时间-电位法跟踪磷化过程及温度对磷化成膜的影响

目前对磷化成膜机理及规律的认识受限于测试手段等因素,影响了工艺开发和理论探讨。在工业铁皮表面磷化成膜,采用电化学方法,通过开路电位-时间曲线,原位跟踪了磷化成膜过程,用X射线衍射仪(XRD)对磷化过程不同阶段的磷化膜成分进行了测试、分析;通过动电位极化曲线、硫酸铜点滴试验和扫描电镜(SEM)等研究了温度对磷化成膜的影响;讨论了磷化成膜的电化学机理。研究表明:开路电位-时间曲线中的反应斜率、成膜时间等是研究磷化成膜过程的重要特征参数;温度对低常温磷化成膜过程和膜层的耐蚀性能有显著影响,推荐铁基体低常温磷化以35~45℃为佳。     

相转化条件对纤维素膜结构与性能的影响及机理

采用相转化法制备纤维素膜,通过考察转化成膜的条件——成膜液的种类、浓度、黏度,凝固浴浓度、温度等对纤维素膜结构和性能的影响,深入研究了纤维素膜的相转化成膜机理。研究表明,天然植物纤维素成膜过程依赖于扩散动力学,相平衡的浓度差。成膜液中的溶剂与凝固液非溶剂的扩散速度很大程度上决定了膜的结构和性能。成膜液自身的种类、浓度以及凝固液的条件也都会影响成膜后的结构与性能。     

天然纤维深化处理后物化性能的研究

研究了纤维素的溶解性和成膜性,并对不同的温度和压力对纤维素的溶解性及成膜性的影响进行探讨,通过天然纤维蒸煮液直接提取物成膜实验和深化处理后提取成膜物质的实验等2种方法,表明天然纤维可以成膜.     

柠檬酸钠在常温磷化中的作用

传统的亚硝酸盐磷化促进剂不符合清洁生产的发展需要,为此,通过X射线衍射、极化曲线、扫描电镜方法研究了柠檬酸钠作为促进剂对常温磷化的成膜时间、成膜厚度、磷化膜的表面状态及耐蚀性等的影响.结果表明,柠檬酸钠含量在0.5～2.5g/L时能有效增加磷化膜的厚度,成膜均匀致密,膜层耐腐蚀性能最佳.     

水性金属防护涂料的研究进展

从金属表面过渡层技术、自分层技术及高性能水性成膜聚合物的合成、水性涂料成膜过程研究等方面，论述了水性金属涂料领域存在的问题、所取得的进展及发展趋势。     

酞菁类化合物有机光电导材料的成膜方式

为制备较高光电导性的酞菁有机复合膜，本文简要分析了影响其光电导性的主要因素，针对酞菁类化合物难溶性和成膜困难，对这类有机光电导材料的成膜方式进行了概述，着重探讨了分散于聚合物成膜材料中涂覆成膜、LB膜，蒸发镀膜及悬挂酞菁环衍生物的可溶性聚合物成膜等工艺过程中遇到的某些关键性技术问题，并提出了对这类光电导材料进一步研究的部分建议。     

苯丁光致抗蚀干膜的改性

讨论了用丙烯酸酯改性的成膜树脂组分及各组分的相对比例、溶剂、分子量调节剂、加料方式等对成膜树脂分子量及干膜性能的影响。试验结果表明改性改善了市售苯丁抗蚀干膜的性能。     

非晶型磷化成膜技术的研究

就非晶型磷化成膜技术的工艺方法、膜层的理化性能、质量控制因素等作了必要的论述，并对成膜机理进行了有益的探讨。本技术已经获得了工业上的实际应用，受到了越来越多的用户的欢迎。     

一种纳米TiO2薄膜负载技术及性能研究

以硅溶胶为成膜粘结剂、高分子聚乙烯醇为成膜助剂,采用粘结成膜法制备纳米TiO2薄膜,考察了所制得薄膜的光催化性能、耐热性、耐腐蚀性等宏观性能以及耐老化性能.实验结果表明,该纳米薄膜对液相和气相甲醛光降解5h,降解率分别达87%和93%以上;其耐热性、耐水性、耐腐蚀性和界面粘结性能优异;耐老化性能优异,对提高基材的抗老化性能有明显的作用.     

