Anisotropic Conductivity of Diblock Copolymer Films

The first part of this article reviews the orientation of the surface and the in-bulk microdomain structures of diblock copolymers. Well-defined poly(styrene-b-2-vinylpyridine) diblock copolymers (about 50 wt% polystyrene blocks) formed horizontally oriented lamellar microdomains when these copolymers were cast from a nonselective solvent by means of the air–copolymer and substrate–copolymer interactions. The second section reviews the preparation of semiconducting materials by the exposure of these films to alkyl dihalide vapor. This film had an anisotropic conductivity with about 8 orders of magnitude. The third section reviews the construction of ionic complex phases by an ion-exchange reaction of quaternized poly(2-vinylpyridine) (P2VP) layers with lithium perchlorate. Finally, the introduction of colloidal silver into quaternized P2VP layers by reduction of silver iodide is reported. High electrical anisotropy originated in the orientation of microphase-separated structure of diblock copolymer films.     

Core-Shell Type Polymer Microspheres Prepared from Diblock Copolymer Films

In the first part of this article, the preparation method for core-shell type polymer microspheres from diblock copolymer films is reviewed. The core-shell type polymer microspheres were obtained from the crosslinking reaction in spherical microdomains formed by diblock copolymer film. In the second section, the solution and solid properties of core-shell type microspheres are reviewed. The micelle of core-shell type microsphere moved like pseudolatex. Its solubility depended strongly on that of shell segments. Finally, the miscibility behaviors of binary core-shell type microsphere blends are reported briefly.     

Diblock Thin Films with Densely Hexagonally Packed Nanochannels

Films, 2 μm thick, with hexagonally packed and uniformly sized nanochannels with a diameter of ˜17 nm and at a density of ˜5 × 10¹⁰ cm^–2 were prepared. These channels were partially filled with poly(acrylic acid) (PAA) and the structural change of PAA chains with variations in pH, ionic strength, and ion type caused water permeability to change by several orders of magnitude. These membranes with “chemical valves” should be useful in controlled drug release or chemical sensing. In cyclopentane, the PAA chains probably collapse onto the channel walls and the channel centers should open up. The channels allowed the separation of species according to their difference in size and this property should be useful for future studies of polymer chain reptation through the nanochannels.     

Thermal Conductivity in Nanocrystalline Ceria Thin Films

The thermal conductivity of nanocrystalline ceria films grown by unbalanced magnetron sputtering is determined as a function of temperature using laser‐based modulated thermoreflectance. The films exhibit significantly reduced conductivity compared with stoichiometric bulk CeO₂. A variety of microstructure imaging techniques including X‐ray diffraction, scanning and transmission electron microscopy, X‐ray photoelectron analysis, and electron energy loss spectroscopy indicate that the thermal conductivity is influenced by grain boundaries, dislocations, and oxygen vacancies. The temperature dependence of the thermal conductivity is analyzed using an analytical solution of the Boltzmann transport equation. The conclusion of this study is that oxygen vacancies pose a smaller impediment to thermal transport when they segregate along grain boundaries.     

PEO-b-PS两亲性嵌段共聚物的合成与表征

以PEO-Br为大分子引发剂,CuBr/2-2’-联吡啶为催化体系,采用原子转移自由基聚合(ATRP)方法制得了一系列分子量可控且分子量分布窄的两亲性嵌段共聚物,通过1H-NMR、GPC、DSC等测试手段对其进行了表征,研究结果表明嵌段共聚物随着聚氧乙烯含量的降低,结晶度(Xc)、结晶熔融温度(Tm)、结晶温度(Tc)降低;当共聚物中聚氧乙烯的含量降为45%时,嵌段共聚物已无结晶现象。     

Chemical Interactions and Their Role in the Microphase Separation of Block Copolymer Thin Films

The thermodynamics of self-assembling systems are discussed in terms of the chemical interactions and the intermolecular forces between species. It is clear that there are both theoretical and practical limitations on the dimensions and the structural regularity of these systems. These considerations are made with reference to the microphase separation that occurs in block copolymer (BCP) systems. BCP systems self-assemble via a thermodynamic driven process where chemical dis-affinity between the blocks driving them part is balanced by a restorative force deriving from the chemical bond between the blocks. These systems are attracting much interest because of their possible role in nanoelectronic fabrication. This form of self-assembly can obtain highly regular nanopatterns in certain circumstances where the orientation and alignment of chemically distinct blocks can be guided through molecular interactions between the polymer and the surrounding interfaces. However, for this to be possible, great care must be taken to properly engineer the interactions between the surfaces and the polymer blocks. The optimum methods of structure directing are chemical pre-patterning (defining regions on the substrate of different chemistry) and graphoepitaxy (topographical alignment) but both centre on generating alignment through favourable chemical interactions. As in all self-assembling systems, the problems of defect formation must be considered and the origin of defects in these systems is explored. It is argued that in these nanostructures equilibrium defects are relatively few and largely originate from kinetic effects arising during film growth. Many defects also arise from the confinement of the systems when they are ‘directed’ by topography. The potential applications of these materials in electronics are discussed.     

