Electroluminescence of a Polymer Film with a Polymer/Polymer Interface

JETP Letters - The effect of a two-dimensional quantum-confined structure formed at a polymer/polymer interface on the radiative recombination of excitons (i.e., electroluminescence) is...     

Photoconductivity along the Polymer/Polymer Interface

Physics of the Solid State - The effect of photoexcitation on the electrical conductivity of the interface between two polydiphenylenephthalide (PDP) polymer films is discovered. It is shown that...     

Dynamics of Polaron at Polymer/Polymer Interface

The migration of a polaron at polymer/polymer interface is believed to be of fundamental importance for the transport and light-emitting properties of conjugated polymer-based light emitting diodes. Based on the one- dimensional tight-binding Su-Schrieffer-Heeger （SSH） model, we have investigated polaron dynamics in a one- dimensional polymer/polymer system by using a nonadiabatic evolution method. In particular, we focus on how a polaron migrates through the conjugated polymer/polymer interface in the presence of external electric field. The results show that the migration of polaron at the interface depends sensitively on the hopping integrals, the potential barrier induced by the energy mismatch, and the strength of applied electric field which increases the polaron kinetic energy.     

Polymer adsorption

We consider the adsorption of linear polymer and copolymer chains at surfaces and interfaces. We first remind de Gennes' theory for homopolymers, made of a single monomer species. Then we turn to multi block and random copolymers. In the latter case, we consider both cases when the A and B monomer species are distributed along the chain in a noncorrelated and correlated way, respectively. For each case, we discuss single chain adsorption and the saturation of the surface. Various measurable quantities are evaluated.     

Interpenetrating Polymer Networks

Interpenetrating polymer networks (IPNs) are a new class of polymer blends in network form in which at least one component is polymerized and/or cross-linked in the immediate presence of the other. IPNs possess several interesting characteristics in comparison to normal polyblends, because the varied synthetic techniques yield IPNs of such diverse properties that their engineering potential spans a broad gamut of modern technology. Interpenetrating polymer networks have shown excellent chemical resistance, hardness, elongation, tensile strength properties and higher compatibility. Hence, it can be concluded that using the IPN concept, it is possible to design the most desirable material for a specific end use requirement.     

液晶聚合物/柔性链聚合物共混体系相分离形态

利用元胞动力学方法在二维情况下对浓度、取向序参量的含时Ginzberg Landau方程进行数值求解 ,研究了液晶聚合物 /柔性链聚合物共混体系的相分离动力学 ,考察了浓度、取向有序过程的耦合对相分离形态的影响 .结果表明 ,此耦合作用对相分离的时间进程以及相分离图样的空间排布都有影响 .液晶聚合物的取向有序相当于增加了两组分间的不相容性而促进两相分离 ;两个序参量在热力学方面的耦合使液晶聚合物趋向于沿着界面方向取向 ,而动力学方面的耦合使液晶聚合物分子沿着其取向方向扩散 ,相分离图样的空间排布由这两种效应共同决定 .通过极化率张量的定义用数值方法模拟得到了相分离体系的小角光散射图样 ,结果表明 ,散射强度分布具有方位角依赖性 ,它是由浓度、取向序参量的空间变化共同决定的 .     

Ultraviolet-Cured Polymer Micro-Optical Elements

A new fabrication method for polymer micro-optical elements is described which uses the contracting effect of photopolymers during the process of polymerization. Convex and concave microlens arrays and phase gratings were formed by irradiating a ultraviolet (UV)-curable monomer with incoherent UV light through an appropriate metallic mask. The morphological and optical characterization of the fabricated elements reveals that the surface profile of the elements depends on the pattern and aperture size of the mask employed.     