乙酸钠浓度对AZ91D镁合金锡酸盐转化膜的影响

镁合金的无铬化学转化处理已成为其防护技术研究的一个重要方向,为此,开发了一种以乙酸钠为主要成分的镁合金锡酸盐转化工艺,采用全浸腐蚀试验、扫描电镜(SEM)、X射线衍射(XRD)等方法研究了AZ91D镁合金在含不同乙酸钠浓度成膜液中所形成膜层的结构,并比较了膜层的耐腐蚀性能.结果表明:成膜过程中,随着成膜液中乙酸钠浓度的...     

Nanoparticle Regrowth Enhances Photoacoustic Signals of Semiconducting Macromolecular Probe for In Vivo Imaging

Smart molecular probes that emit deep‐tissue penetrating photoacoustic (PA) signals responsive to the target of interest are imperative to understand disease pathology and develop innovative therapeutics. This study reports a self‐assembly approach to develop semiconducting macromolecular activatable probe for in vivo imaging of reactive oxygen species (ROS). This probe comprises a near‐infrared absorbing phthalocyanine core and four poly(ethylene glycol) (PEG) arms linked by ROS‐responsive self‐immolative segments. Such an amphiphilic macromolecular structure allows it to undergo an ROS‐specific cleavage process to release hydrophilic PEG and enhance the hydrophobicity of the nanosystem. Consequently, the residual phthalocyanine component self‐assembles and regrows into large nanoparticles, leading to ROS‐enhanced PA signals. The small size of the intact macromolecular probe is beneficial to penetrate into the tumor tissue of living mice, while the ROS‐activated regrowth of nanoparticles prolongs the retention along with enhanced PA signals, permitting imaging of ROS during chemotherapy. This study thus capitalizes on stimuli‐controlled self‐assembly of macromolecules in conjunction with enhanced heat transfer in large nanoparticles for the development of smart molecular probes for PA imaging.     

On‐Chip Chemical Self‐Assembly of Semiconducting Single‐Walled Carbon Nanotubes (SWNTs): Toward Robust and Scale Invariant SWNTs Transistors

In this paper, the fabrication of carbon nanotubes field effect transistors by chemical self‐assembly of semiconducting single walled carbon nanotubes (s‐SWNTs) on prepatterned substrates is demonstrated. Polyfluorenes derivatives have been demonstrated to be effective in selecting s‐SWNTs from raw mixtures. In this work the authors functionalized the polymer with side chains containing thiols, to obtain chemical self‐assembly of the selected s‐SWNTs on substrates with prepatterned gold electrodes. The authors show that the full side functionalization of the conjugated polymer with thiol groups partially disrupts the s‐SWNTs selection, with the presence of metallic tubes in the dispersion. However, the authors determine that the selectivity can be recovered either by tuning the number of thiol groups in the polymer, or by modulating the polymer/SWNTs proportions. As demonstrated by optical and electrical measurements, the polymer containing 2.5% of thiol groups gives the best s‐SWNT purity. Field‐effect transistors with various channel lengths, using networks of SWNTs and individual tubes, are fabricated by direct chemical self‐assembly of the SWNTs/thiolated‐polyfluorenes on substrates with lithographically defined electrodes. The network devices show superior performance (mobility up to 24 cm² V^?1 s^?1), while SWNTs devices based on individual tubes show an unprecedented (100%) yield for working devices. Importantly, the SWNTs assembled by mean of the thiol groups are stably anchored to the substrate and are resistant to external perturbation as sonication in organic solvents.     

