Study of the formation of self-assembled monolayers on nitinol

Shape memory alloys such as nitinol (NiTi) have gained interest due to their unique and unusual properties of thermal shape memory, superelasticity, and good damping properties. Nitinol is mainly used for medical purposes. In order to control the surface properties of this alloy, self-assembled monolayers (SAMs) were formed and characterized on the native oxide surface of nitinol for the first time. Factors which affect the formation of SAMs, such as head group functionality, chain length, and tail group functionality, were varied and analyzed. Functionalized alkyl phosphonic acid molecules (OH, COOH, and CH3) formed monolayers on the nitinol surface using a simple deposition method resulting in the molecules being ordered and strongly bound to the surface. Diffuse reflectance infrared spectroscopy (DRIFT), contact angle goniometry, atomic force microscopy (AFM), and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) were used to characterize the surfaces before and after organic modification.     

单分散聚苯乙烯微球的表面皱纹化

首先制备了不同粒径的未交联的单分散聚苯乙烯(PS)微球;而后通过离子溅射技术在PS微球表面沉积了一层均匀光滑的铂(Pt)壳层,得到了PS-Pt核壳结构的复合微球;最后借用溶剂溶胀法诱导微球表面起皱的发生,从而制备了表面带有皱纹微结构形貌的PS微球.系统考察了微球表面Pt层厚度(t)、微球粒径(D)、溶剂组成(即溶胀度)等因素对球面起皱和皱纹形貌的影响,获得了球面皱纹周期与Pt层厚度的指数关系;结合理论分析了其起皱行为,实验结果与理论分析相吻合.此外,将表面起皱与表面等离子体刻蚀技术相结合,实现了表面带有纳米点状凸起与皱纹复合微结构形貌的PS微球的可控制备.     

含酞菁功能基聚苯乙烯的光电导性能研究

合成了新型含酞菁功能基聚苯乙烯，该聚合物具有优良的溶解性能和成膜能力，同时又有一定的光电导性，对该聚合物的染料增感研究发现结晶紫，孔雀绿对于该聚合物均有增感作用，较大幅度地提高了光电导性．采用ＥＳＲ和荧光光谱的研究表明，该聚合物的光电导机理可能是形成了电荷转移络合物．     

聚苯乙烯提取物的检测与评价

随着材料科学的迅速发展,聚合物材料以不同的形态越来越广泛地应用于食品包装中。但是由于聚合物材料自身的特性及其改性加工,导致了很多低分子量化合物的形成,因而给食品安全性带来很大隐患,也危害着人们的身体健康。为了解决这一问题,在选用材料前,必须分析聚合物材料中低分子化合物的迁移情况,考虑迁移过程对包材使用的影响。实验中选用正庚烷、8%乙醇、50%乙醇和蒸馏水作为食品模拟液,用气相色谱测定聚苯乙烯提取物的迁移量,进而将实验数据分析比较。结果显示,迁移量随着温度的升高和时间的延长而不断增加,溶剂种类的影响为:正庚烷>50%乙醇>8%乙醇>蒸馏水。     

Preferential Interactions on Polystyrene Divinylbenzene Copolymeric Sorbents

The adsorption of picric acid, naphthalene-sulfonic acid, and toluenesulfonic acid onto a polystyrene divinylbenzene copolymeric sorbent in methanol-water systems at 25°C was studied by reverse-phase high performance liquid chromatography. The observed peak asymmetry and increase in capacity factor at high methanol concentrations in the mixture was attributed to preferential interactions of the solutes at the surface. The phenomena were not as pronounced for octadecyl silane bonded phases.     

预发泡聚苯乙烯颗粒改性研究进展

介绍了当前预发泡聚苯乙烯颗粒(EPS)的各种改性研究方法,其中包括各种赋予发泡颗粒某种特殊功能的改性方法:无卤阻燃、低吸油型、低吸水型、耐化学药剂型、高抗冲性能型、含低挥发性有机气体(VOC)的环保型预发泡聚苯乙烯颗粒,以及涉及的各种改性工艺,包括先将聚苯乙烯材料改性后再造粒的二步法改性工艺、聚合成粒过程中的一步法改性工艺、聚苯乙烯颗粒发泡前的表面改性和颗粒发泡后再进行表面改性等方法,并提出了改性过程中的注意事项和影响最终产品力学性能的主要原因。     

Diffusion Studies on Polystyrene in 1,4-Dioxane

The diffusion behavior of polystyrene with narrow molecular weight distribution at 20℃ in 1, 4-dioxane was investigated by the photon correlation spectroscopy. The cumulant method was employed for the analysis of the intensity-intensity autocorrelation function measured over a wide range of the scattering vector. The diffusion coefficient D was determined as the function of concentration C in the molecular weight range of 3. 0×104-1. 20×106. In a low concentration range, D was found to be linearly dependent on C, which has been found for some other systems. The dependence of D on molecular weight at infinite dilution can be written as an empirical formula D0 = kDM-γ M, the exponent γ(0. 576 ±0. 01) is in good agreement with the result of the scaling theory.     