高分子锚定的流体膜

将高分子自洽平均场理论和膜弹性理论结合起来研究高分子锚定流体膜体系，得到了高分子链热力学平衡浓度的分布和膜的形状.由于膜对高分子的不可穿透性，造成高分子可以实现的构象受到限制，导致高分子对膜施加不均匀的熵压，从而锚定点附近的膜弯离高分子，这些结果符合前人的理论分析和蒙特卡罗模拟的结果.此外，考察了膜和高分子链段之间的相互作用，高分子链长以及膜的弯曲刚性、张力对膜形变的影响. 关键词： 高分子 流体膜 自洽场理论 Helfrich膜弹性理论     

The Passive Polymer Problem

In this article, we introduce a generalization of the diffusive motion of point-particles in a turbulent convective flow with given correlations to a polymer or membrane. In analogy to the passive scalar problem we call this the passive polymer or membrane problem. We shall focus on the expansion about the marginal limit of velocity–velocity correlations which are uncorrelated in time and grow with the distance x as |x| , and small. This relation gets modified in the case of polymers and membranes (the marginal advecting flow has correlations which are shorter ringed.) The construction is done in three steps: First, we reconsider the treatment of the passive scalar problem using the most convenient treatment via field theory and renormalization group. We explicitly show why IR-divergences and thus the system-size appear in physical observables, which is rather unusual in the context of ordinary field-theories, like the ⁴-model. We also discuss, why the renormalization group can nevertheless be used to sum these divergences and leads to anomalous scaling of 2n-point correlation functions as e.g., S ²ⁿ (x)[(x, t)–(0, t)]²ⁿ . In a second step, we reformulate the problem in terms of a Langevin equation. This is interesting in its own, since it allows for a distinction between single-particle and multi-particle contributions, which is not obvious in the Focker–Planck treatment. It also gives an efficient algorithm to determine S ²ⁿ numerically, by measuring the diffusion of particles in a random velocity field. In a third and final step, we generalize the Langevin treatment of a particle to polymers and membranes, or more generally to an elastic object of inner dimension D with 0D2. These objects can intersect each other. We also analyze what happens when self-intersections are no longer allowed.     

多色高分子薄膜电致发光器件

采用多层高分子发光层和电极层结构实现了在同一ITO基片上产生红、绿、蓝三基色发光。得到电压阈值分别为：蓝色：2．5V,绿色：2．5V,红色：1．8V;发光量子效率：蓝色：2．5％,绿色：1．7％,红色：1．2％：色度坐标分别为：蓝色：(0．16,0．16),绿色：(0．34,0．58),红色：(0．60,0．39)。这种多层薄膜结构可能成为实现高分子彩色发光显示的新途径。     

Polymer stretching by turbulence

The stretching of a polymer chain by a large-scale chaotic flow is considered. The steady state which emerges as a balance of the turbulent stretching and anharmonic resistance of the chain is quantitatively described, i.e., the dependency on the flow parameters (Lyapunov exponent statistics) and the chain characteristics (the number of beads and the interbead elastic potential) is made explicit.     

Molecular structure of polystyrene at Air/Polymer and Solid/Polymer interfaces

IR-visible sum-frequency generation (SFG) spectroscopy has been used in a total internal reflection geometry to study the molecular structure of polystyrene (PS) at PS/sapphire and PS/air interfaces, simultaneously. The symmetric vibrational modes of the phenyl rings dominate the SFG spectra at the PS/air interface as compared to the antisymmetric vibrational modes at the PS/sapphire interface. This indicates approximately parallel orientation of the phenyl rings at the PS/air interface while nearly perpendicular orientation at the PS/sapphire interface, with respect to the surface normal.     

Crazes in Plasma-Modified Polymer Materials

Technical Physics - We report on the results of an analysis of the craze-formation center in plasma-modified polymers. It is shown that, as a result of plasma modification, oxidation, destruction,...     

Branching Features of a Polymer

Two parameters characterizing the branching features of polymers, branching density (BD), and branching completeness (BC), are proposed. Both have values of zero (0) for linear polymers. Branching density has the values of 1/2, 2/3, and (f – 2)/(f – 1) for the fully and densest branched polymers formed from tri-, tetra-, and f-functional monomers typed AB _{f –1}. Branching completeness will reach the value of one (1) for a completely branched polymer, where all possible branching monomeric units have reacted at least tri-functionally and all units are either terminal or dendritic. Branching density is close to the mole fraction of terminal units, and BC is close to the mole fraction of dendritic and terminal units in the branching polymers. The major advantage of these parameters is their independence of the degree of polymerization (dp). Branching density depends on the functionalities (f) of monomer units; BC does not. The higher the fraction of the dendritic unit monomerically bonded to a higher number of other units (the higher the terminal units fraction), the denser branched the polymer and the higher the BD. The BC and BD can be used in a simple way for describing multicharacter branching systems and for comparing the branching characters among them without any theoretical limitations. Physical quantities (namely, the number of dendritic and terminal units and the degree of polymerization) used for BD and BC evaluation can be determined directly from practical analyses, where NMR is most useful. The BC and BD, however, do not concisely describe branching characteristics for a polymer with cyclization or crosslinking in its structure.     