New Concepts and Applications in the Macromolecular Chemistry of Fullerenes

A new classification on the different types of fullerene‐containing polymers is presented according to their different properties and applications they exhibit in a variety of fields. Because of their interest and novelty, water‐soluble and biodegradable C₆₀‐polymers are discussed first, followed by polyfullerene‐based membranes where unprecedented supramolecular structures are presented. Next are compounds that involve hybrid materials formed from fullerenes and other components such as silica, DNA, and carbon nanotubes (CNTs) where the most recent advances have been achieved. A most relevant topic is still that of C₆₀‐based donor‐acceptor (D–A) polymers. Since their application in photovoltaics D–A polymers are among the most realistic applications of fullerenes in the so‐called molecular electronics. The most relevant aspects in these covalently connected fullerene/polymer hybrids as well as new concepts to improve energy conversion efficiencies are presented. The last topics disccused relate to supramolecular aspects that are in involved in C₆₀‐polymer systems and in the self‐assembly of C₆₀‐macromolecular structures, which open a new scenario for organizing, by means of non‐covalent interactions, new supramolecular structures at the nano‐ and micrometric scale, in which the combination of the hydrofobicity of fullerenes with the versatility of the noncovalent chemistry afford new and spectacular superstructures.     

Vesicles and Liposomes: A Self‐Assembly Principle Beyond Lipids

This Progress Report describes the latest advances in vesicles and liposomes. Recent work on the self‐assembly of complex polymer systems shows that the formation of polymer vesicles or closed hull structures is archetypal, leading to fascinating new possibilities and applications in materials science. A general view of the underlying self‐assembly mechanisms leading to vesicles and the control of size, shape, and other vesicular properties by physicochemical means is presented, as background. This is followed by an overview of the recently described new classes of polymer and supramolecular tectons that make vesicle formation a more general phenomenon going beyond just lipids. Finally, the potential applications of vesicles, including non‐lipid vesicles, are outlined.     

Molecular Self‐Assembly on Graphene

The formation of ordered arrays of molecules via self‐assembly is a rapid, scalable route towards the realization of nanoscale architectures with tailored properties. In recent years, graphene has emerged as an appealing substrate for molecular self‐assembly in two dimensions. Here, the first five years of progress in supramolecular organization on graphene are reviewed. The self‐assembly process can vary depending on the type of graphene employed: epitaxial graphene, grown in situ on a metal surface, and non‐epitaxial graphene, transferred onto an arbitrary substrate, can have different effects on the final structure. On epitaxial graphene, the process is sensitive to the interaction between the graphene and the substrate on which it is grown. In the case of graphene that strongly interacts with its substrate, such as graphene/Ru(0001), the inhomogeneous adsorption landscape of the graphene moiré superlattice provides a unique opportunity for guiding molecular organization, since molecules experience spatially constrained diffusion and adsorption. On weaker‐interacting epitaxial graphene films, and on non‐epitaxial graphene transferred onto a host substrate, self‐assembly leads to films similar to those obtained on graphite surfaces. The efficacy of a graphene layer for facilitating planar adsorption of aromatic molecules has been repeatedly demonstrated, indicating that it can be used to direct molecular adsorption, and therefore carrier transport, in a certain orientation, and suggesting that the use of transferred graphene may allow for predictible molecular self‐assembly on a wide range of surfaces.     

大分子自组装体系及自组装功能膜结构的研究

本文主要介绍了３种大分子自组装体系，含硫化合物的在重金属表面的自组装功能膜、聚合物在溶液状态下的自组装体系和聚合物基材上的自组装功能膜。文中还介绍了表征自组分析方法，着重介绍了用于自组装功能膜表面、界面结构分析的两种，红外光谱法和原子力显微镜。     

Substrate Templating upon Self‐Assembly of Hydrogen‐Bonded Molecular Networks on an Insulating Surface

