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991.
Maurizio Galimberti Emilio Martini Fabrizio Piemontesi Franco Sartori Isabella Camurati Luigi Resconi Enrico Albizzati 《Macromolecular Symposia》1995,89(1):259-275
In this paper, new polyolefin elastomers, obtained from metallocene based catalytic systems, are presented. The potentialities of metallocenes for the preparation of polyolefin elastomers are discussed with reference to the traditional vanadium and titanium based catalysts. The role played by a Ziegler - Natta catalyst, either stereospecific or aspecific, is discussed. 相似文献
992.
We introduce FCclasses3, a code to carry out vibronic simulations of electronic spectra and nonradiative rates, based on the harmonic approximation. Key new features are: implementation of the full family of vertical and adiabatic harmonic models, vibrational analysis in curvilinear coordinates, extension to several electronic spectroscopies and implementation of time-dependent approaches. The use of curvilinear valence internal coordinates allows the adoption of quadratic model potential energy surfaces (PES) of the initial and final states expanded at arbitrary configurations. Moreover, the implementation of suitable projectors provides a robust framework for defining reduced-dimensionality models by sorting flexible coordinates out of the harmonic subset, so that they can then be treated at anharmonic level, or with mixed quantum classical approaches. A set of tools to facilitate input preparation and output analysis is also provided. We show the program at work in the simulation of different spectra (one and two-photon absorption, emission and resonance Raman) and internal conversion rate of a typical rigid molecule, anthracene. Then, we focus on absorption and emission spectra of a series of flexible polyphenyl molecules, highlighting the relevance of some of the newly implemented features. The code is freely available at http://www.iccom.cnr.it/en/fcclasses/ . 相似文献
993.
Maurizio Penco Luciana Sartore Fabio Bigotti Gloria Spagnoli Fabrizio Ferrari Salvatore D'Antone 《Macromolecular Symposia》2004,218(1):183-190
The compatibility of polystyrene (PS) with aromatic copolycarbonates containing bisphenol A (BPA) and tetramethyl bisphenol A (TMBPA) was investigated. The simple prevision scheme developed by Sonja Krause was employed to evaluate the effect of the copolymer molecular structure on the miscibility with polystyrene. These prevision data were used to select copolycarbonates of potential interest. Statistical copolycarbonates (CPC) containing different BPA/TMBPA molar ratios were synthesised by polycondensation reaction between a mixture of the two monomers and phosgene. PS/polycarbonates blends, prepared by casting from chloroform solution, were studied with differential scanning calorimetry and optical microscopy to evaluate the components compatibility, which increases with the TMBPA copolymer content. 相似文献
994.
Maria Carmela Sacchi Fabrizio Forlini Incoronata Tritto Paolo Locatelli 《Macromolecular Symposia》1995,89(1):91-100
The results of a study on a new generation of MgCl2 supported Ziegler-Natta catalysts that contain dialkyl propane diethers as internal donors and produce highly stereospecific polypropene even without any external donor are presented. The results concerning three different catalysts containing 2,2-diisobutyl-1,3-dimethoxy propane (DIBDMP), 2,2-dicyclopentyl-1,3-dimethoxy propane (DCPDMP) and 2-ethyl,2-butyl-1,3-dimethoxy propane (EBDMP) as internal donors are compared. The same donors have also been studied by using them as external donors with a catalyst contaning diisobutyl phthalate as internal donor. The present results, along with previously obtained findings on traditional supported Ziegler-Natta catalysts, permit a general comprehension of the role of internal and external donors. 相似文献