表面活性剂CTAB水溶液中的T2弛豫分散研究

用CPMG脉冲序列测定了表面活性剂十六烷基三甲基溴化铵（CTAB）分子中的氮甲基(N-CH₃)质子的横向弛豫时间（T₂表观）,并发现测得的T₂表观\}与序列中的重聚脉冲间隔时间的一半τ _cp有关,说明存在横向弛豫分散现象. 当在τ_cp≤1 ms时,T₂表观与τ²_cp}呈线性关系;而当τ_cp≥4.6 ms时,T₂表观变得与τ_cp无关. 利用Luz-Meiboom两体化学交换模型计算了不同浓度的CTAB溶液中的N-CH₃质子的本征横向弛豫时间（T₂本征）和化学交换速率k_ex,发现k_ex与T₂本征和自扩散系数D一样,在临界胶束浓度（CMC）附近发生突变. 这个突变反映了CTAB分子在从单体到胶束的转变过程中其动力学特性发生了改变.      

用1H NMR研究正丁醇对PEO-PPO-PEO嵌段共聚物胶团形成的影响

采用¹H NMR波谱技术研究了正丁醇对PEO-PPO-PEO嵌段共聚物温度依赖的胶团化过程影响. 实验结果表明,正丁醇的加入急剧地降低嵌段共聚物的临界胶团温度（CMT）. 化学位移变化表明正丁醇烷基端与嵌段共聚物PPO链段之间的疏水相互作用是导致嵌段共聚物CMT降低的主要原因. 选择性激发ROE实验进一步证实,在形成的嵌段共聚物-正丁醇混合胶团中,正丁醇的烷基链段进入胶团内核而正丁醇的羟基端则处于胶团外壳一侧.     

PEO-PPO-PEO嵌段共聚物与没食子酸丙酯的相互作用研究

PEO-PPO-PEO嵌段共聚物在水溶液中能够形成稳定的胶团结构,可作为疏水药物的有效载体[1]。然而,PEO-PPO-PEO与疏水药物在分子水平的作用机理尚未清楚,本工作以没食子酸丙酯(PG)为模型分子,采用动态光散射和核磁共振技术研究了其与嵌段共聚物P123之间的相互作用。研究发现,P123在水溶液中的临界胶团温度(CMT)随PG浓度增加而降低,且较高浓度的PG还能引起P123胶团尺寸的增加。PG烷基链与PPO嵌段甲基间存在较强疏水作用,该作用能促进PPO嵌段的去水化过程,从而降低P123在水溶液中的临界胶团温度(CMT)。此外,PG的酚羟基与嵌段共聚物PEO和PPO嵌段醚氧原子间均存在氢键作用。     

荧光探针法研究N-月桂酰基-N''-羟乙基乙二胺乙酸盐的微极性

用荧光光谱法测定Ⅳ-月桂酰基-Ⅳ'-羟乙基乙二胺乙酸盐(两性乙酸钠)的微极性.芘的荧光强度随着两性乙酸钠浓度的增加而减小,其第一峰(I1)和第三峰(I3)的强度随两性乙酸钠浓度的增加先降低,到达一定浓度后,趋于稳定.由芘的I1/I3与浓度关系可以得出两性乙酸钠的临界胶束浓度(CMC值大约为11.03mmol/L),与表面张力法(1.02mmol/L)测定结果一致.同时研究了无机盐的加入对芘的I1/I3值的影响,无机盐的加人使芘的I1/I3值减小,即无机盐的加入使芘所处的微环境极性减小.     

荧光探针法研究N-月桂酰基-N′-羟乙基乙二胺乙酸盐的微极性

用荧光光谱法测定N-月桂酰基-N′-羟乙基乙二胺乙酸盐(两性乙酸钠)的微极性。芘的荧光强度随着两性乙酸钠浓度的增加而减小,其第一峰(I1)和第三峰(I3)的强度随两性乙酸钠浓度的增加先降低,到达一定浓度后,趋于稳定。由芘的I1/I3与浓度关系可以得出两性乙酸钠的临界胶束浓度(CMC值大约为1.03mmol/L),与表面张力法(1.02mmol/L)测定结果一致。同时研究了无机盐的加入对芘的I1/I3值的影响,无机盐的加入使芘的I1/I3值减小,即无机盐的加入使芘所处的微环境极性减小。     