Molecular self‐assembly on insulating surfaces, despite being highly relvant to many applications, generally suffers from the weak molecule–surface interactions present on dielectric surfaces, especially when benchmarked against metallic substrates. Therefore, to fully exploit the potential of molecular self‐assembly, increasing the influence of the substrate constitutes an essential prerequisite. Upon deposition of terephthalic acid and trimesic acid onto the natural cleavage plane of calcite, extended hydrogen‐bonded networks are formed, which wet the substrate. The observed structural complexity matches the variety realized on metal surfaces. A detailed analysis of the molecular structures observed on calcite reveals a significant influence of the underlying substrate, clearly indicating a substantial templating effect of the surface on the resulting molecular networks. This work demonstrates that choosing suitable molecule/substrate systems allows for tuning the balance between intermolecular and molecule–surface interactions even in the case of typically weakly interacting insulating surfaces. This study, thus, provides a strategy for deliberately exploiting substrate templating to increase the structural variety in molecular self‐assembly on a bulk insulator at room temperature.     

Orientation of polymer functionalized nanorods in thin films

A directed self assembly of anisotropic nanostructures offers a possibility to provide unique functional materials, which are e.g., important in optoelectronic devices. We use the liquid crystalline behavior of polymer functionalized TiO2 and ZnO nanorods to apply methods well known for low molecular liquid crystals to achieve oriented thin films. Convective forces in the meniscus on a structured substrate obtain thin layers of oriented nanoparticles with a ordering parameter of S = 0.7. As another method we present the orientation of polystyrene covered ZnO nanorods under an applied electric field. The method offers a perpendicular alignment of the rods to the surface.     

Bioinspired Superhydrophobic Highly Transmissive Films for Optical Applications

Inspired by the transparent hair layer on water plants Salvinia and Pistia, superhydrophobic flexible thin films, applicable as transparent coatings for optoelectronic devices, are introduced. Thin polymeric nanofur films are fabricated using a highly scalable hot pulling technique, in which heated sandblasted steel plates are used to create a dense layer of nano‐ and microhairs surrounding microcavities on a polymer surface. The superhydrophobic nanofur surface exhibits water contact angles of 166 ± 6°, sliding angles below 6°, and is self‐cleaning against various contaminants. Additionally, subjecting thin nanofur to argon plasma reverses its surface wettability to hydrophilic and underwater superoleophobic. Thin nanofur films are transparent and demonstrate reflection values of less than 4% for wavelengths ranging from 300 to 800 nm when attached to a polymer substrate. Moreover, used as translucent self‐standing film, the nanofur exhibits transmission values above 85% and high forward scattering. The potential of thin nanofur films for extracting substrate modes from organic light emitting diodes is tested and a relative increase of the luminous efficacy of above 10% is observed. Finally, thin nanofur is optically coupled to a multicrystalline silicon solar cell, resulting in a relative gain of 5.8% in photogenerated current compared to a bare photovoltaic device.     

Hydrogen‐Bonded Molecular Networks of Melamine and Cyanuric Acid on Thin Films of NaCl on Au(111)

Self‐assembly of organized molecular structures on insulators is technologically very relevant, but in general rather challenging to achieve due to the comparatively weak molecule–substrate interactions. Here the self‐assembly of a bimolecular hydrogen‐bonded network formed by melamine (M) and cyanuric acid (CA) on ultrathin NaCl films grown on a Au(111) surface is reported. Using scanning tunneling microscopy under ultrahigh‐vacuum conditions it is demonstrated that it is possible to exploit strong intermolecular forces in the M–CA system, resulting from complementary triple hydrogen bonds, to grow 2D bimolecular networks on an ultrathin NaCl film that are stable at a relatively high temperature of ≈160 K and at a coverage below saturation of the first molecular monolayer. These hydrogen‐bonded structures on NaCl are identical to the self‐assembled structures observed for the M–CA system on Au(111), which indicates that the molecular self‐assembly is not significantly affected by the isolating NaCl substrate.