Simulation of growth and corrosion during the formation of a passive layer

From the analysis of experiments relative to the formation of a passive layer at the Li-solvent interface a model is proposed in order to describe the gross features concerning the growth of this layer. In this model the growth is initiated by chemical reactions partially counterbalanced by a poisoning process. The model which works at a mesoscopic scale is simulated on a two-dimensional lattice. A quantitative analysis of the results shows that this model appears as the superposition of the Eden model which describes the structure of the front and a similar percolation process which determines the properties of the bulk part of the layer as its porosity. A second model in which the corrosion is taken into account is introduced. It is analyzed in a very simple case in which there is no poisoning. The corrosion induces a restructuring in the layer and this gives rise to a porosity in the bulk part of the layer. Some unexpected results are interpreted.     

氧化铝水合物在聚苯乙烯上的覆盖

由两种或两种以上化合物组成的复合化合物均匀胶体位于制备越来越受到人们的重视[1-7]．作为复合粒子制备方法之一的覆盖技术，人们关注的多是一种无机化合物（金属，氧化物或盐）或有机物在另一种无机化合物上以壳状形式的沉积[3-7]，很少涉及在有机化合物或聚合物上覆盖问题[     

聚苯乙烯修饰碳纳米管表面的研究

利用原子转移自由基聚合方法合成了端基具有一个卤素的聚苯乙烯, 并通过叠氮化反应得到端基为叠氮基团的聚苯乙烯. 利用叠氮基与单壁或复壁碳纳米管的反应， 将聚苯乙烯接到碳纳米管的表面上, 实现了碳纳米管的化学修饰. 通过FTIR, XPS, TEM, UV和Raman光谱等技术证明了聚苯乙烯以共价键形式结合到碳纳米管表面上. 利用TGA估算出连接在碳纳米管上的聚苯乙烯的含量, 并推测出复壁碳纳米管中较多的结构缺陷更有利于聚合物的接枝.     

Polystyrene nanocomposites based on quinolinium and pyridinium surfactants

In this paper pyridine and quinoline-containing salts were employed to modify montmorillonite. TGA analysis shows that the quinolinium modified clay has a higher thermal stability than the pyridinium modified clay. Polystyrene nanocomposites were prepared by in situ bulk polymerisation and direct melt blending using both clays. The X-ray diffraction and transmission electron microscopy results show the formation of intercalated structures. The 50% degradation temperature of the nanocomposites is increased and so is the amount of char from TGA analysis compared to the virgin polymer. Cone calorimetric results indicate that clay reduces the peak heat release rate and average mass loss rate and thus lowers the flammability of the polymer.     

在空心聚苯乙烯微球表面电沉积Au-Cu双壳层

PS/Au/Cu双壳层核壳复合微球是在自制的电沉积装置中首先在空心聚苯乙烯微球模板上电沉积金形成PS/Au微球,然后再电沉积Cu。首先,PS/Au微球保持了较好的球形度,其中沉积层Au粗糙度低,且厚度达到5.6 μm。由于Au和铜有相同的面心立方晶体结构,所以Cu沿着Au的晶体结构在PS/Au表面沉积。微球断面Au-Cu结合非常紧致,Cu的厚度为8.62 μm,Au的厚度为4.04 μm。PS/Au/Cu微球和Au-Cu双壳层的形貌、厚度,成分和粗糙度是通过3D体式显微镜,SEM、EDS和XRD表征,其结果显示PS/Au/Cu微球及双壳层Au-Cu均匀细致,粗糙度低。     

链缠结对等规聚苯乙烯结晶的影响

在1×10^－3～2×10^－5 g•mL^－1溶液浓度范围内, 用溶液雾化冷冻升华法制备了等规聚苯乙烯(i-PS)的单链、寡链非晶态聚集体. 随着溶液浓度降低, i-PS分子链团间的分离程度增大, 链间缠结随之减少, 因此冷冻升华制备的样品中单、寡链线团数目逐渐增多. DSC研究结果表明随着溶液浓度的降低, 冷冻升华样品的结晶温度逐渐降低; 等温结晶得到的晶粒熔点和结晶度降低. 由浓度为2×10^－5 g•mL^－1溶液制备的i-PS样品在468.3 K熔体结晶60 min后, 得到平均体积约为1.5×10⁴ nm³的单链晶粒. 用SEM观察到晶粒尺寸约为20～50 nm. 采用偏光显微镜(POM)测量了不同温度等温时i-PS单、寡链聚集体球晶的生长速率. 用Hoffmann理论进行了描述, 计算得到了i-PS单链聚集体熔体结晶片晶的端表面能(σ_e)为30.2 erg•cm^－2, 侧表面能(σ)为5.7 erg•cm^－2及单分子链折叠功(q)约为4.5×10^－13 erg•molecule^－1. 与文献值相比, 实验结果表明链缠结对聚合物结晶有很大影响.     

