Synthesis and Characterization of the Polyacrylonitrile-block-poly（methyl acrylate） by RAFT Technique

Reversible addition-fragmentation chain transfer polymerization (RAFT) was firstly reported in 1998 by Rizzardo1. This technique provided the possibility to synthesize polymers with controlled molecular weight, narrow molecular weight distribution, and we…     

Free Radical Polymerization of Acrylonitrile in Green Ionic Liquids

Free radical polymerization of acrylonitrile (AN) in ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]), 2,2;m1-azobisisobutyronitrile (AIBN) as initiator was investigated. Early investigations on polymerizations using ionic liquids indicate that they serve as especially good solvents to achieve high molecular weight polymers. Free radical polymerizations result in higher molecular weight polymers, for ionic liquids have low chain transfer constants and act to stabilize the active radical during the process of polymerization. The thermal stability of polymers synthesized in ionic liquids have be improved obviously than that in traditional solvents.     

丙烯腈在Cu(100)表面化学吸附的密度泛函理论研究

利用密度泛函方法, 模拟金属铜原子簇Cu₁₄(9,4,1)的(100)表面, 对丙烯腈(CH₂＝CHCN)在Cu(100)面上不同吸附位的吸附状况进行了理论研究. 结果表明: 丙烯腈分子通过端位N原子垂直吸附在金属表面上为弱化学吸附, 部分电荷从丙烯腈分子转移至铜金属簇; 由N原子的孤对电子与金属铜形成弱σ共价键; 顶位是最佳吸附位, 吸附能为40.7391 kJ•mol^－1, N原子与金属表面间的平衡距离为0.2279 nm; 其次为桥位和穴位, 吸附能分别为36.2513和30.2158 kJ•mol^－1, 平衡距离为0.2194和0.2886 nm; 吸附后C≡N键的强度降低, 活化了丙烯腈分子. 化学吸附使体系的熵减小, 是由于丙烯腈分子的平动和转动因吸附而被限制.     

Cobalt‐Mediated Radical Polymerization of Vinyl Acetate and Acrylonitrile in Supercritical Carbon Dioxide

Cobalt‐mediated radical polymerization (CMRP) of vinyl acetate (VAc) is successfully achieved in supercritical carbon dioxide (scCO₂). CMRP of VAc is conducted using an alkyl‐cobalt(III) adduct that is soluble in scCO₂. Kinetics studies coupled to visual observations of the polymerization medium highlight that the melt viscosity and PVAc molar mass (M_n) are key parameters that affect the CMRP in scCO₂. It is noticed that CMRP is controlled for M_n up to 10 000 g mol⁻¹, but loss of control is progressively observed for higher molar masses when PVAc precipitates in the polymerization medium. Low molar mass PVAc macroinitiator, prepared by CMRP in scCO₂, is then successfully used to initiate the acrylonitrile polymerization. PVAc‐b‐PAN block copolymer is collected as a free flowing powder at the end of the process although the dispersity of the copolymer increases with the reaction time. Although optimization is required to decrease the dispersity of the polymer formed, this CMRP process opens new perspectives for macromolecular engineering in scCO₂ without the utilization of fluorinated comonomers or organic solvents.

     

气相色谱–质谱联用法测定空气中的丙烯腈

建立测定空气中丙烯腈的气相色谱–质谱联用方法。用活性炭管采集样品,以体积分数为2%的丙酮二硫化碳溶液解吸,利用气相色谱–质谱法以选择离子扫描方式采集数据并进行分析,以色谱峰面积外标法定量。丙烯腈的质量浓度在0~100μg/m L范围内与色谱峰面积线性关系良好,线性相关系数(r~2)为0.999 0。丙烯腈检出限为1.2μg/m L,最低检出质量浓度为0.16 mg/m~3(以采样体积7.5 L计),平均加标回收率为97.0%~99.3%,测定结果的相对标准偏差为3.0%~4.2%(n=6)。该方法定性、定量准确,精密度、灵敏度高,可用于空气中丙烯腈的常规检测。     

Synergistic effect of polyfunctional silane coupling agent and styrene acrylonitrile copolymer on the water‐resistant and mechanical performances of glass fiber–reinforced polyamide 6

Adverse effects of a high‐water absorption rate on properties of a glass fiber–reinforced polyamide 6 (GF‐PA6) composite significantly reduce performance and limit application in humid environments. In this paper, a polyfunctional silane (PFS) coupling agent with amino (–NH₂) and imino (–NH) groups and styrene acrylonitrile copolymer (SAN) were added to a composite, GF‐PA6, to prepare GF‐PA6/SAN/PFS composites via melt blending in a twin‐screw extruder. The effects of SAN and PFS content on the static and dynamic mechanical properties of the composites before and after water absorption were investigated in detail. The microstructure of the fracture surface was analyzed by a scanning electron microscope (SEM). The results show that the addition of SAN and PFS could effectively inhibit water absorption of the GF‐PA6 composites. The alkoxyl groups on PFS reacted chemically with the nitrile groups of SAN, which enriched SAN on the interface between the fiber and matrix during the extrusion and mixing process to improve the effect of water prevention. Therefore, the mechanical properties of the wet state were notably improved while preventing water from permeating the interface by only the addition of a small amount of SAN and PFS. Dynamic mechanical analysis (DMA) results showed that the addition of PFS improved the compatibility of PA6 with SAN and enhanced the interface adhesion between fiber and PA6. In terms of test result of the comprehensive performance, 10 phr SAN with 0.6 phr PFS was the best dosage.     