Effects of Thermal Annealing on the Structure of Ferroelectric Thin Films

The effects of thermal annealing on the structure of polycrystalline Pb(Zr_0.3Ti_0.7)O₃ (PZT) ferroelectric thin films prepared by chemical solution deposition on Pt/TiO _x electrode stacks were studied using scanning electron microscopy, transmission electron microscopy (TEM), and grazing incidence X-ray specular and diffuse reflectivity of synchrotron radiation. The stratified multilayered structure and element diffusions in the sample were characterized by TEM. Global statistical structural parameters including the density, surface or interface roughness and thickness of each layer in the samples were obtained from fitting the X-ray specular reflectivity using a homogeneous stratified multilayer model of PZT/Pt/TiO _x /SiO₂. The results showed that the PZT surface and PZT/Pt interface roughness changed slightly during thermal annealing in oxygen at 700°C. By contrast, the density increase of the PZT ceramic and density decrease of the Pt-bottom electrode during annealing were observed. A high density value of the PZT ceramic film after the annealing was found, up to 99.8% of the theoretical value of the corresponding bulk ceramics. The density changes of the PZT and Pt layers were further confirmed by X-ray diffuse reflectivity. The influences of the annealing treatment on the density changes of the PZT and Pt layers were attributed to the further densification of the PZT ceramic and incorporation of light elements such as Zr, Ti and O from the neighboring layers into the Pt layer, respectively, as discussed in correlation with the TEM analyses.     

Dispersion and Consolidation of Alumina Using a Bis-Hydrophilic Diblock Copolymer

A water-soluble diblock copolymer, poly[(methacrylic acid)- b -(ethylene oxide)], has been used to formulate alumina slurries that are dispersed over a wide range of pH through a combination of electrostatic and steric repulsion. The anionic poly(methacrylic acid) block, a short chain ( M _W∼700 g/mol), interacts with the amphoteric alumina surface at pH 3 and acts as an anchor block. The nonionic poly(ethylene oxide) (PEO) block ( M _W= 3000 g/mol) only appears to have a steric functionality. At high pH, the polymer coated surface has a net negative charge due to the excess negative sites associated with the highly dissociated methacrylic acid (MAA) units; this provides electrostatic repulsion at, for example, pH 9, which is the isoelectric point for pure alumina. The PEO chains extend from the surface and stabilize the alumina particles between pH 5 to 9 via an entropy-driven, steric repulsion. The PEO chains provide the dominating dispersive force at low pH, where very little electrostatic repulsion is possible because the positive surface charge of alumina has been neutralized by the negative sites of the adsorbed polyacid. On consolidation through pressure filtration at low pressures (2 to 5 MPa), the saturated, consolidated bodies formulated at pH 5 have a relative density of ∼0.56. These consolidated bodies initially exhibit a flow stress, but then fluidize after an extended strain (up to 0.5). The fluidization phenomenon is believed to be due to the unraveling of the PEO chains that appear to entangle between adjacent particles during consolidation. The unraveling was directly observed with an atomic force microscope between two BaTiO₃ surfaces coated with the same diblock copolymer used for the alumina powder.     

Towards Understanding the Chemical Structure Modification of EVA Copolymer upon MAPLE Processing of Thin Films

A series of coatings from poly(ethylene-co-vinyl acetate) (EVA) were obtained using the matrix-assisted pulsed laser evaporation (MAPLE) technique. By changing the process parameters, i.e., laser fluence and EVA co-polymer concentration in the target, coatings with various morphologies and topographies were produced. The evaluation of the film structure was based on an analysis of optical and atomic force microscopy and profilometry measurements. A detailed chemical structure investigation, conducted based on Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) spectra, revealed that although the general structure was preserved, some alterations of ethylene (Et) and vinyl acetate (VAc) blocks took place. The most noticeable change was in the ester group that was transformed into ketone and carboxyl groups; nevertheless, some changes in the aliphatic main chain were also present. The chemical structure changes in EVA coatings took place regardless of the process parameters used. The use of chloroform as a solvent to dissolve the EVA copolymer was indicated as a possible reason of the changes as well as the tendency of EVA macromolecules to form clusters. Nevertheless, due to low level of structure alteration, it has been shown that the MAPLE technique can be successfully used to obtain coatings from polymers with more complex structures, which are soluble in a limited number of solvents.     

