聚异丙基丙烯酰胺接枝聚丙烯膜表面接触角温敏性“黏滑”行为研究

固体表面尤其是温敏性表面的湿润行为对其实际应用具有重要的影响, 本文报道了聚异丙基丙烯酰胺(PNIPAM)接枝聚丙烯微孔膜表面水接触角的温敏性“黏滑”现象. 扫描电镜被用于表征接枝膜表面的形貌变化, 发现在PNIPAM的低临界共溶温度(LCST)以上膜表面接枝层突起较为明显. 水接触角实验表明未改性聚丙烯膜表面的前进角和后退角行为正常, 且随温度无明显变化, 而PNIPAM接枝膜在LCST以上则出现了“黏滑”现象(stick-slip). “黏滑”行为产生的主要原因可能是在LCST以上PNIPAM链的收缩使得膜表面出现能垒, 因而造成液滴三相线的“黏滑”.     

Materials Studio软件在“金属”教学中的应用*

以中学化学所涉及的“金属”物质教学内容为例,运用MS分子模拟软件内嵌的Visualizer,Build 及Symmetry property 等3个功能模块,在不同尺度(从埃、纳米、微米到厘米)范围内,实现对“金属原子结构”“金属晶体”及“金属性质(密度)”的连续性可视化展示,帮助学生从原子的视角深入理解化学物质微观结构与宏观性质之间的本质相关性。     

硅胶表面上脂肪酸蒸气吸附膜

应用Gibbs方程由甲酸、乙酸和丙酸蒸气在硅胶上的吸附等温线计算了吸附膜的表面压力(π)与每个吸附分子所占面积(σ)间的关系(π～σ图).所得曲线与不溶物在溶液表面上的结果相似,均表现出有“液态扩张膜”“转变膜”和“液态凝聚膜”.不同的是,不溶物只能形成单分子层膜,而硅胶表面上的脂肪酸吸附膜则是多分子层的.蒸气吸附膜由单层向多层的转变,恰与π～σ图上的“液态扩张膜”向“转变膜”的转变相对应.吸附焓(△H)与吸附熵(△S)的计算结果表明,在此转变附近AH和AS发生急剧变化.     

静电纺丝制备多级结构TiO2微纳米纤维

通过对共轴电纺内流体溶液浓度和流速的调控得到4种具有不同内部结构的TiO₂微纳米纤维, 即具有“微孔”、“囊泡”、“竹节”和“管”状结构的TiO₂微纳米纤维, 实现了对纤维内部结构的有效控制, 对于新型仿生中空纤维的研究具有重要意义.     

一次性聚苯乙烯发泡塑料餐具解禁事件及其对化学教学的启示

“一次性聚苯乙烯发泡塑料餐具”在禁用14年之后,近期被国家发展和改革委员会“解禁”,并引起社会的广泛关注和争论。“一次性发泡塑料餐具”问题也是化学教学中经常涉及的“热点”问题之一,因此“解禁”事件也必然会影响到化学教学。结合“一次性发泡塑料餐具”生产的化学工艺流程,分析了其“解禁”原因,探讨了“解禁”事件对化学教学的几点启示。     

在解密“骗局”中推广化学科普知识*

“骗局”中也蕴含着丰富的化学知识。高校科普工作者可以在解密这些“骗局”中,推广化学科普知识。围绕5W 模式--“谁来科普”“要科普给谁”“如何科普”“科普什么”和“科普效果如何”等5个问题,尝试建立一种在解密“骗局”中推广化学科普知识的新思路。具体为:以青少年和老年人为重点科普对象,构建“老师+学生”共同实施、现场演示与讲解并重、新旧媒体联合传播、“效果指标体系”评价的科普模式,实现精准化学科普的目的。     

基于认识化学正向价值的教学实践——以“二氧化碳*”为例

模拟大型科普求真类节目《是真的吗？》创设学习氛围;通过基于生活生产实际的“日常灭火可否用N₂代替CO₂”“深海捕获CO₂可否调控温室效应”“石油采矿业中,向油井下注射1吨CO₂可否增产原油3~5吨”“用石灰水可否保鲜鸡蛋”等4个核心问题及3个真假难辨的小问题,引导学生从化学的正向视角深刻认识二氧化碳的性质;利用移动磁贴板设计板书,引导学生经历并建构结构化知识体系。     

从纳米晶到三维超晶格结构

纳米晶的有序组装对未来纳米材料的应用拓展具有重要意义. 本综述介绍了纳米晶三维超晶格的研究价值以及制备方法,着重对“胶体溶液蒸发”、“不良溶剂扩散”、“胶束引导集聚”、“氢键连接”、“静电聚集”、“DNA导向”、“外场辅助”和“水－油界面辅助”的组装机制进行了总结与评述,同时也探讨了这一新兴领域中仍然存在的挑战.     

