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71.
Jeremy R. Lizotte Brian M. Erwin Ralph H. Colby Timothy E. Long 《Journal of polymer science. Part A, Polymer chemistry》2002,40(4):583-590
The feasibility of utilizing stable free‐radical polymerization (SFRP) in the synthesis of well‐defined poly(2‐vinylnaphthalene) homopolymers has been investigated. Efforts to control molecular weight by manipulating initiator concentration while maintaining a 2,2,6,6‐tetramethylpiperidinyl‐1‐oxy (TEMPO):benzoyl peroxide (BPO) molar ratio of 1.2:1 proved unsuccessful. In addition, systematic variations of the TEMPO: BPO molar ratio did not result in narrow molecular weight distributions. In situ Fourier transform infrared spectroscopy (FTIR) indicated that the rate of monomer disappearance under SFRP and thermal conditions were identical. This observation indicated a lack of control in the presence of the stable free radical, TEMPO. The similarities in chemical structure between styrene and 2‐vinylnaphthalene suggested thermally initiated polymerization occurred via the Mayo mechanism. A kinetic analysis of the thermal polymerization of styrene and 2‐vinylnaphthalene suggested that the additional fused ring in 2‐vinylnaphthalene increased the propensity for thermal polymerization. The observed rate constant for thermal polymerization of 2‐vinylnaphthalene was determined using in situ FTIR spectroscopy and was one order of magnitude greater than styrene, assuming pseudo‐first‐order kinetics. Also, an Arrhenius analysis indicated that the activation energy for the thermal polymerization of 2‐vinylnaphthalene was 30 kJ/mol less than styrene. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 583–590, 2002; DOI 10.1002/pola.10131 相似文献
72.
Olga Taussky Alfred P. Sloan 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1979,30(2):370-373
Matrices and operators of the formA
–1
A
* have received a certain amount of attention in recent years. Here some of the literature is surveyed and the caseA
–1
A is studied for complex matrices withA denoting the transpose ofA. A generalization ofA
–1
A is introduced.
Dedicated to Eduard Stiefel by a long time admirer 相似文献
Zusammenfassung Matrizen und Operatoren, die in der FormA –1 A * ausgedrückt werden können, sind in den letzten Jahren häufig studiert worden. Hier wird ein Ueberblick über Teil der relevanten Literatur gegeben und auch der FallA –1 A für komplexe Matrizen studiert, wobeiA die Transponierte vonA ist. Es wird auch eine Verallgemeinerung vonA –1 A eingeführt.
Dedicated to Eduard Stiefel by a long time admirer 相似文献
73.
Dispersion-corrected density functional theory method was performed to report on a high-performance adsorbent for removal of CO2 from the precombustion and natural gases. At first, the effect of Al atom impurity on the structural and electronic properties of B80 fullerene is studied. Then, the adsorption geometries and energies of gases (H2, CH4, or CO2) on the B80 and AlB79 (amphoteric adsorbents) are explored. The Al atom enhances reactivity of the cage toward the gases and the adsorption processes are more exothermic with low and high energy barriers for chemisorption of H2 and CO2, respectively. Stable chemisorption of CO2 on the AlB79 is validated by the high adsorption energy and large charge transfer, while the CH4 is just physically adsorbed on the AlB79. Further, the physisorbed gases can enhance field emission current of the AlB79 and in the continuous capturing of the gases, the magnetic moment of the cage is quenched. Furthermore, dependency of the electronic structure of the adsorbent on the gas adsorption is intensively studied. We suggest that the AlB79 could be a promising material for capture, storage, and separation of the gases and as a novel material for sustainable energy and sweetening process in the petroleum industry. 相似文献
74.
75.
Affine semigroups are convex sets on which there exists an associative binary operation which is affine separately in either variable. They were introduced by Cohen and Collins in 1959. We look at examples of affine semigroups which are of interest to matrix and operator theory and we prove some new results on the extreme points and the absorbing elements of certain types of affine semigroups. Most notably we improve a result of Wendel that every invertible element in a compact affine semigroup is extreme by extending this result to linearly bounded affine semigroups. 相似文献
76.
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78.
A convenient method has been developed for directly converting esters to amides using reagents derived from the reaction of trimethylaluminum with ammonium chloride, methylamine hydrochloride or dimethylamine hydrochloride. 相似文献
79.
80.