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Elastomeric nanofibers composed of cross-linked poly(2-hydroxyethyl methacrylate) are synthesized via a reactive electrospinning process. In this process, the photoinduced polymerization and cross-linking of polymers take place simultaneously during the electrospinning process. The produced nanofibers are mostly within the diameter range of 100-500 nm in the dry state. When they are immersed in aqueous solution, the nanofibers exhibit remarkably large elastic properties characteristic of bulk hydrogel materials.

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Articles you may be interested inDissociation mechanisms of excited CH3X (X = Cl, Br, and I) formed via high-energy electron transfer using alkali metal targets

The film structure, composition, and deposition kinetics of model Ziegler-Natta polymerization catalysts produced by chemical vapor deposition have been studied using temperature-programmed desorption (TPD), Auger electron spectroscopy (AES), and X-ray photoelectron spectroscopy (XPS). Redox reactions of metallic Mg and TiCl 4 deposited from the vapor phase on a Au substrate produce the model catalysts composed of titanium chloride and magnesium chloride (TiCl x /MgCl 2 ). The low solubility of TiCl x in MgCl 2 leads to the formation of a TiCl x monolayer on top of MgCl 2 multilayers characteristic of the supported catalysts. The TiCl 4 /Mg flux ratio during the deposition controls the oxidation state distribution and surface coverage of TiCl x species of the deposited film. The conversion of Mg to MgCl 2 is completed in the codeposition process while it is incomplete in the sequential deposition process due to a kinetic barrier for chlorine diffusion. Upon heating the sequentially deposited film, the surface TiCl x (Ti 4+ ) species react with metallic Mg atoms in underlayers to complete the redox reaction. In the case of the codeposited film, the surface TiCl x species desorb as TiCl 4 at temperatures higher than 430 K. After exposure to triethylaluminum (AlEt 3 ) cocatalyst, the model catalyst films are active for propylene polymerization.

Temperature-programmed desorption (TPD) of physisorbed mesitylene molecules has been used as a nondestructive surface probe to distinguish the surface adsorption sites of model Ziegler-Natta polymerization catalysts. A MgCl2-supported titanium chloride film (TiClx/MgCl2) was fabricated on an inert gold substrate by codeposition of Mg metal and TiCl4 from the gas phase. The mesitylene TPD probe revealed two types of surface adsorption sites. The dominant site was attributed to the basal plane of these halide crystallites. The minor site could be tentatively attributed to a defective structure at the basal plane boundaries or other crystal planes. Due to the chlorine termination nature of the catalyst surface, the metal ions under the chlorine layer could not be differentiated directly with the physisorbed mesitylene molecules. However, the mesitylene TPD profile was able to monitor compositional changes in the outermost chlorine layer accompanying the reaction of the catalyst film with the triethylaluminum cocatalyst, electron beam irradiation of the film surface, and diffusion of bulk chlorine to minimize the number of defect sites.