1,720,996 research outputs found
New regioregular polythiophenes functionalized with sulfur-containing substituents for bulk heterojunction solar cells
No full textOrganic photovoltaic devices fabricated with polythiophenic derivatives and single-walled carbon nanotubes
(SWCNT)s have been assembled and tested. For this purpose, some new regioregular polythiophenes
with different sulfur-containing groups in the terminal position of a hexamethylenic side chain
were prepared using direct and indirect polymerization routes. The optical features of the synthesized
polymers were examined and compared by registering their UV–Vis spectra in different solvent/non-solvent
systems and in film; their thermal stability, electrical conductivity, cyclic voltammetry and photovoltaic
properties were carefully analyzed. In particular, the two samples bearing the sulfinyl group in
side chain showed better chromic responses, enhanced self-assembling capabilities, more extended conjugation
length, higher electrical conductivity and very promising photovoltaic performances, when compared
to those of analogous systems reported on up to now
Effects of polar additives on the anionic polymerization of 1,3-butadiene and styrene
No full textThe homopolymerization of butadiene and copolymerization
of styrene with butadiene were performed
using n-butyllithium as the initiator, cyclohexane as a solvent
and some new ethers (σ-ligands) as active centers
modifiers. The modifiers were synthesized using an elegant
synthetic route starting from a commercial precursor,
and high yields were obtained. Their addition in the
homopolymerization of butadiene strongly influences the
vinyl content and reduces the polydispersity of the obtained
polymer. The modifiers are also able to change the
reactivity ratios in the styrene-butadiene copolymerization,
leading to an appreciable randomizing effect. The
modifiers also show a high activity, since their addition
in a very low amount is able to strongly modify the progress
in the reaction of anionic polymerization
Synthesis, characterization and optical properties of a regioregular and soluble poly[3-(10-hydroxydecyl)-2,5-thienylene]
No full textThe preparation of a regioregular trimethylsilanyloxydecyl 3-substituted polythiophene and its conversion to the corresponding
hydroxydecyl polymer, which is soluble in common organic solvents, is described both in solution and in film. The chromic behaviour of the
hydroxy functionalized polymer was investigated by UV–vis spectroscopy in different solvent/non-solvent mixtures and in the solid state by
exposing the polymer adsorbed on hydroxylic matrices to methanol vapours
Synthesis and characterization of a highly soluble poly[3-(10-hydroxydecyl) thiophene]
No full textThe preparation of a regioregular HH-TT linked poly[3-(10-hexanoyloxy) decyl]thiophene and its conversion to the corresponding hydroxy-functionalized polymer is described and discussed. The hydroxydecyl polymer, highly soluble in common organic solvents, has been characterized via NMR, FT-IR, DSC and X-ray diffractometry
Facile Synthesis of Soluble Multifunctional Polyalkylthiophenes
No full textA method of synthesis leading to poly(3-alkylthiophene)s with two different functional groups in the side chain, one of which is an NLO-active chromophore, has been developed. This method, based on the post-functionalization of a reactive homopolymeric precursor, permits to prepare different polyfunctional polymers that are fully soluble in the most commonly used organic solvents. The procedure is very easy to perform, cost-effective, highly versatile and reproducible
Synthesis and characterization of poly(3-alkylthiophenes) with NLO chromophoric groups in side chains
No full textPolythiophene copolymers containing alkyl side chains of different length and partially functionalized with chromophoric groups have been synthesized by FeCl3 oxidative coupling of 3-alkylthiophenes and functionalized 3-alkylthiophenes. Composition, molecular weight and configuration of the soluble fraction of the copolymers have been investigated and some structure-property correlations have been evidenced
Facile Synthesis of Soluble Multifunctional Polyalkylthiophenes
No full textA method of synthesis leading to
poly(3-alkylthiophene)s with two different functional
groups in the side chain, one of which is an NLO-active
chromophore, has been developed. This method, based on
the post-functionalization of a reactive homopolymeric
precursor, permits to prepare different polyfunctional
polymers that are fully soluble in the most commonly
used organic solvents. The procedure is very easy to perform,
cost-effective, highly versatile and reproducible
A new thiophene-copolymer with side-chain LC mesogen group for efficient BHJ solar cells
No full textThe control of structure and morphology of the photoactive blend is a fundamental prerequisite for the obtainment of high efficiency values in bulk heterojunction (BHJ) polymeric solar cells. In fact, the presence of disordered amorphous structures in BHJ cells leads to charge recombination, thus reducing the performance of the final device. A new thiophene copolymer functionalized in the side chain with a liquid crystalline (LC) group, poly(3-hexylthiophene)-co-3[6-(4-cyanodiphenyloxy)hexyl]thiophene, has been synthesized in order to induce microphase separation when the conjugated electron donor polymer is mixed with the acceptor PCBM in the photoactive blend. Due to its good solubility in common organic solvents, the LC-copolymer has been fully characterized using spectroscopic, thermal and electronic techniques. The results suggest that, upon suitable annealing procedure, the LC-copolymer spontaneously assembles in a highly ordered structure which favors a nano-dispersed aggregation of the PCBM molecules, thus allowing to achieve a power conversion efficiency near to 6%
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
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