POSS‐nylon 6 nanocomposites: Influence of POSS structure on surface and bulk properties

Hybrid organic/inorganic nanocomposites based on polyhedral oligomeric silsesquioxane (POSS) nanostructured chemicals and nylon 6 were prepared via melt mixing. Two structurally and chemically different POSS molecules, a closed cage, nonpolar octaisobutyl POSS (Oib‐POSS) and an open cage, polar trisilanolphenyl POSS (Tsp‐POSS) with differing predicted solubility parameters were evaluated in the nylon matrix. Surface analysis, including quasi‐static and dynamic nanoindentation and nanotribological techniques, revealed exceptional improvements in modulus and hardness along with significant reductions in friction. Additionally, surface wetting characteristics of the nylon were reversed, with POSS incorporation yielding low surface energy, highly hydrophobic surfaces. AFM, TEM/EDAX, spectroscopic techniques and thermomechanical analysis were used to evaluate nanoscale dispersion and bulk properties of the composites. Both POSS molecules exhibit preferential surface segregation behavior in the nylon matrix. Tsp‐POSS, with its higher predicted solubility in nylon, exhibited enhanced dispersion and tribomechanical properties at both nano and bulk scale. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1088–1102, 2009     

A “plug and play” polymer through biocomplementary hydrogen bonding

This article describes a DNA‐like polymer that exhibits the ability to self‐assemble through hydrogen bonding. We synthesized poly[1‐(4‐vinylbenzyl)thymine] (PVBT) and 9‐hexadecyladenine (A‐C16) through an atom transfer radical polymerization (ATRP) and alkylation, respectively. Biocomplementary PVBT/A‐C16 hierarchical supramolecular complexes formed in dilute DMSO solution through nucleobase recognition, that is, hydrogen bonding interactions between the thymine (T) groups of PVBT and the adenine (A) group of A‐C16; evidence for this molecular recognition was also gained from dynamic light scattering studies. ¹H NMR titration studies in CDCl₃ showed that T–A complexes formed rapidly on the NMR time scale with high association constants (up to 534 M^?1). Moreover, FTIR spectroscopic, differential scanning calorimetry, wide‐angle X‐ray diffraction, and small‐angle X‐ray scattering analyses provided further details into the nature of the self‐assembly of these systems. In the bulk state, these complexes self‐assemble into well‐ordered lamellar structures; the changing d‐spacing distance (ranging from 4.98 to 2.32 nm) at different A‐C16 loadings reveals that the molecular structures of the PVBT/A‐C16 complexes are readily tailored. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6416–6424, 2008     

A Simple Criterion for the Existence of Rank-One Connections between Martensitic Wells

We show that for the two wells SO(3) U and SO(3) V to be rank-one connected, where the 3 × 3 symmetric positive definite U and V have the same eigenvalues, it is necessary and sufficient that det(U − V) = 0, a result that does not hold in higher dimensions. Using this criterion and a result of Gurtin, formulae for the twinning plane and the shearing vector are obtained, which yield an extremely simple condition for the occurrence of so-called compound twins. As an illustration, we apply our results to the cubic-to-monoclinic transition. This revised version was published online in August 2006 with corrections to the Cover Date.     

On some three-field mixed systems

In this work we present a modified mixed formulation for some three-field problems. Under a special hypothesis the modified formulation is such that: the verification of two (BB) conditions is avoided and one has to deal only with one, and the new problem has exactly the same solution as the old one. This revised version was published online in June 2006 with corrections to the Cover Date.     

A Note on Nonclassical Symmetries of a Class of Nonlinear Partial Differential Equations and Compatibility

The nonclassical symmetries of a class of nonlinear partial differential equations obtained by the compatibility method is investigated. We show the nonclassicaJ symmetries obtained in [J. Math. Anal. Appl. 289 （2004） 55, J. Math. Anal. Appl. 311 （2005） 479] are not all the nonclassical symmetries. Based on a new assume on the form of invariant surface condition, all the nonclassical symmetries for a class of nonlinear partial differential equations can be obtained through the compatibility method. The nonlinear Klein-Gordon equation and the Cahn-Hilliard equations all serve as examples showing the compatibility method leads quickly and easily to the determining equations for their all nonclassical symmetries for two equations.     

一个解决声纳系统同频干扰的新思路

多平台联合作战将是未来海上作战的重要形式之一,多部主动声纳的同时存在使声兼容问题十分突出。由于友舰直达波经历的是单程传播,其强度往往比经历了双程传播的目标回波大的多。通过波形设计可以获得相关系数小的声纳波形,虽然可以从一定程度上缓解声兼容问题,但由于获得的增益有限,并不能从根本上解决这一问题。本文通过对常规检测器的修正,引入能量归一化的概念,有效地消除了能量对检测器的影响,从而解决了这一问题。同时本文还提出了与现有声纳信号处理体系相兼容的频域实现方法,使该算法在工程上的实现成为可能。计算机仿真证明,这一方法是正确有效的。     

锂离子电池液体电解质与电极相容性的研究进展

随着锂离子电池商业化的不断发展,提高电池在室温及高温下的循环性和安全性已经引起了人们的高度重视.改善电解质与电极的相容性,提高电极表面钝化膜的稳定性是提高电池综合性能的有效途径.本文介绍了在优化电解质组成以及改善电解质与电极的相容性方面的研究进展,讨论了电解质各组分在电极上的作用机理.     

交换环的实V-赋值与亚序

在带有单位元的交换环上,引入了V-赋值与亚序间的相容性,并得出了一些性质。在此基础上,对环的实V-赋值进行了讨论,从而推广了实Manis赋值理论中许多的结论。     

聚己内酯分子量对乙基纤维素/聚己内酯共混体系的溶致性液晶织构的影响

利用偏光显微镜研究了乙基纤维素与聚己内酯共混物在二氯乙酸中的溶致性液晶形态。结果表明聚己内酯的分子量对共混体系的溶致性液晶结构有明显的影响。差示扫描量法测试显示含不同分子量聚己内酯的共混物,其混溶性及两组分间的相互作用无十分明显的差异。聚内酯分子量对共混体系溶致性液晶的形态和热稳定性的影响,可认为是由于分子量对体系的粘度贡献引起的。     

Engineering of the Filler/Polymer Interface in Metal–Organic Framework‐Based Mixed‐Matrix Membranes to Enhance Gas Separation

Traditional films cannot fully adapt to industrial applications and to intensified processes. Advanced mixed‐matrix membranes comprising metal–organic frameworks (MOF) embedded in a polymer matrix have been developed with the goal of breaking the trade‐off effect of traditional polymer membranes and achieving separation performance beyond Robeson's upper limit. The key challenges in the fabrication of MOF‐based mixed‐matrix membranes are an enhancement in compatibility between the inorganic filler and the polymer matrix, elimination of the irregular morphology and non‐selective interfacial defects, and further improvement in the gas‐separation performance. This review summarizes the recent advances in protocols and strategies in terms of designing interfacial interactions to enhance the MOF/polymer interface compatibility. This review aims at providing some meaningful insights into preparing MOF‐based mixed‐matrix membranes targeting ideal interfacial morphology and leading to excellent gas‐separation performance.