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Prediction of the glass transition temperature for compatible polymer blends of varying compositions
Compatible polymer blends have been found to have widespread commercial applications. The simplest criterion for judging polymer—polymer miscibility in the solid state is the glass transition temperature (Tg), which can vary widely according to blend composition for a compatible system.Recently, an equation which predicts the Tg of intimate mixtures of compatible polymers has been derived, based on classical thermodynamics. Only a knowledge of the Tg and heat capacity increment (ΔCp) of each pure component is required to predict the Tg at any composition.In this paper, the validity of this entropy-based relationship is investigated for a variety of commercial compatible polymer blends, including some based on poly(vinyl chloride), polystyrene, and poly(2,6-dimethyl-,4-phenylene oxide). The Tg and ΔCp of each pure component are measured with a Perkin-Elmer DSC-2 differential scanning calorimeter, are predicted glass transition temperatures are compared with those observed experimentally. 相似文献
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Helmut Bahrmann Klaus Bergrath Han -Jerg Kleiner Peter Lappe Christoph Naumann Dieter Peters Dieter Regnat 《Journal of organometallic chemistry》1996,520(1-2):97-100
BINAS is a new, very efficient ligand for propylene hydroformylation. BINAS is made by the sulfonation of NAPHOS. Different synthetic routes to NAPHOS are discussed. A new two step synthesis starting from 2,2′-bis(bromomethyl)-1,1′-binaphthyl is described. 相似文献
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On Heterocvclic Systems Containing Lead. II. Diphenyl Substituted Thiaplumbocanes, Examples for Expanding Coordination Tetrahedra around PbIV 5, 5-Diphenyl-1, 4, 6, 5-oxadithiaplumbocane (PbO8Ph2) and 2, 2-diphenyl-1, 3, 6, 2-trithiaplumbocane (PbS8Ph2) have been synthesized from diphenyl lead diacetate and the respective disodium dithiolates. The mass spectra point to rearrangements induced by reduction of PbIV to PbII in addition to fragments containing PbIV. 13C and 207Pb NMR spectra exhibit a weaker 1, 5-transannular interaction S …? Pb than O …? Pb. The crystal structures of two modifications of PbO8Ph2 (orthorhombic and triclinic) have been determined at ? 160°C and refined to R = 0.027 and 0.071. The two modifications contain four 8-membered rings crystallographical independent, three times chair-chair, once boat-chair conformation. Eight independent PbIV? S single bond distances range from 248.2(3) to 251.9(6) pm. The tetrahedral C2PbS2 configuration is expanded by one 1,5-transannular O …? Pb interaction (285,5(5) to 308(1) pm, monocapped) and further in the triclinic case by one intermolecular S …? Pb interaction (411(1) and 375(1) pm, bicapped). The crystal structure of the orthorhombic modification contains layers (8-membered ring) (phenyl)2 analogous to the structure of CdI2. In the triclinic case there are dimers arranged in analogy to the cubic closest packing. 相似文献
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Dr. Dorian Didier Dr. Pierre‐Olivier Delaye Marwan Simaan Biana Island Dr. Guillaume Eppe Dr. Hendrik Eijsberg Amir Kleiner Prof. Dr. Paul Knochel Prof. Dr. Ilan Marek 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(4):1038-1048
The copper‐catalyzed carbomagnesiation reaction of cyclopropenyl esters 1 leads to various substituted cyclopropanes species 3 in good yields with very high diastereoselectivities. The reaction proceeds through a syn‐chelated carbomagnesiation reaction and could be extended to various cyclopropenylmethyl ester derivatives 5 . The potential of this approach was illustrated by the preparation of two consecutive all‐carbon quaternary stereocenters. However, the carbometalation reaction needs to be performed at temperature ranging from ?35 to ?20 °C to avoid subsequent fragmentation reaction into stereodefined β,γ‐nonconjugated unsaturated esters 4 . Alternatively, the carbocupration reaction with organocopper species could also be performed to leads to configurationally stable cyclopropyl copper species 2[Cu] . Additionally, when the Lewis acid character of the copper center is decreased (i.e., RCuCNLi), the reaction proceed with an anti‐selectivity. The diastereodivergent behavior of these organometallic species is of synthetic interest, since both diastereomers syn‐ 3 and anti‐ 3 can be obtained, at will, from the same precursor cyclopropenyl esters 1 . 相似文献
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Probing the CH⋅⋅⋅π Weak Hydrogen Bond in Anesthetic Binding: The Sevoflurane–Benzene Cluster 下载免费PDF全文
Nathan A. Seifert Dr. Daniel P. Zaleski Dr. Cristóbal Pérez Dr. Justin L. Neill Prof. Brooks H. Pate Montserrat Vallejo‐López Prof. Alberto Lesarri Dr. Emilio J. Cocinero Prof. Fernando Castaño Prof. Isabelle Kleiner 《Angewandte Chemie (International ed. in English)》2014,53(12):3210-3213
Cooperativity between weak hydrogen bonds can be revealed in molecular clusters isolated in the gas phase. Here we examine the structure, internal dynamics, and origin of the weak intermolecular forces between sevoflurane and a benzene molecule, using multi‐isotopic broadband rotational spectra. This heterodimer is held together by a primary C? H???π hydrogen bond, assisted by multiple weak C? H???F interactions. The multiple nonbonding forces hinder the internal rotation of benzene around the isopropyl C? H bond in sevoflurane, producing detectable quantum tunneling effects in the rotational spectrum. 相似文献