新型功能碳材料的高压截获

高性能功能材料在诸多领域具有广泛的应用前景,是人们一直关注的研究热点。高压可以有效地改变物质的原子间距和成键方式,是获得新型功能材料的重要途径。在碳材料的高压研究中,许多有趣的功能碳材料,如光学透明碳、高强度弹性碳和超硬非晶碳等,已经通过不同的碳前驱体合成。本文简要介绍了作者近年来在低维碳基纳米复合材料高压研究中取得的进展,基于设计的不同低维碳前驱体,高压下截获了具有超硬特性、新型压致共价聚合及发光增强的碳材料。     

o-Trityl phenoxy-imino vanadium (III) complexes: synthesis,characterization, and catalysis on ethylene (co)polymerization

Several phenoxy-imine ligands bearing o-trityl group in phenoxy moiety RN=CHArOH (Ar = C₆H₂(CPh₃)^tBu, R = 2,6-Me₂C₆H₃ ( L ₁ H ); 2,6-ⁱPr₂C₆H₃ ( L ₂ H ); 3,5-(CF₃)₂C₆H₃ ( L ₃ H ); 3,5-(OMe)₂C₆H₃ ( L ₄ H ); CHPh₂ ( L ₅ H ); CPh₃ ( L ₆ H )) were synthesized and characterized by¹H NMR and ¹³C NMR spectroscopy. The vanadium complexes based on these ligands LVCl₂(THF)₂ ( 1–6 ) were synthesized via conventional transmetalation reaction in moderate to high yields. Complexes 1–6 were fully characterized by FT-IR, elemental analyses and the molecular structures of 1 , 2 ·H₂O, (2 ·H₂O ) ₂ (μ-Cl) ₂ , 4 , and 5 were confirmed by X-ray crystallographic analysis in which the six-coordinated vanadium centers are in a typical octahedral geometry. Upon activation with Et₂AlCl in toluene, complexes 1–6 showed high activities in ethylene polymerization affording polymers with moderate molecular weight (5.9–11.8 × 10⁴ Da). Moreover, in hexane or CH₂Cl₂, 1–6 /Et₂AlCl exhibited enhanced activities. When activated with MAO or MMAO in toluene, these complexes showed relatively low activities but afforded polymers with ultra-high molecular weight (up to 3.30 × 10⁶ Da). 1–6 /Et₂AlCl also showed high activities in ethylene/1-hexene copolymerization at room temperature giving moderate molecular-weight polymers (6.5–11.4 × 10⁴ Da) with co-monomer incorporation being of 6.0 ~ 7.8%.     

Facile synthesis of graft copolymers containing rigid poly(dialkyl fumarate) branches by macromonomer method

Graft copolymers show microphase separated structure as seen in block copolymers and have lower intrinsic viscosity than block copolymers because of a branching structure. Therefore, considering molding processability, especially for polymers containing rigid segments, graft copolymers are useful architectures. In this work, graft copolymers containing rigid poly(diisopropyl fumarate) (PDiPF) branches were synthesized by full free‐radical polymerization process. First, synthesis of PDiPF macromonomers by addition‐fragmentation chain transfer (AFCT) was investigated. 2,2‐Dimethyl‐4‐methylene‐pentanedioic acid dimethyl ester was found to be an efficient AFCT agent for diisopropyl fumarate (DiPF) polymerization because of the suppression of undesired primary radical termination, which significantly took place when common AFCT agent, methyl 2‐(bromomethyl)acrylate, was used. Copolymerization of PDiPF macromonomer with ethyl acrylate accomplished the generation of the graft copolymer having flexible poly(ethyl acrylate) backbone and rigid PDiPF branches. The graft copolymer showed a microphase separated structure, high transparency, and characteristic thermal properties to PDiPF and poly(ethyl acrylate). © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2474–2480     

