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Situ Preparation (situ + preparation)
Selected AbstractsIn situ Preparation of Polyimide Composites Based on Functionalized Carbon NanotubesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 2 2009Rohit Srivastava Abstract Three series of composite films based on polyimide and MWNTs were prepared by conversion of pyromellitic dianhydride and 4,4,-oxydianiline in the presence of the nanotubes, followed by thermal imidization. Carboxy- and amino-functionalized as well as unmodified nanotubes were used. It was demonstrated that just 0.5 wt.-% of nanotubes increased the tensile properties of the composite films distinctly. Surprisingly, a significant influence of the functional groups on the mechanical performance of the composite films could not be demonstrated. However, it was shown that functional groups may reduce the conductivity of the films. Furthermore, the influence of ultrasonication is discussed. [source] ChemInform Abstract: A Convenient in situ Preparation of Triphenylbismuthane (Tropon-2-yl)imide: Reaction with Heterocumulenes and Activated Alcohols.CHEMINFORM, Issue 30 2001Makoto Nitta Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Generation of Monodisperse Inorganic,Organic Janus Microspheres in a Microfluidic DeviceADVANCED FUNCTIONAL MATERIALS, Issue 10 2009Naveen Prasad Abstract This study presents a simple synthetic approach for the in situ preparation of monodisperse hybrid Janus microspheres (HJM) having organic and inorganic parts in a PDMS-based microfluidic device. Based on the mechanism of shear-force-driven break-off, merged droplets of two photocurable oligomer solutions having distinctive properties are generated into an immiscible continuous phase. Functionalized perfluoropolyether (PFPE) as the organic phase and hydrolytic allylhydridopolycarbosilane (AHPCS) as the inorganic phase are used for the generation in aqueous medium of HJM with well-defined morphology and high monodispersity (average diameter of 162,µm and a 3.5% coefficient of variation). The size and shape of the HJM is controlled by varying the flow rate of the disperse and continuous phases. The HJM have two distinctive regions: a hydrophobic hemisphere (PFPE) having a smooth surface and a relatively hydrophilic region (AHPCS) with a rough, porous surface. In addition, pyrolysis and subsequent oxidation of these HJM convert them into SiC-based ceramic hemispheres through the removal of the organic portion and etching off the silica shell. The selective incorporation of magnetic nanoparticles into the inorganic part shows the feasibility of the forced assembly of HJM in an applied magnetic field. [source] Selective Oxidative Ligand Coupling of Organoborates Bearing an Alkynyl GroupADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7-8 2009Toru Amaya Abstract Selective oxidative ligand coupling of alkynyl(triaryl)borates was achieved by treatment with ethoxyvanadyl dichloride [VO(OEt)Cl2] to form the spsp2 carbon-carbon bond. A one-pot procedure through the in situ preparation of the borate was demonstrated using triphenylborane and 1-ethynyl-4-methoxybenzene. [source] Monitoring ultrathin film photopolymerization of tetra-alkylepoxyporphyrin by UV-Vis spectroscopyJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2009Kalle Lintinen Abstract Cationic photopolymerization is a convenient in situ polymerization method for organic thin film preparation. In this work, the polymerization mechanisms is applied for highly viscous cross-linking monomers, using tetra-alkylepoxyporphyrin (TAEP) as a case study. By comparing the UV-Vis spectra of the polymerized sample before and after the unreacted monomers have been dissolved, it is possible to estimate the polymerization yield. An IR spectrum of a reference thick film confirms full polymerization. Scanning fluorescence lifetime microscopy and AFM show the uniformity of the polymer. It was shown that photopolymerization is highly dependent on the substrate nature and requires at best case a 10 min illumination at 90 °C. Thermal polymerization of the same sample requires 10 min heating at 150 °C in dark. It was also shown that TAEP works as a self-sensitizer for cationic photopolymerization. The proposed method is a mild and versatile technique for in situ preparation of thin polymeric films directly from chromophore monomers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6095,6103, 2009 [source] Formation of Fibril Structures in Polymerizable, Rod,Coil-Oligomer-Modified Epoxy NetworksCHEMISTRY - A EUROPEAN JOURNAL, Issue 10 2007Yingfeng Yu Dr. Abstract This paper describes the in situ preparation of fibrils in epoxy networks in which the fibril-like structures are cured polymerizable rod,coil oligomers. The epoxy-terminated ,,,-modified PEO oligomers, which are ABA rod,coil,rod oligomers with a poly(ethylene oxide) coil unit and two aromatic azomethine liquid-crystalline rod units, were synthesized and then further blended with an epoxy precursor. Uniform nanoscale columnar structures were observed in the neat rod,coil oligomers as well as in the crosslinked liquid-crystalline state. During the curing of the blends, the supramolecular nanoscale columnar structures of the rod,coil oligomers are transformed into polymeric fibrils where the epoxy functional end groups have co-reacted with epoxy precursors to form a crosslinked network. [source] Direct loading of Nobel Direct® and Nobel Perfect® one-piece implants: a 1-year prospective clinical and radiographic studyCLINICAL ORAL IMPLANTS RESEARCH, Issue 4 2007Per-Olov Östman Abstract Objectives: The aim of this prospective study was to evaluate the Nobel Direct® and Nobel Perfect® one-piece implants (OPIs) when used for immediate function. Material and methods: Forty-eight patients were provided with 115 OPIs for loading with a provisional crown or a bridge within 24 h and followed for at least 12 months with clinical and radiographic examinations. A group of 97 patients previously treated under identical conditions by the same team with 380 two-piece implants (TPIs) for immediate loading in the mandible and maxilla served as the reference group. Results: Six (5.2%) OPIs failed during the follow-up due to extensive bone loss. Five (1.3%) implants failed in the reference group. After 1 year, the mean marginal bone loss was 2.1 mm (SD 1.3) for OPIs and 0.8 mm (SD 1) for TPIs. 20% of OPIs showed more than 3 mm of bone loss compared with 0.6% for TPIs. When compensating for vertical placement depth, OPIs still showed a lower marginal bone level and thus more exposed threads than TPIs. Depending on the criteria used, the success rate for OPIs was 46.1% or 72.2% compared with 85% or 91.6% for TPIs. Conclusions: The Nobel Direct® and Nobel Perfect® OPIs show lower success rates and more bone resorption than TPIs after 1 year in function. Factors such as implant design, insertion depth, rough surface towards the mucosa, in situ preparation and immediate loading may have an influence on the clinical outcome. [source] Nanostructure and micromechanical properties of reversibly crosslinked isotactic polypropylene/clay compositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010S. Bouhelal Abstract Recent developments concerning the methodology used to prepare composites of iPP and nanoclays are reported. Conventional (reactive melt mixing) and in situ preparations were performed, and the structural properties exhibited by the composites are discussed. Results suggest that the nanoclay could exhibit partial and, maybe, total exfoliation within the composites. Adhesion between the polymeric matrix and the nanoclay layers is similar to that obtained after grafting. The experimental procedure used and the analysis performed by means of the wide-angle X-ray scattering and differential scanning calorimetry techniques permit to describe, at nanoscale level, the contribution of the nanoclay to the polymer composite system. The microhardness values of the iPP,clay composites depend on the clay content and on the preparation method, and linearly correlate, according to the additivity law, with the degree of crystallinity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] | |||||||||||||