基于文献分析的“氧化还原反应”概念教学逻辑

以15篇有关“氧化还原反应”的课例研究文献为研究对象,基于内容分析法归纳出4种主要的教学逻辑：“分类标准直给型”“分类标准批判型”“反应本质揭示型”“知识演绎批判型”。从“知识是什么”“知识是如何被理解的”2个维度对4种教学逻辑进行评析,以反思氧化还原反应教学研究的发展及其局限。     

大学有机化学“五维度”教学新策略——以“芳烃的亲电取代和亲核取代反应”为例

介绍了大学有机化学“强理念、重思维、活课堂、共育人、乐钻研”五维度教学新策略的内涵与实践。以线下教学为主,腾讯会议和慕课为辅助,践行“有机化学是科学也是艺术”的教学理念;采用多循环“疑探式”教学方式,辨析亲电试剂和亲核试剂的多样性;注重培养学生多种科学思维的综合运用;强化“文献预习”“练习讲解”“综合作业”“师生互动”等多个教学环节,加深学生对知识的理解与应用,提升学生在课堂中的参与度,着重培养学生的科学思维和人文素养、自主学习与团队合作精神。     

Modification of aqueous polyurethanes by forming latex interpenetrating polymer networks with polystyrene

A series of latex particles with interpenetrating polymer network structure have been synthesized from waterborne polyurethane (PU) and polystyrene (PS). The effect of PU/PS composition, cross-linking density in the PS domain as well as in PU have been studied in terms of dispersion size, transmission electron microscopy morphology, mechanical and dynamic mechanical properties in addition to swellability in water and toluene of the dispersion cast film. It was found that inverted core (PS)–shell (PU) morphology was well defined and that the domain size as well as the film properties were well controlled by the latex composition and cross-linking density of both phases. Received: 15 March 2000 Accepted: 21 February 2001     

Composite thin films of poly(phenylene oxide)/poly(styrene) and PPO/silver via vapor phase deposition

We report fabrication of thin (100～300 nm) poly(phenylene oxide) (PPO) films and their composites with poly (styrene) (PS) and silver (Ag) nanoparticles using a one‐step electron beam‐assisted vapor phase co‐deposition technique. Surface morphology and the structure of the deposited polymer thin film composites were characterized by FTIR, Raman, X‐ray spectroscopy, and contact angle measurements. As‐deposited PPO films and PPO/Ag composites were of porous nature and contrary to solvent casting techniques were free from nodular growth. In the case of PPO/PS thin film polymer composites, however, film morphology displayed nodular growth of PPO with nodule diameters of about ～200 nm and height of approximately 50 nm. Unique morphological changes on the porous PPO thin film surface were noticed at different Ag filling ratios. Further, the capacitance of PPO/Ag composites (<16 wt%) were measured under radio‐frequency conditions and they were functional up to 100 MHz with an average capacitance density of about 2 nF/cm². The fabricated PPO‐based composite systems are discussed for their potential applications including embedded capacitor technology. Copyright © 2008 John Wiley & Sons, Ltd.     

静电喷涂法制备具有低吸附力的超疏水性聚苯乙烯膜

采用聚苯乙烯的N,N-二甲基甲酰胺溶液为原料, 通过静电喷涂的方法制备了具有微-纳米复合结构的聚苯乙烯膜. 通过调节溶液浓度, 得到了不同的结构、浸润性及吸附性的表面. 当聚苯乙烯的质量分数为5%、分子量为25000时, 得到的表面与水的接触角达到167°, 吸附力达到15 μN, 表明该膜表面具有超疏水性的同时对水滴具有很低的吸附力. 此外, 分子量的大小也对静电喷涂膜表面形貌的变化起重要的作用.     