ATRP法合成两亲性聚乙二醇-聚丙烯酸叔丁酯嵌段共聚物

以mPEG-Br为大分子引发剂,CuBr/PMDETA为催化体系,采用原子转移自由基聚合法(ATRP)合成了两亲性嵌段共聚物聚乙二醇-聚丙烯酸叔丁酯(mPEG-b-PtBA),并采用FT-IR,1H-NMR和GPC等表征了聚合物的结构.考察了单体与引发剂的配比、反应时间、反应温度及催化剂与配体的比例等因素对产物的分子量...     

硅烷薄膜

制备了一种涂膜．其特征为：涂膜由含至少—个活性基团选自卤素原子、烷氧基和异氰酸酯基的硅烷化合物形成。涂膜分子部分通过硅、锗、锡、钛和锆元素中的至少一种以共价键方式附着于底材表面，部分相互聚合。涂膜透明．膜厚1nm-0．5μm，膜至少可以通过5次耐磨试验．方法为采用1：1的糖和酱油的混合物．在300℃下加热20min．然后冷却．烘干并粘附的污迹可以用湿布手工擦拭除去。     

Thermal Expansion and Thermal Expansion Anisotropy of SiC Polytypes

The principal axial coefficients of thermal expansion for the (3C), (4H), and (6H) polytypes of SiC are considered to identify the structural role of the stacking layer sequence as it affects the thermal expansion. A general equation based on the fractions of cubic and hexagonal layer stacking is developed that expresses the principal axial thermal expansion coefficients of all of the SiC polytypes. It is then applied to address the thermal expansion anisotropy of the noncubic SiC structures.     

热处理对BiO_x薄膜的组成和结构的影响

采用反应磁控溅射法在氧气和氩气比例为20∶100的混合气体中制备了非化学计量的氧化铋薄膜。薄膜分别在真空和空气中400℃退火30min。采用X射线光电子能谱(XPS)和X射线衍射(XRD)研究了薄膜在真空和空气中退火对其组成和结构的影响。分析表明,在真空退火条件下薄膜中的金属铋和次氧化铋发生了相变,金属铋晶粒长大;而在空气中退火时薄膜主要发生了金属铋和次氧化铋的氧化过程,得到了四方Bi2O3。     

Chemical and Structural Evolution of Sol-Gel-Derived Hydroxyapatite Thin Films under Rapid Thermal Processing

Chemical and structural evolution of hydroxyapatite thin films produced by sol-gel synthesis is characterized by ion beam analysis, X-ray diffraction, and Fourier transform infrared spectroscopy. Formation of the hydroxyapatite structure began at 500°C; no other phases were observed at higher temperatures. Elimination of residual organics was observed in the form of the disappearance of excess oxygen, hydrogen and carbon. Crystal size increases with increasing anneal temperature; spectroscopy indicates the formation of highly crystalline films. The analytical methods chosen provide insight into subtle chemical and structural changes which occur in films produced by this synthetic route.     

Synthesis and Characterization of a Novel Diblock Copolymer with a Polyrotoxane Block

A novel diblock copolymer with a polyrotaxane block α-cyclodextrins-poly (ε-caprolactone)-b-poly{2,5-bis[(4-methoxypheny)oxycabony]-styrene} (α-CD-PCL-b-PMPCS) was successfully synthesized by combining ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP). The diblock copolymer was confirmed by ¹H NMR, GPC and solid-state ¹³C CP/MAS NMR spectroscopic analysis. Its phase structures and phase transitions were investigated by thermogravimetric analyses and wide-angle X-ray diffraction (WAXD). WAXD and solid-state ¹³C CP/MAS NMR spectroscopic study confirmed that inclusion complexes domains of the polyrotaxanes assumed a channel-type structure.     

