1,721,249 research outputs found
Solvent and temperature effects on the chromic behaviour of poly[3-(10-hydroxydecyl)-2,5-thienylene]
No full textThe chromic behaviour of a soluble ω-hydroxydecyl 3-substituted polythiophene has been investigated by UV-VIS spectroscopy in different solvent/non-solvent mixtures over a wide range of low temperatures. Some interesting new effects have been observed that is the first case of a reversal of the solvatochromic transformation in substituted polythiopenes and a concentration effect in dilute pure solvent solutions. A molecular approach based on solvent-polymer interactions has been adopted to study the conformational chromic transformation of the polymer. © 2001 Elsevier Science B.V
Analysis of UV - Vis spectral profiles of solvatochromic poly[3-(10-hydroxydecyl)-2,5-thienylene]
No full textThe paper discusses a systematic study of the UV - Vis spectral profiles of poly[3-(10-hydroxydecyl)-2,5-thienylene] during its solvatochromic transformation in different solvent/non-solvent mixtures. A simulation of the overlapped spectra of the two chromophores (A less and B more conjugated) of the polymer is made through the resolution of their pure forms by means of vibronic progressions of log_normal curves. The increment of the absolute intensity observed in the transformation has been determined and related to the increment of the transition moment; its value strongly supports the hypothesis that the solvatochromic transition consists in a doubling of A chromophores. Estimation of the average length of B chromophores has made it possible to evaluate the oscillator strength in the different solvent mixtures, the Franck-Condon factor and the Huang-Rhys parameter in relation to the intensity distribution of the vibronic structure. © 2002 Elsevier Science B.V. All rights reserved
Chromic Effects in Poly (3-(10-hexanoyloxydecyl)-2,5-thienylene) as Precursor of ω-Hydroxydecyl-functionalized Polythiophene
No full textThe preparation of a hexanoyloxydecyl 3-substituted polythiophene and its conversion to the corresponding hydroxydecyl polymer, soluble in common organic solvents, is described. Solvatochromic and thermochromic effects of the two polymers were investigated by UV-vis spectroscopy in pure solvent and in solvent/nonsolvent solutions. A very different response was found depending on the type of functional group. The carboxylate polymer requires the synergy of both nonsolvent and low temperature for a strong chromic effect comparable to that of the hydroxy polymer to be observed. A possible explanation of this behavior is discussed. © 1998 John Wiley & Sons, Ltd
Anomalous solvatochromic effect. Comparison between decyl and ω-hydroxydecyl 3-substituted polythiophenes
No full textThe solvatochromic behavior of chloroform solutions of poly(3-decyl-2,5-thienylene), poly[3-(10-hydroxydecyl)-2,5-thienylene] and their copolymers was studied by the addition of the non-solvent methanol. A reversed chromic transformation was found associated with the content of the hydroxyalkyl substituent. This anomalous effect was investigated using a number of non-solvents, in particular aliphatic alcohols from methanol up to decanol. In the case of a chloroform/methanol mixture, which gives the maximum anomalous effect, the effect produced by temperature variation was also examined. An explanation based on a molecular approach was attempted
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
NOTA BENE: a metà 2003 ho cambiato cognome, aggiungendo il cognome "Morgera" a quello "Fraleoni". Il mio attuale e corretto cognome è quindi Fraleoni Morgera, ma fino a metà 2003 i miei articoli e contributi a congressi sono pubblicati con il solo cognome "Fraleoni". Ho inserito il mio attuale cognome "Fraleoni Morgera" in questo articolo poiché altrimenti il sistema non mi lascia inserire la pubblicazione. Per cortesia leggete il mio nome in questo articolo come “Fraleoni A”, e considerate che in caso di controlli sui motori di ricerca per trovare tutti i miei lavori indicizzati dovete ricercare il cognome "Fraleoni" come autore, e non "Fraleoni Morgera". Quest’ultima ricerca riporterebbe solo 24 delle mie 31 effettive pubblicazioni. PLEASE NOTE: around the middle of 2003 I changed my family name, adding the surname “Morgera” to “Fraleoni”. My current and correct family name is the “Fraleoni Morgera”, but until half of 2003 my scientific production was signed only as “Fraleoni”. I inserted my current family name “Fraleoni Morgera” in this contribution because otherwise the system does not allow me to insert any further publication data. Please read my author name only as “Fraleoni A”, and consider this fact in case of checks using the main search engines, where if you want to find all of my indexed works you must search for “Fraleoni” as author, instead of “Fraleoni Morgera”. This latter search would recover only 24 publications out of my actual 31 ones. ORAL CONTRIBUTION (PLEASE TAKE NOTICE THAT THIS CONTRIBUTION WAS BROUGHT TO THE CONFERENCE AS BOTH A POSTER AND A TALK - “Structure-property correlations of poly(3-alkyl)thiophenes having a chromophoric group as side chain” - PRESENTING AUTHOR
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