氧含量对Fe掺杂YBCO体系中载流子局域化与离子团簇效应的影响

对YBa₂Cu_3-xFe_xO_y（x=00，01，02 ）和YBa₂Cu_2.8Fe_0.2O_y（y=705—653 ）系列样品的氧含量、霍尔系数和超导电性进 行了系统的研究.结果表明，氧含量的变化对样品中载流子的输运和转移及超导电性有重要 影响；适当增加氧含量可以减缓Cu(1)位元素替代对超导转变温度T_c的抑制；在 CuO₂面上参与输运的载流子（空穴）浓度是影响样品超导电性的关键因素.从电 荷转移模型出发 ，结合掺杂离子引起的载流子局域化和离子团簇效应，对载流子浓度随掺杂量和氧含量的变 化从微观结构方面进行了讨论.元素替代量的增加或者氧含量的降低（相同替代量的情况下 ）都将导致Cu-O链区的有效氧空位增多，导致替代元素的离子团簇效应和载流子局域化效应 趋于增强，这是引起参与输运的载流子浓度下降，进而导致T_c降低的主要原因. 关键词： 氧含量 霍尔系数 载流子局域化 离子团簇效应     

今日中国物理

 1 北京谱仪开始D_s物理研究据《北京对撞机通讯》报道,目前有关D_s物理测量工作刚刚起步,D_s纯轻子衰变尚未观察到,D_s半轻子衰变与作为参照基准的D_s→（?）π⁺分支比有待精确测定,许多有争议的和未知的D_s轻子道衰变需要进一步研究.北京谱仪D_s的物理目标是:用同理论模型无关的直接测量法,测定D_s⁺→（?）π⁺衰变的绝对分支比;从D_s→ex半轻子衰变的测量,寻找非旁观者胶子过程的贡献:研究D_s→μv,τv纯轻子衰变,测定D_s衰变常数fD_s;有兴趣的D_s强子道衰变的研究.     

我国学者提出粲粒子研究新建议

 据全国粲粒子物理讨论会获悉,中科院学部委员何祚庥以及张肇西,张长春等,对北京谱仪在J/φ能区之外的粲粒子研究提出多项物理建议,包括D_s和D介子（即φ（4160）与φ（3770）衰变产物）、φ（3685）共振态衰变、粲重子与τ轻子性质的研究.（1）φ（3685）共振态衰变与胶子球产生.何祚庥教授计算表明,同J/φ衰变相比,φ共振态衰变中胶子球的产额将增加1.5-3倍.因此,φ可能是胶子球研究的理想能区.φ的许多衰变道有待更精确的测量.     

邻苯二甲酸二甲酯系材料中α-弛豫的降温介电谱测量与分析

对邻苯二甲酸二甲酯(dimethyl phthalate)、邻苯二甲酸二乙酯(diethyl phthalate)、邻苯二甲酸二丁酯(dibutyl phthalate)和邻苯二甲酸二异辛酯 (dioctyl phthalate)系列材料中, α-弛豫的降温介电谱进行了测量, 得出了相应材料α-弛豫的平均弛豫时间τ_α^a 随温度T的变化关系. 通过τ_α^a 的实验结果与经验的Vogel-Fulcher-Tammann)定律τ_α^a = τ_α⁰ exp (A/(T-T₀))的拟合, 获得了上述系列材料的τ_α⁰, A和T₀. 分析发现, 随邻苯二甲酸二甲酯系列分子侧链中碳原子数目n的变化, 材料的τ_α⁰, A, T₀ 和T_g 表现出一定的规律性, 具体为随n的增加, 即分子内部自由度的增多, A和T_g 都表现出近乎相同的先减后再增的趋势, 而1/τ_α⁰ 和T₀ 则表现出基本相同的先快速减小, 然后保持基本上不变的趋势. 关键词： 玻璃化转变 介电谱 α-弛豫')" href="#">α-弛豫 邻苯二甲酸二甲酯系列材料     

