the cross‐coupling reaction to occur. This reaction proceeds under metal‐free conditions and with no need for photonic activation.     

Metal‐Chelating N,N′‐Bis(4‐dimethylaminophenyl)acetamidinyl Radical: A New Chromophore for the Near‐Infrared Region

A new non‐innocent ligand redox system, N,N′‐bis(4‐dimethylaminophenyl) substituted acetamidinato/acetamidinyl, has been designed and described by example of structurally and spectroscopically characterized ruthenium complexes. The hitherto unreported ligand is responsible for rather intense and narrow absorptions in the near‐infrared region of the one‐ and two‐electron oxidized forms. The spectroscopic, computational, and first structural characterization of an amidinyl radical complex adds to the list of established N‐based radical ligands.     

Asymmetric Total Synthesis of ent‐Pyripyropene A

An asymmetric total synthesis of ent‐pyripyropene A was achieved by a convergent synthetic route. We used our originally developed Ti^III‐catalyzed radical cyclization to construct an AB‐ring portion that consisted of a trans‐decalin skeleton with five contiguous stereogenic centers. The coupling between the AB‐ring and the DE‐ring portions, and a subsequent C‐ring cyclization, led to the total synthesis of ent‐pyripyropene A. An evaluation of the insecticidal activity of ent‐pyripyropene A against two aphid species revealed that ent‐pyripyropene A was 35–175 times less active than naturally occurring pyripyropene A. This result indicated that the biological target of pyripyropene A recognizes the absolute configuration of pyripyropene A.     

Dioxygen‐Mediated Decarbonylative CH Alkylation of Heteroaromatic Bases with Aldehydes

An operationally simple and economical method for the direct alkylation of heteroaromatic bases employing readily available aldehydes as alkyl radical precursors and molecular oxygen as a reagent is presented. This simple transformation demonstrates a broad substrate scope with respect to aldehydes and nitrogen heterocycles, enabling the introduction of several medicinally important yet challenging alkyl moieties, such as ethyl, isopropyl, tert‐butyl, and cyclohexyl to the different classes of heterocyclic bases in good to excellent yields.     

铜催化烯烃氰烷基化成环合成含氰吲哚酮

发展一种简单、高效的铜催化活泼烯烃氰烷基化成环合成吲哚酮的方法。 在CuI/DTBP(叔丁基过氧化物)催化作用下, N-芳基丙烯酰胺类化合物与α-氰基偶氮试剂发生自由基环化反应, 高效地合成了一系列含α-氰基季碳中心的吲哚酮, 并探讨了其反应机理。 该方法底物适用范围较广、反应体系温和, 催化体系廉价。     

一种温敏型超大孔生物分离介质的制备及表征

采用改性琼脂糖对超大孔聚苯乙烯微球进行亲水化修饰(Agap-PS),通过酰基化反应在微球表面引入溴乙酰基(Agap-PS-Br),然后利用原子转移自由基聚合(ATRP)反应在Agap-PS-Br表面接枝温敏聚合物刷,得到一种温敏型超大孔生物分离介质(Agap-PS-PNIPAM).考察了配体、催化剂、溶剂和温度对N-异丙基丙烯酰胺ATRP反应的影响,在优化条件下PNIPAM的接枝量达到了15.07 mg/m2.采用红外光谱(FTIR)、扫描电镜(SEM)、压汞分析、激光共聚焦和蛋白吸附等手段对温敏型超大孔生物分离介质进行一系列表征,结果表明接枝温敏聚合物刷后Agap-PS-PNIPAM具有良好的温敏性,没有堵塞微球的超大孔,微球对蛋白的非特异性吸附大大降低.由于温敏聚合物刷发生了从亲水到疏水构象的转变,40℃时Agap-PS-PNIPAM对蛋白的吸附量是25℃时的2.69倍.压力流速实验表明Agap-PS-PNIPAM柱具有背压低、渗透性和机械稳定性好的优点,同样地由于PNIPAM链在40℃时收缩,此时Agap-PS-PNIPAM柱的床层渗透系数比25℃时提高了15.7％.     

Self‐Assembled Colloidal Particle Clusters from In Situ Pickering‐Like Emulsion Polymerization via Single Electron Transfer Mechanism

A simple route is reported to synthesize colloidal particle clusters (CPCs) from self‐assembly of in situ poly(vinylidene fluoride)/poly(styrene‐co‐tert‐butyl acrylate) [PVDF/P(St‐co‐tBA)] Janus particles through one‐pot seeded emulsion single electron transfer radical polymerization. In the in situ Pickering‐like emulsion polymerization, the tBA/St/PVDF feed ratio and polymerization temperature are important for the formation of well‐defined CPCs. When the tBA/St/PVDF feed ratio is 0.75 g/2.5 g/0.5 g and the reaction temperature is 35 °C, relatively uniform raspberry‐like CPCs are obtained. The hydrophobicity of the P(St‐co‐tBA) domains and the affinity of PVDF to the aqueous environment are considered to be the driving force for the self‐assembly of the in situ formed PVDF/P(St‐co‐tBA) Janus particles. The resultant raspberry‐like CPCs with PVDF particles protruding outward may be promising for superhydrophobic smart coatings.

     

Poly(paraphenylene sulfide) and Poly(metaphenylene sulfide) via Light‐Initiated SRN1‐Type Polymerization of Halogenated Thiophenols

In this work, the synthesis of various halogenated thiophenol derivatives is presented. These thiophenols are used as monomers in light‐initiated S_RN1‐type radical polymerization reactions. The method provides easy access to industrially relevant poly(paraphenylene sulfide) and poly(metaphenylene sulfide). The influence of the halide leaving group and of other substituents in the thiophenol monomer on the polymerization process is investigated.