用于聚合物介电材料的双硅氧烷链接的环化聚合物

We studied the dielectric properties of organosilicon-containing helical cyclopolymer PbMA which consists of PMMA main chains and tetramethyldisiloxane side rings. PbMA formed films with excellent uniformity through spin-coating onto highly n-doped silicon (n-Si) wafers for constructing devices of dielectric measurements, on which the dielectric properties and I-V characteristics of PbMA were studied. PbMA has a much lower dielectric constant (lower than 2.6) in the frequency range of 10-10⁵ Hz, and better thermal stability than PMMA does. I-V data showed that the metal/PbMA/n-Si devices have different conducting directions, depending on whether Au or Al deposited over PbMA layers.     

Electron Microscopy in Polymer Science

In many fields of research in science, engineering, and medicine, electron microscopy as a method for directly imaging submicroscopic structures has become increasingly important in recent decades. Electron microscopy (EM) includes several different techniques: conventional transmission electron microscopy (TEM), high-resolution electron microscopy (HREM), highvoltage electron microscopy (HVEM), scanning electron microscopy (SEM), analytical electron microscopy (AEM), emission electron microscopy (EEM), and others. In the past the central aim of using electron microscopy was structure determination, but recently it has been of growing importance for also investigating different processes, i.e., changes in materials by interaction with several influential factors (e.g., heat, electric or mechanic fields, mechanical loading). Of particular interest is the study of the micromechanical processes of deformation and fracture. Therefore, electron microscopy is a very powerful tool for materials science. The present review reports on some capabilities and limitation of the application of electron microscopy to solid polymers. In Section II the techniques of electron microscopy are briefly reviewed, followed by a section that describes the main methods of specimen preparation of solid polymeric materials. In Section IV the results of several applications of electron microscopy are discussed to reveal the morphology as well as the micromechanical deformation processes of several polymeric materials.     

Polymer Transport in Random Flow

The dynamics of polymers in a random smooth flow is investigated in the framework of the Hookean dumbbell model. The analytical expression of the time-dependent probability density function of polymer elongation is derived explicitly for a Gaussian, rapidly changing flow. When polymers are in the coiled state the pdf reaches a stationary state characterized by power-law tails both for small and large arguments compared to the equilibrium length. The characteristic relaxation time is computed as a function of the Weissenberg number. In the stretched state the pdf is unstationary and exhibits multiscaling. umerical simulations for the two-dimensional Navier–Stokes flow confirm the relevance of theoretical results obtained for the -correlated model.     

Y分支有机聚合物热光开关的研制

利用有机聚合物材料热光效应进行Y分支结构光波导开关的研究和制作，实验结果显示光开关具有小于－20dB的串音，驱动功率为110mW-130mW。同时给出插入损耗的测试结果，并分析了其产生的各种原因。针对器件的开关速度问题，提出了解决方法。     

Delocalization in Random Polymer Models

 A random polymer model is a one-dimensional Jacobi matrix randomly composed of two finite building blocks. If the two associated transfer matrices commute, the corresponding energy is called critical. Such critical energies appear in physical models, an example being the widely studied random dimer model. It is proven that the Lyapunov exponent vanishes quadratically at a generic critical energy and that the density of states is positive there. Large deviation estimates around these asymptotics allow to prove optimal lower bounds on quantum transport, showing that it is almost surely overdiffusive even though the models are known to have pure-point spectrum with exponentially localized eigenstates for almost every configuration of the polymers. Furthermore, the level spacing is shown to be regular at the critical energy. Received: 2 January 2002 / Accepted: 10 September 2002 Published online: 19 December 2002