正十二烷基硫酸钠在聚丙烯酰胺溶液中聚集的1H NMR研究

利用核磁共振自旋-晶格弛豫时间（T₁）、自旋-自旋弛豫时间（T₂）、自扩散系数（D）以及二维核Overhause增强谱（2D NOESY）技术研究了表面活性剂正十二烷基硫酸钠（SDS）在聚丙烯酰胺（PAM）浓度固定为10 g/L水溶液中的聚集. 结合与SDS水溶液体系核磁共振实验数据比较,得到了如下信息：（1） 当溶液中有PAM存在时,SDS分子的运动性下降,临界聚集浓度提前;（2） 随着SDS浓度的增加,PAM分子的自扩散性能下降,同时分子链的柔软性也下降了;（3） 2D NOESY谱结果表明,PAM与SDS分子间未发生直接的缔合作用.     

Pithecellobium Clypearia Benth Fiber/Recycled Acrylonitrile-Butadiene-Styrene (ABS) Composites Prepared in a Vane Extruder: Analysis of Mechanical Properties and Morphology

The effect of compatibilizer types and concentrations on the mechanical properties and morphology of Pithecellobium Clypearia Benth Fiber (PCBF)/recycled ABS composites prepared by a vane extruder were characterized. In addition, the percentage of compatibilizer was fixed at 8%, and the effect of lubricant concentrations on the mechanical properties and torque behaviors of the composites was also studied. Maleic anhydride grafted ABS (ABS-g-MAH) and maleic anhydride grafted PS (PS-g-MAH) were used as compatibilizers; the lubricant used was Struktol TPW 604 (blend of aliphatic carboxylic acid salts and mono diamides). The composite with 8% ABS-g-MAH showed superior mechanical properties compared to the composite without compatibilizer and the 8% PS-g-MAH compatibilized composites. Compared with PS-g-MAH, ABS-g-MAH was more effective for the composites to improve the interfacial interaction and mechanical properties. The comprehensive mechanical properties of PCBF/recycled ABS composite filled with 4% lubricant were better than the composites without lubricant and the composites with any other content of TPW 604. Moreover, the torque of the composites in an internal mixer decreased with an increasing lubricant content.     

Photodegradation of Decabromo Diphenyl Ether Flame Retardant in Poly (Acrylonitrile Butadiene Styrene) (ABS)

Abstract

Decabromodiphenylether (DBDE) is a brominated flame retardant which belongs to the group of polybromodiphenylethers (PBDEs) often used as a fire resistant additive in various well known polymeric systems like polystyrene, poly(acrylonitrile-butadiene-styrene) (ABS), polypropylene, etc. This compound can be considered as a persistent organic pollutant and presents certain risks for the environment owing to the fact that it is bioaccumulable and not biodegradable. A detailed investigation, described here, was carried out on the effect of ultraviolet/visible radiation on DBDE in ABS with the aim to study the photolytic reactions of this molecule in the solid state, in order to improve the economic and ecological treatment of brominated plastic waste from waste electrical and electronic equipment (WEEE). This study presents new aspects of the photochemical degradation of DBDE/ABS systems in the solid state. The photodegradation of DBDE in ABS was followed by Fourier transform infrared spectroscopy (FTIR) as well as by thermogravimetrical analysis (TGA). Good agreement was obtained for the results of both analytical methods in terms of the overall photolysis of DBDE.     

ABS ternary blends: Morphology,surface gloss,and mechanical properties

ABS/PMMA/PC (acrylonitrile-butadiene-styrene)/poly(methyl methacrylate)/bisphenol A polycarbonate) and ABS/PMMA/phenoxy ternary blends were prepared using a corotating twin-screw extruder, where the ABS content was fixed at 60% by weight, and the other ingredients varied 0 ～ 40%. Tensile modulus, yield strength, elongation at break, and notched impact strength varied linearly with compositions in ABS/PMMA/phenoxy blends, whereas positive synergisms of these properties were generally obtained with ABS/PMMA/PC blends. The results were interpreted in terms of interpositions of PMMA between ABS and PC, which were seen from the TEM micrographs and predicted from the spreading coefficient. Surface gloss of ABS increased in ABS/ PMMA(60/40) blend but decreased in ternary blends, and this phenomenon was possibly explained by the pearl gloss mechanism.     