Modeling of Anionic Polymerization of Isoprene in an Industrial Reactor

One of the most important reasons for modeling polymerization processes is to provide a tool for estimating the risks of runaway reactions in polymer industry. This is especially important for batch processes, such as anionic polymerization of isoprene or butadiene. This work presents a theoretical and experimental research of the anionic polymerization of isoprene using cyclohexane as solvent and n‐butyllithium as initiator. In the first part, a phenomenological kinetic expression is obtained that describes the anionic polymerization of isoprene initiated by n‐butyllithium in cyclohexane. In the second, the mass and energy balance equations are solved to model the anionic polymerization of isoprene in a quasi‐adiabatic batch reactor. Adjustment of reactor parameters is made using the data obtained from a laboratory reactor. The proposed model predicts adequately the obtained temperature, pressure, and conversion profiles from this set of experiments. Finally, a mathematical model is developed to predict the behavior for the anionic polymerization of isoprene in an industrial reactor.     

A New Approach for the Synthesis of Miktoarm Star Polymers Through a Combination of Thiol–Epoxy “Click” Chemistry and ATRP/Ring‐Opening Polymerization Techniques

A new approach was developed for synthesis of certain A₃B₃‐type of double hydrophilic or amphiphilic miktoarm star polymers using a combination of “grafting onto” and “grafting from” methods. To achieve the synthesis of desired miktoarm star polymers, acetyl protected poly(ethylene glycol) (PEG) thiols (M_n = 550 and 2000 g mol^?1) were utilized to generate A₃‐type of homoarm star polymers through an in situ protective group removal and a subsequent thiol–epoxy “click” reaction with a tris‐epoxide core viz. 1,1,1‐tris(4‐hydroxyphenyl)ethane triglycidyl ether. The secondary hydroxyl groups generated adjacent to the core upon the thiol–epoxy reaction were esterified with α‐bromoisobutyryl bromide to install atom transfer radical polymerization (ATRP) initiating sites. ATRP of N‐isopropylacrylamide (NIPAM) using the three‐arm star PEG polymer fitted with ATRP initiating sites adjacent to the core afforded A₃B₃‐type of double hydrophilic (PEG)₃[poly(N‐isopropylacrylamide)] (PNIPAM)₃ miktoarm star polymers. Furthermore, the generated hydroxyl groups were directly used as initiator for ring‐opening polymerization of ε‐caprolactone to prepare A₃B₃‐type of amphiphilic (PEG)₃[poly(ε‐caprolactone)]₃ miktoarm star polymers. The double hydrophilic (PEG)₃(PNIPAM)₃ miktoarm star polymers showed lower critical solution temperature around 34 °C. The preliminary transmission electron microscopy analysis indicated formation of self‐assembly of (PEG)₃(PNIPAM)₃ miktoarm star polymer in aqueous solution. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 146–156     

Unsymmetrically substituted ethane as a new and efficient initiator for the polymerization of methyl methacrylate and styrene

In this paper, we present a compound, 2,3-diphenyl butyronitrile (DPBN), which can be used as a new and efficient radical initiator for the polymerization of methyl methacrylate (MMA) and styrene (St). Very different from other compounds as a carbon-carbon initiator, DPBN is an unsymmetrically substituted ethane and works with high initiation reactivity at lower temperatures. This new compound as an initiator exhibits various advantages, such as easy preparation, high initiation reactivity, safe use and storage, and convenient handling.     

Facile synthesis of polyacrylate directed silver nanoparticles for pH sensing through naked eye

Poly(acrylic acid) (PAA) and its salt poly(acrylate) (PA) have been synthesized through modified free radical polymerization in environmentally begin aqueous medium under ultrasound to make the process robust. The synthesized polymer is well-characterized through conventional techniques. Its salt is employed to produce highly stable and stimuli sensitive colloidal silver (Ag-PA sol) without using any additional reducing chemical reagents like sodium borohydride, ascorbic acid, hydrazine, etc or UV/Gamma radiation. A detailed mechanistic path of the polymerization and reduction of Ag⁺ on polyacrylate chains has been evaluated. Finally Ag-PA sol is used for pH sensing through naked eye to eliminate the need for sophisticated instrument for data collection. The present work focuses mainly the development of a low cost pH sensing system based on colorimetric ‘smart polymer’ having high practical utility. The unique structural and photo-physical features of nano-scaled materials open new opportunities for the applications of colorimetric pH sensor. In the present work, Ag nano-clusters capped by PA^? are employed as an effective colorimetric pH sensor for the first time, requiring no further functionalization.     