Polystyrene with different topologies: Study of the glass transition temperature in confined geometry of thin films

The glass transition behaviour of polystyrene (PS) with systematically varied topologies (linear, star-like and hyperbranched) confined in nanoscalic films was studied by means of spectroscopic vis-ellipsometry. All applied PS samples showed no or only a marginal depression in glass transition temperature T_g in the order hyperbranched PS (5 K) > star-like PS (3 K) > linear PS (0 K) for the thinnest films analyzed. The T_g behaviour was accompanied by the observation of the film density in dependence of film thickness. A maximum decreased density of about 7% for hyperbranched PS and 5% for star-like PS and again no deviation in density of bulk was found for linear PS. Accordingly, we deduce from these results considering an experimental accuracy of about ± 2 K for T_g and up to ±3% for film density, that the polymer topology only barely influences T_g in the confinement of thin films.     

Contact angle of water on polystyrene thin films: effects of CO(2) environment and film thickness

We examine the contact angle of water droplets on polystyrene (PS) thin films of varying thicknesses supported by silicon wafers under both air and pressurized carbon dioxide (CO2) environments. At 23 degrees C, the contact angle is found to increase upon increasing CO2 pressure in the vapor regime and then levels off in the liquid CO2 regime. A macroscopic model based on Young's equation and the geometric-mean method for interfacial tensions, and long-range van der Waals interactions, correctly predicts the trends and the magnitude of the contact angle dependence on pressure, although deviations occur at high CO2 activities. The contact angle was also found to depend on film thickness, h, when h was comparable to or smaller than 50 nm. Specifically, the contact angle decreases with decreasing PS film thickness. This behavior could be accounted for with the use of a model that incorporates the effects of film thickness, CO2 pressure, and the long-range van der Waals potential.     

Photochemical fabrication of a well-defined diblock copolymer nanotemplate using 172-nm vacuum ultraviolet light

Well-ordered nanopore arrays were successfully prepared from polystyrene (PS) and poly(methyl methacrylate) (PMMA) diblock copolymer (DBC) film based on a photochemical approach using 172-nm vacuum ultraviolet (VUV) light. Since the etching selectivity between the PS and PMMA domains against activated oxygen species generated by the VUV irradiation of atmospheric oxygen molecules was markedly different, PMMA was preferentially decomposed, resulting in the formation of PS nanopore arrays. Both the photoetching rate and final morphology depended greatly on the atmospheric pressure during VUV irradiation. Since at 10 Pa the PS domains degraded less due to the shortage of oxygen molecules in the atmosphere, the residual matrix kept its fine nanostructures up to 40 min of irradiation. The matrix could be eliminated completely when irradiation was extended to 60 min at this pressure. On the other hand, at 10(3) Pa the DBC film was removed completely from the substrate within 10 min of irradiation. However, at 10(3) Pa, not only the decomposition of the PMMA domains, but also the photoetching rate of the PS domains accelerated significantly resulting in marked distortion of the generated nanostructures. By selecting an appropriate atmospheric pressure and time for VUV irradiation, we were able to control both nanoarray formation and elimination without the use of any physical and/or chemical treatment.     

Ring-shaped morphology in solution-cast polystyrene-poly(methyl methacrylate) block copolymer thin films

We report observation of ring-shaped morphology formed in thin films of a cylinder-forming polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer cast from 1,1,2,2-tetrachloroethane (Tetra-CE) solution via relatively fast solvent evaporation rates, in which Tetra-CE is a good solvent for both blocks but preferential affinity for the minority PMMA block. We studied the microstructure of a set of solution-cast block copolymer films dried with different solvent evaporation rates, R. The control with different R leads to keeping microstructures in different solution concentrations (phi) and bringing mechanical strain fields with different strength in the film, for which faster evaporation rates result in microstructures of lower solution concentrations and mechanical strain fields of higher strength. As R decreases from rapid evaporation (approximately 0.1 mL/h), the film microstructure evolved from an intermediate ringlike morphology sequentially to ring-shaped morphologies including loose and tight rings and then inverted phase of PS spheres in a PMMA matrix and finally reached the equilibrium phase, namely, cylinders of PMMA in a PS matrix. In view of the influence of the film constraints, the microstructure of a film with a terraced free surface profile has been examined. The results indicate that the ring-shaped morphology can form as long as the film thickness is larger than a critical value of about one microdomain spacing. In the case where the film thickness is larger than that value, the nature of solvent and the kinetics of solvent evaporation are shown to be mainly responsible for the ring-shaped morphology formation.     

