Geometrical Molecular Structure Design Concept in Approach to Homo- and Heterometallic Precursors of Advanced Materials in Sol–Gel Technology

The article describes the principles of the Single Source Precursor approach to inorganic materials and introduces the Geometrical Molecular Structure Design Concept (MSDC) based on the choice of a proper molecular structure type for the desired precursor and completing it with ligands providing both the necessary number of donor atoms and the sterical protection of the chosen core. Application of MSDC is illustrated with examples taken from development of new approaches in the synthesis of oxide and sulfide catalysts and ferroelectric oxide materials.     

Thermal decomposition of a generation 4.5 PAMAM dendrimer platinum drug conjugate

A nanoscale multivalent platinum drug based on a poly(amidoamine) [PAMAM] dendrimer (generation 4.5, carboxylate surface) has been synthesized and fully characterized using a variety of spectroscopic, chromatographic and thermal methods. Treatment of the dendrimer with an aqueous solution containing an excess diaquo(cis-1,2-diaminocyclohexane)platinum(II) produces a conjugate containing approximately forty (diaminocyclohexane)platinum(II) moieties at the surface of the dendrimer. This material undergoes smooth two-stage thermal decomposition to provide residual platinum oxide reflecting the platinum loading in the drug.     

Production of superfine fibers by the electrospinning method

Weakly conducting fluid flows in an electric field in the presence of phase interfaces are investigated theoretically and experimentally. The object of the investigation is an axisymmetric jet. The analysis is carried out within the framework of electrohydrodynamics (EHD) with allowance for surface charge transfer on mobile interfaces. The jet shape is calculated at large distances from the outflow point. The theoretical and experimental data are compared for Newtonian and polymeric fluids.     

Behaviors of the positive temperature coefficient of resistance of poly(styrene‐co‐n‐butylacrylate) filled with Ni‐plated core‐shell polymeric particles

Conductive composite films of poly(styrene‐co‐n‐butylacrylate) copolymers filled with low‐density, Ni‐plated core‐shell polymeric particles were prepared and their behaviors of positive temperature coefficient of resistance (PTCR) were investigated. When the conductive fillers in the composite film were loaded beyond the critical volume, 10 up to 25 vol %, composite films exhibited a unique electrical resistant transition behavior, which the electrical resistance rapidly increased by several orders of magnitude at the critical temperature. The PTCR transition temperature, in general, occurred before the glass transition temperature of polymer matrix. Further increased the conductive filler loading to 30 vol %, the overpacked conduction paths were formed in the entire composite and the PTCR effects became blurred. While the composite film treated with thermal cycle several times from room temperature up to 120 °C, the electrical resistivity increased accompanied with the shift of the PTCR transition to lower temperature. The reason might have been caused by the formed interfacial cracks within the composite film. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 322–329, 2007     

Rotational Motion of a Solute Molecule in a Highly Viscous Liquid Studied byC NMR: 1,3-Dibromoadamantane in Polymeric Chlorotrifluoroethene

The viscosity-dependent retarding effect of a polymeric solvent on the rotation of small solute molecules is investigated by¹³C NMR relaxation measurements. It is found that the relaxation data of 1,3-dibromoadamantane in highly viscous polymeric chlorotrifluoroethene can be explained neither by isotropic nor by realistic anisotropic tumbling in a single environment. The experimental data are rationalized in terms of fast exchange between at least two environments with correlation times differing by up to two orders of magnitude. The study shows that a uniform retardation of molecular tumbling by a polymeric solvent, desirable for shifting the NMR observation window in studies of intramolecular mobility, is not always feasible.     

Synthesis and characterization of novel perfluorinated polyimides with 3D‐controlled structures for photonic applications

We have designed and synthesized novel perfluorinated polyimides with 3D controlled structure. At first, we successfully developed the new synthetic routes to diamines with pendant bulky perfluorinated aromatic units in a multi‐step synthetic procedure. Novel perfluorinated polyimides were prepared in a two‐step reaction in N‐methyl‐2‐pyrrolidinone (NMP) solution: The first step was for the synthesis of polyamic acids (PAAs) and the second reaction was for the imidization of PAA. The polymer yield was over 89% and the inherent viscosity of PAAs was in the range of 0.24–0.36 dL/g. The thin films were prepared by spin‐coating the PAA solution in NMP onto various substrates such as a Si wafer or a KBr pellet, dried at 80 °C and further cured at 230 °C. The resultant polyimides are thermally stable over 400 °C. The refractive index and birefringence of the resultant polyimides are 1.5858–1.6452 and 0.01–0.005, respectively. The refractive index of polyimide decreases with increasing the fluorine content. The copolymerization and the ether linkages into the backbone reduce the birefringence of polyimides. Surprisingly, the pendant ether linkage is not a crucial factor in reducing the polyimide birefringence. Their birefringence is comparatively very low, compared with that of previous polyimides. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1326–1342, 2006     

A Novel Method to Synthesize Polyorganozircosilazane

A new kind of polyorganozircosilazane as Si/Zr/C/N-based ceramic precursor was synthesized from the condensation reaction of hexamethyleyclotrisilazane lithium salts(D3^NLi）and zirconium tetrachloride(ZrCl4).In the presence of N,N,N’,N’-tetramethyl ethylene diamine(TMEDA),polyorganozircosilazane was obtained in high yield.     

聚（2,5—二甲氧基对苯乙炔）的可溶性前聚物合成及表征

研究了合成聚（２，４－二甲氧基对苯乙炔）的有机可溶性前聚物的反应条件与单体转化率和前聚物产率的关系。实验结果表明：ＮａＯＨ是聚合反应的有效引发剂，适宜的反应条件为：单体与ＮａＯＨ摩尔比为１：１，单体浓度０．０５－０．２ｍｏｌ／Ｌ，聚合时间２ｈ，温度低５℃，正己烷、石油醚作为有机提取剂可有效提高前聚物产率。用ＩＲ、ＵＶ－Ｖｉｓ＇＾ＨＮＭＲ，ＴＧＡ和 ＤＳＣ对前聚物进行了表征。     

棒状钡铁氧体的反相微乳法制备

A rodlike barium ferrite precursor with an average size of 0.72～19.6 μm and aspect ratio of 2.6～8.3 has been successfully prepared in an inverse microemulsion consisting of isooctane, cetanyl trimethyl ammonium bromide (CTAB), n-C₄H₉OH and water with ammonia and ammonium oxalate as precipitants. On sintering at 780(C, the rodlike precursor particles could be transformed into rodlike particles of barium ferrite(BaFe₁₂O₁₉) with the average size and aspect ratio of 0.69～18.2 μm and 2.3～5.8, respectively. The effect of volume ratio of aqueous phase to oleic phase, the starting concentrations of metal ions and the starting concentration ratios of metal ions to precipitants were investigated.