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Study of Atrp Process for the Grafting of Vinyl Monomers on PVC and PVDF
No full textSTUDY OF ATRP PROCESS FOR THE GRAFTING OF VINYL MONOMERS ON PVC AND PVDF
Sonia Lanzalaco, Onofrio Scialdone, Alessandro Galia, Rosalia Mauro, Flavia Lazzano Dipartimento di Ingegneria Chimica, Gestionale, Informatica, Meccanica,
Viale delle Scienze, Palermo
e-mail: [email protected]
ATRP (atom transfer radical polymerization) has been recently used to prepare graft copolymers with regularly-spaced polymer chains from polymeric macroinitiators that have pendant chemical groups containing radically transferable halogen atoms [1]. The halogen atom serves as initiation site for the polymerization of side chains. Furthermore, Matyjaszewsky and Gennaro showed that an externally applied electrochemical potential can reversibly activate the copper catalyst for this process and demonstrated the dynamic modulation of polymerization rates through electrochemical means, fostering precise temporal control over initiation, cessation, and rejuvenation of the living process [2].
Our group has recently studied the atom transfer radical graft copolymerization by using halogen macroinitiators (polyvinylidenefluoride (PVDF) and polyvinylchloride (PVC) ) in organic media and used electrochemical approach to investigate the polymer effectiveness as ATRP macroinitiator and to detect the relative population of the redox couple Cu(I)/Cu(II) during the copolymerization . In particular in order to achieve preliminary information on the grafting of polyhydroxyethylmethacrylate on PVC and PVDF catalyzed by copper complexes, a study on the behavior of the various components of the system, such as halogenated polymer (PVC or PVDF), copper catalyst (CuCl or CuBr), ligand (TPMA or Me6TREN) , was carried out by cyclic voltammetric, chronoamperometric and spectrophotometric experiments. Some grafting experiments were also carried out in the more promising operative conditions.
[1] J. F. Hester, P. Banerjee, Y. Y. Won, A. Aktakul, M. H. Acar, A. M. Mayes, Macromolecules, 2002, 35, 7652.
[2] A. J. D. Magenau, N. Strandwitz, A. Gennaro, K. Matyjaszewski, Science, 332 (2011) 81-84
Utilization of Poly(vinylchloride) and Poly(vinylidenefluoride) as Macroinitiators for ATRP Polymerization of Hydroxyethylmethacrylate. Electroanalytical and Graft-Copolymerization Studies
No full textThe utilization of poly(vinylchloride) (PVC) and poly(vinylidenefluoride) (PVDF) as macroinitiators for
atom transfer radical polymerization (ATRP) of hydroxyethylmethacrylate (HEMA) was studied
performing electroanalytical investigations and “grafting from” experiments in order to achieve
information on the possibility of modifying such commercial polymers by this controlled free radical
polymerization technique.
This study was performed changing various operating parameters such as the nature of the copper
salt, the ligand, the solvent, the temperature and the reaction time. Electroanalytical data suggest
that PVC can be easily activated by both CuCl/ Tris(2-pyridylmethyl)amine (TPMA) and CuCl/ Tris[2-
(dimethylamino)ethyl]amine (Me6TREN), two catalytic systems widely adopted for ATRP reactions, in
a wide range of operating conditions. PVDF is more difficult to be activated, due to the higher
strength of the C-F bond. In particular, the utilization of high temperature and of a more reductant
redox couple such as Cu(I)Me6TREN/Cu(II)Me6TREN was needed to achieve a significant degree of
graftin
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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