Ordered porous ZnO thin films formed by dip-coating method using PS templates

Monolayer polystyrene spheres (∼400 nm) array templates were assembled orderly on clean glass substrates by dip-coating method from emulsion of polystyrene (PS). Porous ZnO thin films were also prepared by dip-coating method to fill the interstices among the close-packed PS templates with ZnO and annealing to remove the PS templates. Results showed that ZnO sol concentration and dipping time of PS templates in sol had great influences on the morphology of ordered porous ZnO thin films. There was a shrinkage ratio of about 30% from pore to PS. SEM observation showed that the PS array templates had face-centered cubic close-packing. X-ray diffraction (XRD) spectra showed the porous ZnO thin film was wurtzite structure. The optical transmittance decreased with decreasing wavelength of lights, but was kept above 80% beyond the wavelength of 550 nm. Optical band-gap of the porous ZnO thin film annealed at 500°C was 3.22 eV.     

Blends of poly(epsilon-caprolactone) and intermediate molar mass polystyrene as Langmuir films at the air/water interface

Poly(epsilon-caprolactone)/polystyrene (PCL/PS) blends, where nonamphiphilic PS is glassy in the bulk state at the experimental temperature of 22.5 degrees C, are immiscible as Langmuir films at the air/water (A/W) interface. Surface pressure-area per monomer isotherm analyses indicate that the surface concentration of amphiphilic PCL is the only factor influencing the surface pressure below the collapse transition. For PS-rich blends, Brewster angle microscopy (BAM) studies at the A/W interface and atomic force microscopy studies on Langmuir-Schaefer films reveal that PS nanoparticle aggregates formed at very low surface pressures can form networks upon further compression. The morphologies seen in PS-rich blends (networklike rings) are consistent with a recent study of a nonamphiphilic polyhedral oligomeric silsesquioxane (POSS), octaisobutyl-POSS, blended with amphiphilic poly(dimethylsiloxane), suggesting that the nonamphiphilic PS aggregates at the A/W interface produce domains with dipole densities that differ from that of pure PCL. In all composition regimes, the amphiphilic PCL phase tends to spread and form a continuous surface layer at the A/W interface, while simultaneously improving the dispersion of nonamphiphilic PS domains. During film expansion, BAM images show a gradual change in the surface morphology from highly continuous networklike structures (PS-rich blends) to broken ringlike structures (intermediate composition) to small discontinuous aggregates (PCL-rich blends). This study provides valuable information on the morphological evolution of semicrystalline PCL-based polymer blends confined in a "two-dimensional" geometry at the A/W interface and fundamental insight into the influence of microstructure (domain size, phase-separated structures, crystalline morphology, etc.) on the interfacial properties of blends as Langmuir films.     

Polystyrene-block-poly(ethylene oxide) stars as surface films at the air/water interface

Star diblock copolymers containing polystyrene (PS) and poly(ethylene oxide) (PEO) were investigated as surface films at the air/water interface. Both classic and dendritic-like stars were prepared containing either a PS core and PEO corona or the reverse. The investigated polymers, consisting of systematic variations in architectures and compositions, were spread at the air/water interface, generating reproducible surface pressure-area isotherms. All of the films could be compressed to higher pressures than would be possible for pure PEO. For stars containing 20% or more PEO, three distinct regions appeared. At higher areas, the PEO absorbs in pancakelike structures at the interface with PS globules sitting atop. Upon compression, a pseudoplateau transition region appeared. Both regions strongly depended on PEO composition. The pancake area and the pseudoplateau width and pressure increased in a linear fashion with an increasing amount of PEO. In addition, minimum limits of PEO chain length and mass percentage were determined for observing a pseudoplateau. At small areas, the film proved less compressible, producing a rigid film in which PS dominated. Here, the film area increased with both molecular weight and the amount of PS. Comparison with pure linear PS showed the stars spread more, occupying greater areas. Among the stars, the PEO-core stars were more compact while the PS-core stars spread more. The influence of architecture in terms of the core/corona polymers and branching were also examined. The effects of architecture were subtle, proving less important than PEO chain length or mass percentage.