Self-assembly of C60 containing poly(methyl methacrylate) in ethyl acetate/decalin mixtures solvent

[60]Fullerene (C₆₀) was mono-substituted with well-defined poly(methyl methacrylate) (PMMA-b-C₆₀) using the atom transfer radical polymerization (ATRP) technique. The self-assembly behaviors of PMMA-b-C₆₀ in ethyl acetate (EA) and decalin mixtures were studied using laser light scattering (LLS) and transmission electron microscopy (TEM). Homogeneous solutions of PMMA-b-C₆₀ can be obtained in the solvent mixtures containing more than 40 wt% EA, where the molar ratio of decalin to EA is close to 1. For each solvent mixture, unimers coexist with micelles and large aggregates. The sizes of PMMA-b-C₆₀ micelles and aggregates are independent of polymer concentration, confirming that they are produced via the closed association mechanism. For the various solvent mixtures, the weight-averaged molecular weights, M_w of the PMMA-b-C₆₀ aggregates range from 4.1×10⁷ to 12.5×10⁷ g/mol. The hydrodynamic radii of the large aggregate, R_h, vary from 90 to 136 nm, while the z-averaged radii of gyration, R_g, range from 210 to 311 nm. The R_g/R_h value for each solvent mixture is ∼2.3, which is independent of decalin contents in the mixed solvents. The morphological study using the transmission electron microscope suggests that the large aggregates are composed of porous large compound micelles (LCM) in solution.     

Durable antimicrobial treatment of cotton fabrics using N‐(2‐hydroxy)propyl‐3‐trimethylammonium chitosan chloride and polycarboxylic acids

N‐(2‐hydroxy)propyl‐3‐trimethylammonium chitosan chloride (HTCC), a water‐soluble chitosan quaternary ammonium derivative, was used as an antimicrobial agent for cotton fabrics. HTCC has a lower minimum inhibition concentration (MIC) against Staphylococcus aureus, Klebsiella pneumoniae, and Escherichia coli compared to that of chitosan; however, the imparted antimicrobial activity is lost on laundering. Thus crosslinking agents were utilized to obtain a durable antimicrobial treatment by immobilizing HTCC. Several crosslinkers such as dimethyloldihydroxyethylene urea (DMDHEU), butanetetracarboxylic acid (BTCA), and citric acid (CA) were used with HTCC to improve the laundering durability of HTCC treatment by covalent bond formation between the crosslinker, HTCC and cellulose. The polycarboxylic acid treatment was superior to the DMDHEU treatment in terms of prolonged antimicrobial activity of the treated cotton after successive laundering. Also, the cotton treated with HTCC and BTCA showed improved durable press properties without excessive deterioration in mechanical strength or whiteness when compared to the citric acid treatment. With the addition of only 0.1% HTCC to BTCA solutions, the treated fabrics showed durable antimicrobial activity up to 20 laundering cycles. The wrinkle recovery angle and strength retention of the treated fabrics were not adversely affected with the addition of HTCC. Therefore, BTCA can be used with HTCC in one bath to impart durability of antimicrobial activity along with durable press properties to cotton fabric. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1567–1572, 2003     

Preparation and characterizations of interpenetrating polymer network hydrogels of poly(ethylene oxide) and poly(methyl methacrylate)

Interpenetrating polymer network (IPN) hydrogels based on poly(ethylene oxide) and poly(methyl methacrylate) were prepared by radical polymerization using 2,2‐dimethyl‐2‐phenylacetophenone and ethylene glycol dimethacrylate as initiators and crosslinkers, respectively. The IPN hydrogels were analyzed for sorption behavior at 25°C and at a relative humidity of 95% using dynamic vapor sorption. The IPN hydrogels exhibited a relatively high equilibrium water content in the range of 13–68%. The state of water in the swollen IPN hydrogels was investigated using differential scanning calorimetry. The free water in the hydrogels increased as the hydrophilic content increased. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 258–262, 2003     

Study on the thermoplastic vulcanizate using ultrasonically treated rubber powder