A Detailed investigation of the experimental conditions for the reversible addition fragmentation chain transfer‐mediated copolymerization of acrylonitrile and butadiene

The synthesis of acrylonitrile‐butadiene rubbers (NBRs) via trithiocarbonate‐mediated reversible addition fragmentation chain transfer (RAFT) polymerization of acrylonitrile (ACN) and 1,3‐butadiene (BD) in solution under azeotropic conditions (38/62) was investigated for a broad range of common solvents: N,N‐dimethylacetamide (DMAc), chlorobenzene, 1,4‐dioxane, tert‐butanol, isobutyronitrile, toluene, trimethylacetonitrile, dimethyl carbonate, acetonitrile, methyl acetate, acetone, and tert‐butyl methyl ether. The gravimetrically determined conversions for the free radical polymerizations of ACN/BD after 22 h at 100 °C were in the range of 15% for methyl acetate to 35% for DMAc. The origin of the differences in conversion is attributed to the unequal decomposition behavior of the employed azo initiator 2,2′‐azobis(N‐butyl‐2‐methylpropionamide) ( 1 ) in the solvents under investigation, as determined by ultraviolet–visible (UV–vis) spectroscopy. Relative decomposition of 1 in solution (0.1 mol L^?1) at 100 °C was calculated from the UV–vis spectra for selected solvents. 90% of 1 in DMAc was decomposed after 22 h, 83% in tert‐butanol, 57% in 1,4‐dioxane, 53% in isobutyronitrile, 45% in chlorobenzene, and 21% in toluene. The evolution of molecular weight with conversion using the initiator 1 was in accordance with the theoretically expected values, regardless of the solvent studied. Moreover, the RAFT‐mediated copolymerization of ACN/BD in DMAc with azo initiators 1 , 1‐[(1‐cyano‐1‐methylethyl)azo]formamide ( 2 ) and 1,1′‐azobis(cyclohexanecarbonitrile) ( 3 ) was investigated. A strong deviation from the linear evolution of molecular weight due to a fast decomposition of these initiators – congruent with high primary radical delivery rates – at the selected temperature was observed when using 2 and 3 . The deviation was not observed when using 1 . © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

“Nascent” Cu(0) nanoparticles‐mediated single electron transfer living radical polymerization of acrylonitrile at ambient temperature

Zn(0)/ppm concentrations of CuBr₂ from 10 to 50 ppm was firstly used to catalyze radical polymerization of acrylonitrile at ambient temperature. The polymerization displayed typical living radical polymerization (LRP) characteristics, as evidenced by pseudo first‐order kinetics of polymerization, linear increase of number‐average molecular weight, and low polydispersity index (PDI) value. Effects of solvent, copper concentration, and initiator concentration on the polymerization reaction and molecular weight as well as PDI were investigated in detail. EC excelled NMP, DMF, and DMSO in terms of rate of polymerization as well as control of molecular weight and PDI. The increase of the copper concentration from 2.5 to 50 ppm leads to a higher rate of polymerization and a better control over the polymerization reaction. ¹H NMR and GPC analyses as well as chain extension reaction confirmed the very high chain‐end functionality of the resultant polymer. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Copper(0)‐mediated radical copolymerization of vinyl acetate and acrylonitrile in DMSO at ambient temperature

In this work, Cu(0)‐mediated radical copolymerization of vinyl acetate (VAc) and acrylonitrile (AN) was explored. The polymerization was carried out at 25°C with 2,2′‐bipyridine as ligand and dimethyl sulfoxide as solvent. The copolymerization proceeded smoothly producing moderately controlled molecular weights at low VAc feed ratios. The high VAc feed ratios generated low polymerization rate and poorly controlled molecular weights. FTIR, ¹H NMR, and differential scanning calorimetry confirmed the successful obtaining of the copolymers. Based on ¹H NMR spectra, the reactivity ratios of VAc and AN were calculated to be 0.003 and 1.605, respectively. This work conveyed the first example for the Cu(0)‐mediated radical polymerization of AN and VAc, wherein VAc cannot be homopolymerized by Cu(0)‐mediated radical polymerization technique. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Thermal,flexural, and impact strength studies on phenolic novolac resin/acrylonitrile–butadine rubber blends

Phenolic novolac resin was modified with nitrile rubber (NBR) using resol as compatibilizer. These systems were characterized by differential scanning calorimetry, flexural and impact strength. The resin was prepared by varying percentage of NBR. The curing behavior of unmodified and NBR-modified phenolic resin has been studied. The results reveal that the exothermic heat of cure for NBR-modified system increases due to the participation of the double bond of butadiene. In addition, the impact strength and flexural strain increase with increasing percentage of NBR in the phenolic resin matrix.