Fabrication of Regularly Patterned Microporous Films by Self‐Organization of an Amphiphilic Liquid‐Crystalline Diblock Copolymer in a Dry Environment

An amphiphilic LCBC PEO‐b‐PAz consisting of flexible PEO as a hydrophilic block and poly(methacrylic acid) containing an azobenzene moiety in side chain as a hydrophobic LC segment was synthesized and used to fabricated microporous films by spin‐coating method under a dry environment. With the help of a small amount of water, well‐arranged ellipsoidal micropores embedded in a LC matrix were obtained and the pore size is in the range of several tens µm of water. The influence of water content and rotational speed was studied in detail. It was found that regularly patterned microporous films can be prepared with certain water content, and the pore size can be easily tailored through changing the rotational speed. The obtained microporous structures showed good thermal and photo stability.

     

Fabrication of Highly Ordered Polymeric Nanodot and Nanowire Arrays Templated by Supramolecular Assembly Block Copolymer Nanoporous Thin Films

Realizing the vast technological potential of patternable block copolymers requires both the precise controlling of the orientation and long-range ordering, which is still a challenging topic so far. Recently, we have demonstrated that ordered nanoporous thin film can be fabricated from a simple supramolecular assembly approach. Here we will extend this approach and provide a general route to fabricate large areas of highly ordered polymeric nanodot and nanowire arrays. We revealed that under a mixture solvent annealing atmosphere, a near-defect-free nanoporous thin film over large areas can be achieved. Under the direction of interpolymer hydrogen bonding and capillary action of nanopores, this ordered porous nanotemplate can be properly filled with phenolic resin precursor, followed by curation and pyrolysis at middle temperature to remove the nanotemplate, a perfect ordered polymer nanodot arrays replication was obtained. The orientation of the supramolecular assembly thin films can be readily re-aligned parallel to the substrate upon exposure to chloroform vapor, so this facile nanotemplate replica method can be further extend to generate large areas of polymeric nanowire arrays. Thus, we achieved a successful sub-30 nm patterns nanotemplates transfer methodology for fabricating polymeric nanopattern arrays with highly ordered structure and tunable morphologies.     

LiMn2O4薄膜的快速退火制备及其性质

为了获得电化学性能优良的锂离子薄膜电池正极材料,采用快速退火技术制备L iMn2O4薄膜,用X射线衍射、扫描电子显微镜检测和分析了薄膜的物相及表面形貌;用循环伏安、恒流充放电研究了L iMn2O4薄膜的电化学性质。结果表明,制备的L iMn2O4薄膜均匀、致密、无龟裂;在退火温度从700℃升高到850℃的过程中,薄膜容量从34μAh/(cm2.μm)逐步升高到40μAh/(cm2.μm);当退火时间从1 m in延长到4 m in时,薄膜容量由36μAh/(cm2.μm)升高到41μAh/(cm2.μm),但当退火时间进一步延长到8 m in时,薄膜容量下降到39.5μAh/(cm2.μm);对于不同温度退火2 m in制备的薄膜而言,800℃退火得到的L iMn2O4薄膜经100次循环后的每次容量损失为0.021%,循环性能最好;对于750℃不同退火时间制备的L iMn2O4薄膜来说,退火时间为4 m in时得到的薄膜循环性能最好,经100次循环后每次容量损失仅为0.025%,表明快速退火制备的L iMn2O4薄膜具有优良的循环性能。     

含固体颗粒嵌段共聚高分子熔体微相结构的Monte Carlo模拟

采用改进的键长涨落空穴扩散算法,在立方格子上对含固体颗粒的两嵌段共聚高分子熔体的微相结构进行了Monte Carlo(MC)模拟. 重点考察了固体颗粒的大小、固体颗粒与嵌段共聚高分子的选择性作用、共聚高分子链的组成fA等因素对熔体微相结构的影响. 模拟结果表明,固体颗粒与高分子链节有选择性吸附作用时不利于形成层状相,而倾向于形成柱状或网络状结构;适当大小的惰性固体颗粒(与高分子链嵌段的长度相当)有利于系统形成层状相结构;无论系统是否含有固体颗粒,嵌段共聚高分子的对称程度增加都有利于形成层状结构.     

铁电薄膜的微图形化研究

铁电薄膜在微电子和光电子技术中有着重要的或潜在的应用,可以制作随机存取存储器,热释电阵列探测器,铁民微电子机械系统等,在这些器件的制作过程中,铁电薄膜的微图形化是非常重要的一环,本文简要介绍了几种重要的铁电薄膜微图形化方法及有关研究结果,并比较了这些方法的优缺点。