Rod syntheses

Fig. 10. A SEM micrograph of the cross-section of the deposited rod synthesized by the glow discharge shows an image of 1/4 of the cross-section of the deposited rod upper left corner of the image corresponds to the center of the end of the deposited rod.

Chang [99] produced polyimide (PI) fibers (obtained after thermal imidization of poly(amic acid) electrospun fibers) covered by rods of ZnO. First, the authors coated the PI nanofibers with ZnO NPs by immersion of the mat in an ethanol solution of zinc acetate and by performing a subsequent thermal treatment. These ZnO NPs acted as seeds for the growth of ZnO rods synthesized by hydrothermal synthesis, which occurred at 90°C in a mixture of zinc nitrate hexahydrate and hexamethylenetetramine. In order to improve the attachment of ZnO rods to the fiber surfaces, Kim et al. [100] incorporated the ZnO NPs seeds in the fiber by electrospinning a colloidal solution of polymer (nylon-6) and ZnO NPs. 

The wide variety of ketomethylene and amino ketone monomers that could be synthesized, and the abiUty of the quinoline-forming reaction to generate high molar mass polymers under relatively mild conditions, allow the synthesis of a series of polyquinolines with a wide stmctural variety. Thus polyquinolines with a range of chain stiffness from a semirigid chain to rod-like macromolecules have been synthesized. Polyquinolines are most often prepared by solution polymerization of bis(i9-amino aryl ketone) and bis (ketomethylene) monomers, where R = H or C H, in y -cresol with di-y -cresyl phosphate at 135—140°C for a period of 24—48 h (92). 

Metallomesogens. It is also possible to synthesize compounds based on metal atoms which possess Hquid crystal phases. The series based on dithiolene complexes (1), where M = Ni, Pd, or Pt, contains a number of compounds which show the Hquid crystal phases typical of rod-like molecules (13,14). 

Intractable, rigid, rod-like polyimides have been synthesized by way of polyisoimides (50). A large number of high molecular weight polyisoimides were also synthesized and characterized for the purpose of preparing semiinterpenetrating (SIPN) polyimide matrices and adhesives (51—53). 

Fig. 20.2 TEM images of NiS nanocrystals synthesized at 190°C for 1.5 h by a solventless method. The region (a) is enriched in prisms and (b) is enriched in rods [5],...

These rod-shaped ligands share a sterically efficient terminal N-donor and their divalent Co chemistry is well established. They will be discussed here only with selected examples. [Co (NCMe)6](TFPB)2 (TFPB- = tetrakis(3,5-bis(trifhioromethyl)phenyl)borate)) has been synthesized and characterized in the solid state along with a number of other divalent transition metal analogs.357 As a result of the extremely poor coordinating ability of the anion and facile loss of MeCN ligands from the cation, the salt is an excellent source of naked Co2+ ions. Thermolysis up to 100 °C leads to the loss of one MeCN and formation of a r -bound nitrile, whereas above 130 °C decomposition occurs with loss of MeCN and abstraction of fluoride from the anion to form CoF2. 

Even larger, conjugated systems were synthesized by employing both difunctional isocyanides and difunctional alkynes. In all the cases, the components have structural rigidity, which lends rigid-rod character to the complexes prepared from them. Many of the complexes are associated via intermolecular aurophilic contacts, which appear to have a distinct influence on the photophysical behavior, but are as yet not a necessary condition for luminescence (Scheme 51).196... 

Z. Gan and R. Roy, Transition metal-catalyzed syntheses of rod-like thioglycoside dimers, Tetrahedron Lett., 41 (2000) 1155-1158. 

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