Condensed Mode Cooling of Ethylene Polymerization in Fluidized Bed Reactors

This review gives an overview of the evolution of the technology of condensed mode cooling, primarily for the case of ethylene polymerization on supported catalysts in fluidized bed reactors. It is well known that this mode of heat removal is quite effective in allowing polyolefin manufacturers to increase significantly production rates. What is perhaps less well understood are all of the issues that, in addition to the effect of the latent heat of vaporization of injected liquid components, also have an impact on the rate of production and behavior of the reactor. However, the liquid components injected into the reactor can vaporize rapidly under full‐scale conditions, leaving behind several heavy components (with respect to ethylene) that have numerous effects on how the particles behave, on the reaction rate, and on fluidization, fouling, and other parameters related to reactor and process performance.     

Nanocrystalline cellulose/fluorinated polyacrylate latex via RAFT‐mediated surfactant‐free emulsion polymerization and its application as waterborne textile finishing agent

A simple method for nanocrystalline cellulose (NCC)/fluorinated polyacrylate was developed by RAFT‐mediated surfactant‐free emulsion polymerization, in which the nanocomposites formed a core‐shell spherical morphology. The influence of the content of NCC‐g‐(PAA‐b‐PHFBA) (AA was acrylic acid, HFBA was hexafluorobutyl acrylate) on the properties of latex and film were systematically studied. The monomer conversion, the tensile strength, and water–oil repellency of film increased first and then decreased, the latex particle size decreased first and then decreased, when the content of NCC‐g‐(PAA‐b‐PHFBA) increased from 1 to 6 wt %. Elongation at break and thermal stability distinctly decreased when the content of NCC‐g‐(PAA‐b‐PHFBA) gradually increased. XPS showed that the fluorine‐containing groups well concentrated at the film–air interfaces during the annealing process. SEM analysis revealed that the treated fiber had a rugged surface, and the treated fabric had an excellent water repellency. In addition, this green grafting method in water offered a new perspective for the fabrication of exceptional NCC‐based nanocomposites with NCC as the core and also helped to promote the potential applicability of NCC in a range of multipurpose applications. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1305–1314     

Switching from linear to cyclic δ‐Polyvalerolactone synthesized via zeolitic imidazolate framework as a catalyst: A promising approach

A series of spray dried zeolitic imidazolate frameworks (ZIFs = ZIF‐8, ZIF‐67, and Zn/Co‐ZIF) are used as a catalyst for the bulk ring‐opening polymerization of δ‐valerolactone without any co‐catalyst to generate polyvalerolactone. Interestingly, using the same catalyst under the same reaction conditions could manipulate the structure of the product polymer, and thus its physical properties. Thus, using a dried substrate leads to the formation of the cyclic polymer while a linear polymer was formed on using the commercially available substrate. An activated monomer mechanism has been suggested where the propagating zinc alkoxide undergoes an intramolecular transesterification to release cyclic or linear polyvalerolactone. The ROP of δ‐VL without drying shows that the polymeric zwitterions have little tendency to cyclize in the presence of moisture. At 140 °C, ZIF‐8 shows a superior catalytic activity resulting in the production of cyclic polyvalerolactone having a high molecular weight as compared to ZIF‐67 or Zn/Co‐ZIF due to the presence of highly active sites. The catalyst could be recycled and reused without any significant loss of catalytic activity.