Morphology and dynamic mechanical properties of poly(acrylonitrile-butadiene-styrene)/polycarbonate/clay nanocomposites prepared by melt mixing

The morphology and dynamic mechanical properties of poly(acrylonitrile-butadienestyrene) (ABS)/polycarbonate (PC)/clay nanocomposites were investigated. From the studies of the transmission electron microscopy (TEM) analysis of the ABS/PC (70/30 wt%) nanocomposites with clay, it was observed that most of the clay existed in the ABS phase and the interface of the ABS and PC. From the studies of the scanning electron microscopy (SEM), droplet size of the PC in the ABS/PC/clay nanocomposites did not change significantly with the clay and has been found to be from 1.0 to 1.5 μm when the clay was added up to 5 phr. The small difference of the droplet size of the PC was maybe due to the similar values of the viscosities of the dispersed phase (PC) and continuous phase (ABS). From the dynamic mechanical properties of the ABS/PC/clay nanocomposites, the storage modulus was increased by the addition of the clay at the rubbery state between 120 and 150°C. From the studies of the tan δ of the ABS/PC/clay nanocomposites, it was shown that double tan δ peaks were observed. The height of the lower temperature tan δpeak was decreased from 4.5 to 3.3 when the clay was increased up to 5 phr. The decrease of the height of the lower tan δ peak in the ABS/PC/clay nanocomposites suggested that the ABS chain motion was restricted by the clay in the ABS phase.     

Effect of an Ultrahigh Rubber ABS Impact Modifier Resin on Mechanical Properties of Intumescent Flame-Retardant ABS Composites

The effect of an ultrahigh rubber acrylonitrile-butadiene-styrene (ABS) impact modifier resin (UHR-ABS) on the mechanical properties of an intumescent flame-retardant ABS composite was characterized. Samples were obtained by compounding ABS and an intumescent flame-retardant master batch that was prepared using an intumescent flame-retardant composite (IFRC) with ABS and/or UHR-ABS as well as by direct compounding IFRC, UHR-ABS, and ABS. The incorporation of UHR-ABS resulted in reduction in the storage modulus, damping behavior and glass transition temperature, as evidenced by dynamic mechanical analysis. With increasing mass fraction of the UHR-ABS, the tensile strength and the flexural strength decreased gradually, and the notched impact strength increased, but the increase was more significant for compounding IFRC, UHR-ABS, and ABS than for compounding ABS and IFRC master batches. SEM micrographs of the fresh fracture surface of the composites were used to estimate the mechanism of the increased notched impact strength owing to the incorporation of UHR-ABS.     

Morphology and Mechanical Properties of Polyamide 6/Acrylonitrile-Butadiene-Styrene Blends Containing Carbon Nanotubes

The blends of polyamide 6/acrylonitrile-butadiene-styrene (PA6/ABS), with added styrene-maleic acid copolymer (SMA) compatibilizer, were prepared through melt mixing in an internal mixer. The effects of blend composition and various process conditions, as well as the addition of multi-wall carbon nanotubes (MWCNTs) to the blends, on the morphology and mechanical properties were investigated. The morphology of the blends and blend nanocomposites were observed by scanning electron microscopy (SEM) and analyzed using an image analysis technique. The mechanical behavior of the blends was investigated by tensile and also impact testing. The results showed that the blend composition as well as the processing conditions significantly affected the morphology and mechanical properties of the PA6/ABS blends. Among the various compositions, the blend with 36?wt.% of ABS and 4?wt.% of SMA compatibilizer exhibited the best mechanical properties. Comparing various speeds and times of mixing, it was found that less mixing speed and longer mixing times resulted in the favorable morphology and conditions for achievement of the desired toughness for the polyamide 6. By adding different amounts of MWCNTs to the blends, it was found that the presence of the carbon nanotubes changed the viscosity of the resulting nanocomposite and thus changed the morphology. These nanocomposites also showed an improvement in mechanical properties. The MWCNTs acted as a second compatibilizer, resulting in a synergistic effect on the mechanical properties of the PA6/ABS blend nanocomposites.     