Nowadays, waste EPDM (ethylene propylene diene monomer) increasingly has been causing significant environmental problems with increasing numbers of vehicles. From the perspective of the environment and economics, recycling is the best method to treat waste materials. This study investigated waste EPDM/PP (polypropylene) blends with waste EPDM. Waste EPDM powders were treated ultrasonically, which physically modifies the rubber particles to confer good mechanical properties. Also investigated were the relevance of the mass percentage of the dispersed phase, the influence of the geometry and rotation speeds of the screw used in extrusion, and the melting temperature of PP materials on the morphology and mechanical properties of the blend. The purpose of this study was to develop a valuable thermoplastic elastomer from waste EPDM. This study concentrated on determining the optimum conditions for producing a blend by extrusion, including parameters of screw geometry, screw rotational speed, and operating temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2503–2507, 2003     

略论亚里士多德的正义观

亚里士多德的正义观,既是古希腊社会历史发展的理论表现,也是对此前古希腊政治思想的继承和发展。亚里士多德政治正义观的价值基础是社会公共利益,其理论的核心是法治,在治国策略上坚持中庸之道是适用于一切政体的公理。     

"再听证"条款考疑

介绍了日本、韩国及我国台湾地区的行政程序法关于再次举行听证会的规定.分析了我国行政程序法试拟稿及部分地方立法中有关于再听证规定存在的问题,并提出了具体的修改意见.     

大跨度钢桁拱桥节点疲劳性能试验研究

重庆朝天门大桥是当今世界第一大跨度拱桥,其下弦节点直接承受公路荷载与轻轨荷载的双重作用,下弦节点连接处应力幅大,目前大跨度钢桥中未曾有类似的设计及试验,因此,该文对其下弦节点连接进行了高周疲劳试验以确定其连接的可靠性。首先通过相关规范及朝天门大桥的交通量确定出模型的试验荷载,并完成从实桥节点到模型的转换,然后对模型进行正常设计荷载下的200万次疲劳试验,该试验验证了设计寿命期内朝天门大桥节点连接的安全性,并用空间有限元分析结果验证了试验数据的真实性。最后进行了该模型的疲劳破坏试验,得出了这类节点的疲劳破坏规律,为该类桥梁以后的设计及监测提供了数据及参考意见。     

钢管塔架K型加肋节点的承载力分析

通过试验对1／4加肋K型钢管插板连接节点的极限承载力进行了研究,同时借助有限元分析了主管壁厚,环板宽度和厚度以及不同加肋方式对节点极限承载力的影响。在此基础上根据试验和有限元结果以及节点的破坏模式提出了适用于估算此类节点极限承载力的极限分析模型和建议公式。结果表明：加肋K型钢管插板连接节点的承载力受主管壁厚和环板宽度和厚度的影响较大,且分主管控制和环板控制2种情况来讨论。采用的四铰破坏机理和五铰破坏机理极限分析模型能较好的反映此类节点的受力性能。     

基于可控电抗器的单调谐滤波器的两种控制方法比较

可控电抗器作为电力设备中常用的一种非线性装置,其控制方式直接影响设备的整体性能.本文从可控电抗器的控制特性出发,阐述了基于可控电抗器的单调谐滤波器的两种控制方法,即相位跟踪控制法和自寻最优控制法.比较了两种方法在110V工作电压下的控制效果及各自的应用环境.     

开放系统中基于历史角色的快速协商模型

在开放式网络环境中,资源的请求者和提供者往往隶属于不同的安全域。在陌生人之间建立信任并保证共享资源的安全可以通过自动信任协商来实现。如何加速这些实体之间的后续协商过程是随之要解决的重要问题。通过分析自动信任协商对系统的需求,提出了支持快速协商的基于历史角色的自动信任协商模型HRFN。HRFN将角色的概念引进来,根据协商过程中暴露出的证书为协商对方分配一定的角色,并将这些角色记录在历史信息记录中,同时记录该角色对应的证书暴露序列。在后续协商过程中,如果资源请求者的历史角色具有访问权限,则双方根据该角色对应的证书暴露序列来暴露证书。经试验验证,HRFN模型的安全性能更高,而且满足自动信任协商的快速需求。