Blends Based on Polystyrene and Statistical Aromatic Copolycarbonates

The compatibility of polystyrene (PS) with aromatic copolycarbonates containing bisphenol A (BPA) and tetramethyl bisphenol A (TMBPA) was investigated. The simple prevision scheme developed by Sonja Krause was employed to evaluate the effect of the copolymer molecular structure on the miscibility with polystyrene. These prevision data were used to select copolycarbonates of potential interest. Statistical copolycarbonates (CPC) containing different BPA/TMBPA molar ratios were synthesised by polycondensation reaction between a mixture of the two monomers and phosgene. PS/polycarbonates blends, prepared by casting from chloroform solution, were studied with differential scanning calorimetry and optical microscopy to evaluate the components compatibility, which increases with the TMBPA copolymer content.     

在空心聚苯乙烯微球表面电沉积Au-Cu双壳层

PS/Au/Cu双壳层核壳复合微球是在自制的电沉积装置中首先在空心聚苯乙烯微球模板上电沉积金形成PS/Au微球,然后再电沉积Cu。首先,PS/Au微球保持了较好的球形度,其中沉积层Au粗糙度低,且厚度达到5.6 μm。由于Au和铜有相同的面心立方晶体结构,所以Cu沿着Au的晶体结构在PS/Au表面沉积。微球断面Au-Cu结合非常紧致,Cu的厚度为8.62 μm,Au的厚度为4.04 μm。PS/Au/Cu微球和Au-Cu双壳层的形貌、厚度,成分和粗糙度是通过3D体式显微镜,SEM、EDS和XRD表征,其结果显示PS/Au/Cu微球及双壳层Au-Cu均匀细致,粗糙度低。     

聚苯乙烯微球表面接枝丙烯腈的研究

采用分散聚合法制备出平均粒径为3.85 μm的窄分布聚苯乙烯微球， 并在此基础上引入第二单体丙烯腈进行共聚反应， 制备出平均粒径为4.02 μm的窄分布苯乙烯-丙烯腈共聚物微球. 对聚苯乙烯微球和苯乙烯-丙烯腈共聚物微球进行了形貌及粒径、红外光谱、差示扫描量热法(DSC)分析， 结果表明丙烯腈基团均匀分布在聚苯乙烯微球表面， 提高了聚苯乙烯微球表面的极性.     

Studies on Mechanism of Grafting of Polystyrene on Elastomer Backbone

The mechanism of grafting of polystyrene on a polybutadiene (PB) backbone during the preparation of impact-resistant polystyrene was studied by withdrawing samples during propolym-erization from beginning of the reaction to about 25% conversion. Good separation of the “elastomer and graft” fraction of the polymer from the free polystyrene part could be achieved by using 0.24 volume fraction of methanol in (MEK + benzene) + methanol solvent-nonsolvent. IR analysis of the grafted fraction showed that the microstructure of the elastomer remained unaltered. The unsaturation of the samples studied through the bromine number as well as by the perbenzoic acid number was also found to remain unchanged. Formation of free polystyrene started with the onset of polymerization and was faster. During prepolymerization, 80% of styrene converted constantly to form free polystyrene and 20% went into the grafted polymer. The results indicate that grafting is initiated through proton abstraction at the α-carbon of butadiene, most probably by initiator radicals. The grafted polystyrene chains possibly are shorter than free polystyrene chains.     

利用等离子体技术研究聚苯乙烯表面的接枝聚合反应

用O₂等离子体对聚苯乙烯(PS)进行预处理, 再用Ar等离子体引发N-乙烯基吡咯烷酮(NVP)在其表面接枝聚合. 通过接触角(CA)及表面自由能(SE)分析, 探讨了O₂等离子体预处理条件对PS表面自由能的影响, 确定了预处理的最佳条件. 通过衰减全反射红外光谱(ATR-FTIR)、X射线光电子能谱(XPS)和动态接触角(DCA)分析, 比较了O₂等离子体预处理前后和接枝聚合前后PS的表面组成及表面性能, 实验结果表明, 利用等离子体技术能成功地将NVP接枝聚合于PS表面, 接枝聚合后的PS表面由于极性高分子链和粗糙度的增加, 亲水性增强, 水滴易在其表面铺展. 由于接枝聚合后PS表面的高分子链在水中发生重构, 使后退角降低幅度较大, 接触角滞后现象明显.     

Novel Supports for Ethylene Polymerisation Based on Polystyrene Polymers

The industrial use of metallocene/methylaluminoxane catalytic systems and late transition metal catalysts requires the use of supports to directly get polyethylene (PE) with spherical morphology. The presence of residues of the inorganic support gives rise to PE contamination problems, therefore less contaminating organic supports may present an interesting alternative. In this work, linear hydroxypolystyrene (PS-OH) and polystyrene-block-isoprene copolymer (PS-b-PI) were tested as supports for ethylene polymerisation. The ability of these polymers when dissolved in a selective solvent to form micelles or aggregates, was investigated by light scattering techniques. Next, their capacity to act as MAO or TMA-activated supports towards MeDIP(2,6-iPrPh₂FeCl₂) catalyst was analysed by carrying ethylene polymerisation tests and PE morphology studies. The PS-b-PI copolymer, used as organic support in heptane, enabled the obtention of PE with well defined spherical morphology.