Catalytic properties of gold nanoparticles immobilized on the surfaces of nanocarriers

Gold nanoparticles are immobilized in the hydrophilic coronas of spherical micelle carriers for high catalytic activity. The micelle is formed by self-assembly of block copolymer, polystyrene-b-poly (acrylic acid), in basic aqueous solution (pH 10) and has a polystyrene core and a poly (acrylic acid) corona. The gold nanoparticles are anchored into the poly (acrylic acid) corona by in situ reduction of the mixture of HAuCl₄ and micelle with NaBH₄. The sizes of the gold nanoparticles can be adjusted by changing the content of the HAuCl₄. In the process of catalyzing p-nitrophenol to p-aminophenol, the reaction shows one-order kinetics, furthermore, the reaction rate increases with the concentration of composites as well as reaction temperature. Comparing the composites with polystyrene as core and poly (4-vinylpyridine)/Au as corona, the catalytic activity of the present composites is higher, which is ascribed to their hydrophilic corona structure.     

Structural and dynamic properties of polyoxyethylene sorbitan monooleate micelle in water dispersion studied by pulsed field gradient NMR

The diffusion phenomenon of a nonionic surfactant, polyoxyethylene sorbitan monooleate (POE-SMO), micelle in aqueous solution was investigated by pulsed field gradient nuclear magnetic resonance (PFG NMR) with a high gradient strength of 17.4 T/m at the diffusion timet _d varied from 3 to 300 ms. This high gradient strength allowed us to measure the slow self-diffusion coefficient of POE-SMO micelle, and the short diffusion time below 10 ms showed the restricted diffusion of the micelle. At the shortt _d the self-diffusion of the micelle was restricted and the restricted sizes were 1.8, 1.5, and 0.8 μm for the POE-SMO concentration of 100, 200 and 300 mM, respectively, and 0.6 μm for the POE-SMO only. The possible reason of this restriction was assumed to be the formation of a spatial network or a micellar clustering. Furthermore, a proton exchange between water molecule and surfactant OH group on the micelle surface was proposed. With respect to this proposal, the residence time of the proton at the micelle surface and the thickness of the surface were investigated from proton self-diffusion coefficients by PFG NMR.     

Effect of Modified Intumescent Flame Retardant via Surfactant/Polyacrylate Latex on Properties of Intumescent Flame Retardant ABS Composites

In order to prepare intumescent flame retardant acrylonitrile-butadiene-styrene (ABS) composites with only a small decrease in their mechanical properties, we investigated the effect of adding an elastomeric polyacrylate latex and the surfactant TX-10 phosphate to modify the ammonium polyphosphate, melamine, and calcium 3-hydroxy-2, 2-bis(hydroxymethyl) propyl phosphate normally used, which resulted in an intumescent flame retardant composite (IFRC) powder with the aim of improving compatibility. These ABS/IFRC composites were compared with standard material containing unmodified intumescent flame retardant (NIFR) by investigating their thermal properties, melt characteristics, mechanical properties, and microstructure. The data showed that the glass transition temperature of the ABS/IFRC composites decreased slightly in all cases, the complex viscosity of the ABS/IFRC composites was remarkably reduced, and the mechanical properties improved in comparison with the material containing NIFR. A slight increase in impact strength retention, as well as a remarkable increase in tensile and flexural strength retention of ABS/IFRC, was achieved due to superior compatibility between ABS and IFRC in comparison with ABS/NIFR.     

Effect of Methyl Methacrylate Graft Acrylonitrile–Butadiene-Styrene on Morphology and Properties of Polycarbonate/Acrylonitrile–Butadiene-Styrene Blend

In order to improve the compatibility of polycarbonate (PC) and acrylonitrile– butadiene–styrene (ABS), a new type of reactive compatibilizer, methyl methacrylate graft acrylonitrile–butadiene–styrene (MABS) tetramer, was synthesized. The structure and properties of PC/ABS (70/30) blend with various MABS ratios were studied in terms of their mechanical and morphological properties. The results indicated that with the addition of MABS, the glass transition temperature (T_g) of the PC and ABS phases were closer to each other. Addition of MABS decreased the domain size of the ABS dispersed phase, making the dispersed phase well distributed, and the interfacial cohesiveness was enhanced. Notched impact strength and elongation at break of the PC/ABS (70/30) blend increased remarkably with the addition of MABS, with a small drop in the tensile strength.