912 resultados para POLYMERIZATION KINETICS


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The present communication studies the adsorption of aniline on platinum single crystal electrodes and the electrochemical properties of the first layers of polyaniline(PANI) grown on those platinum surfaces. The adsorption process was studied in aqueous acidic solution (0.1 M HClO4) and the electrochemical properties of thin films of PANI in both aqueous (1 M HClO4) and non-aqueous media (tetrabutyl ammonium hexafluorophosphate (TBAPF6) with additions of methanesulphonic acid in acetonitrile). First of all, it was found that the adsorption of aniline on platinum single crystal surfaces is a surface sensitive process, and even more important that the adsorption features found at low concentrations (5 × 10−5 M) can be directly correlated to the electrochemical properties of thin films of PANI in the very early stages of polymerization. The Pt(1 1 0) surface was found to be more suitable to obtain polymers with more reversible redox transitions when studied in aqueous media (1 M HClO4). This is in good agreement with the higher polymerization rates found on this surface compared to Pt(1 0 0) and Pt(1 1 1). Finally the differences in ionic exchange rate were greatly enhanced when they were studied in organic media. The AC 250 Hz response in the case of the thin films synthesized on Pt(1 1 0) is about twice greater than that obtained in the other basal planes using polymer layers with the same thickness.

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This paper addresses the problem of predicting the critical parameters that characterize thermal runaway in a tubular reactor with wall cooling, introducing a new view of the n-th order kinetics reactions. The paper describes the trajectories of the system in the temperature-(concentration)n plane, and deduces the conditions for the thermal risk.

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The grafting of functional brushes on the surface of molecularly imprinted polymer (MIP). particles hás been explored in the last few years to synthesize materiais combining high molecular recognition capabilities and stimulation triggered by changes in the surrounding environment [1, 2]. In the present work, MIP particles for 5-fluorouracil (a drug used in câncer treatment) were produced by precipitation polymerization in acetonitrile, using either MAA or HEMA as imprinting fünctional monomers, and m the presence of different kinds of RAFT agents. In a second step, taking advantage of the RAFT groups present in the surface of the particles, different kinds of fiinctional polymer brushes were grafted on the MIPs considering a "grafting from" process in the presence of a RAFT agent.

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Mode of access: Internet.

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"July 18, 1958."

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"September 23, 1955."

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This bibliography contains 417 annotated references on uses of isotopes in industry and in chemical reaction mechanisms and kinetics. The references were taken from the 1957-1958 open literature. Also included are a list of journals from which the references were selected, an author index, an isotope index, and a graphical depiction of typical applications.

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At head of title: Combustion Dynamics Division, Air Force Office of Scientific Research, ARDC, Washington, D. C., File no. AF 18(600)-1332.

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"Prepared for U.S. Atomic Energy Commission under contract W-7405-eng-92."

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"Category No. UC-4 ; Chemistry ; TID-4500."

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"Unclassified."