Heat-set gel-like networks of lipophilic Co(II) triazole complexes in organic media and their thermochromic structural transitions

A novel class of thermally responsive supramolecular assemblies is formed from the lipophilic cobalt(II) complexes of 4-alkylated 1,2,4-triazoles. When an ether linkage is introduced in the alkylchain moiety, a blue gel-like phase is formed in chloroform, even at very low concentration (ca. 0.01 wt %, at room temperature). The blue color is accompanied by a structured absorption around 580-730 nm, which is characteristic of cobalt (II) in the tetrahedral (T(d)) coordination. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) of the gel-like phase confirms the formation of networks of fibrous nanoassemblies with widths of 5-30 nm. The observed widths are larger than a molecular length of the triazole ligand (ca. 2.2 nm) and they are consisted of aggregates of T(d) coordination polymers. Very interestingly, the blue gel-like phase turned into a solution by cooling below 25 degrees C. A pale pink solution is obtained at 0 degrees C, indicating the formation of octahedral (O(h)) complexes. The observed thermochromic transition is totally reversible. The formation of gel-like networks by heating is contrary to the conventional organogels, which dissolve upon heating. Temperature dependence of the storage and loss moduli (G' and G") shows minima around at 27 degrees C, at which temperature they gave comparable values. On the other hand, G' exceeds G" both in the gel-like phase (temperature above 27 degrees C) and in the solution phase (temperature below 25 degrees C). These observations indicate that T(d) complexes are present as low-molecular weight species around at 25-27 degrees C. They are self-assembled to polymeric T(d) complexes by heating and form gel-like networks. Upon cooling the solution below 25 degrees C, T(d) complexes are converted to O(h) complexes and they also self-assemble into oligomeric or polymeric species at lower temperatures. The observed unique thermochromic transition (pink solution --> blue gel-like phase) is accompanied by an exothermic peak in differential scanning calorimetry (DSC), and is shown to be an enthalpy-driven process. The lipophilic modification of one-dimensional coordination systems provides unique solution properties and it would be widely applicable to the design of thermoresponsive, self-assembling molecular wires.     

银纳米线表面等离激元波导的能量损耗

金属纳米结构的表面等离激元可以突破光学衍射极限,为光子器件的微型化和集成光学芯片的实现奠定基础.基于表面等离激元的各种基本光学元件已经研制出来.然而,由于金属结构的固有欧姆损耗以及向衬底的辐射损耗等,表面等离激元的传输能量损耗较大,极大地制约了其在纳米光子器件和回路中的应用.研究能量损耗的影响因素以及如何有效降低能量损耗对未来光子器件的实际应用具有重要意义.本文从纳米线表面等离激元的基本模式出发,介绍了它在不同条件下的场分布和传输特性,在此基础上着重讨论纳米线表面等离激元传输损耗的影响因素和测量方法以及目前常用的降低传输损耗的思路.最后给出总结以及如何进一步降低能量损耗方法的展望.表面等离激元能量损耗的相关研究对于纳米光子器件的设计和集成光子回路的构建有着重要作用.     

Adhesive effect of high density polyethylene gels on polyethylene moldings

Adhesive effect of polyethylene moldings by use of high density polyethylene gels in organic solvents such as decalin, tetralin, ando-dichlorobenzene was investigated by shearing tests, electron microscope, and DSC measurements. All of the gels showed such a strong adhesive strength over 36 kg/cm² that polyethylene plates of 3 mm in thickness gave rise to necking sufficient for practical use, when heated at 120 °C for 2 h. In particular, the gel in tetralin showed a strong adhesive strength when heated at 110 °C. It was found that adhesive strength increases with the heating temperature; the temperatures at which adhesive strength begins to increase differ depending on the type of polyethylene sample and solvent. It is apparent that polyethylene gels exhibit an adhesive effect when they are heated at higher temperatures than the gel melting temperatures, and that the closer the SP values of solvents used for the gelation are to the molded polyethylene, the stronger the adhesion of the polyethylene molding.     

Sandwich theorem for quasiconvex functions and its applications

In convex programming, sandwich theorem is very important because it is equivalent to Fenchel duality theorem. In this paper, we investigate a sandwich theorem for quasiconvex functions. Also, we consider some applications for quasiconvex programming.