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Complex Formation between a Fluorescently-Labeled Polyelectrolyte and a Tribloc...
Costa, Telma; Melo, J. Seixas de; Miguel, Maria da G.; Lindman, Björn; Schillén, KarinThe association between a randomly pyrene labeled PAA polymer (PAAMePy55) and a PEO−PPO−PEO triblock copolymer (P123) in aqueous solutions of different NaCl concentrations and pHs has been studied by means of dynamic light scattering (DLS) and steady-state fluorescence spectroscopy at 40 °C. At acidic pH values, in the low P123/PAAMePy55 molar ratio regime (i.e., at low P123 concentrations), the relaxation time...
Association of a Hydrophobically Modified Polyelectrolyte and a Block Copolymer...
Costa, Telma; Schillén, Karin; Miguel, Maria da G.; Lindman, Björn; Melo, J. Seixas deBy using absorption and fluorescence (steady-state and time-resolved) techniques, the interaction between a poly(acrylic acid) (PAA), randomly grafted with pyrene (Py) units (PAAMePy55), and a triblock copolymer of poly(ethylene oxide) and poly(propylene oxide) (EO20PO68EO20, P123) was investigated. From the fluorescence data, it is shown that upon addition of P123 a decrease of the (pyrene−pyrene, Py−Py) intra...
Alternating Binaphthyl−Thiophene Copolymers: Synthesis, Spectroscopy, and Photo...
Pina, J.; Melo, J. Seixas de; Burrows, H. D.; Maçanita, A. L.; Galbrecht, F.; Bünnagel, T.; Scherf, U.The synthesis and a comprehensive spectroscopic and photophysical study are presented of four alternating binaphthyl−oligothiophene copolymers (DP: 10−15 repeat units) in solution at room and low temperature and in the solid state (thin films). Detailed results are presented on absorption, emission, and triplet−triplet absorption spectra together with all relevant quantum yields (fluorescence, intersystem cross...
A comprehensive study of the spectral and photophysical properties of arylthiop...
Melo, J. Seixas de; Pina, J.; Rodrigues, L. M.; Becker, R. S.A series of conjugated oligomers with rigid (fused-ring) structure, consisting in different polycyclic aromatic hydrocarbons (PAHs) possessing a single thiophene unit, here designated as arylthiophenes, were investigated in solution. For presentation clarity, the compounds were organized in two different groups. The first group includes the compounds where one, two, three and four benzene rings are added to a t...
Excited State Properties of Oligophenyl and Oligothienyl Swivel Cruciforms
Pina, J.; Melo, J. Seixas de; Burrows, H. D.; Galbrecht, F.; Bilge, A.; Kudla, C. J.; Scherf, U.A comprehensive study has been undertaken of the electronic spectral and photophysical properties of two oligophenyl (BPH and BPHF) and one oligothienyl (BTF) swivel cruciforms involving measurements of absorption, fluorescence, and phosphorescence spectra, quantum yields of fluorescence (phiF), phosphorescence (phiPh) and triplet formation (phiT), lifetimes of fluorescence (τF) and of the triplet state (τT), a...
Spectral and Photophysical Studies of Poly[2,6-(1,5-dioctylnaphthalene)]thiophenes
Pina, J.; Melo, J. Seixas de; Burrows, H. D.; Galbrecht, F.; Nehls, B. S.; Farrell, T.; Scherf, U.A complete spectroscopic and photophysical study of three alternating naphthalene-α-thiophene copolymers was undertaken in solution (room and low temperature) and in the solid state (thin films in a Zeonex matrix). The study comprises absorption, emission, and triplet−triplet spectra together with quantitative measurements of quantum yield (fluorescence, intersystem-crossing, internal conversion, and singlet ox...
Interplay of Electrostatic and Hydrophobic Effects with Binding of Cationic Gem...
Burrows, Hugh D.; Tapia, María J.; Silva, Cláudia L.; Pais, Alberto A. C. C.; Fonseca, Sofia M.; Pina, João; Melo, J. Seixas de; Wang, YujieUnderstanding factors responsible for the fluorescence behavior of conjugated polyelectrolytes and modulation of their behavior are important for their application as functional materials. The interaction between the anionic poly1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)]fluorene-2,7-diylcopolymer (PBS−PFP) and cationic gemini surfactants α,ω-(CmH2m+1N+(CH3)2)2(CH2)s(Br-)2 (m-s-m; m = 12, s = 2, 3, 5, 6, ...
Electronic spectral and photophysical properties of some p-phenylenevinylene ol...
Melo, J. Seixas de; Pina, J.; Burrows, H. D.; Di Paolo, R. E.; Maçanita, A. L.A comprehensive photophysical and spectroscopic study of a new class of p-phenylenevinylene oligomers (PPV-trimers) possessing different alkyl and alkyloxy sidechain substituents and different end groups (aldehyde, CC, phenylene and anthracene units) was undertaken in solution at room temperature (293 K), low temperature (77 K) and in thin films. The study comprises absorption, emission and triplet-triplet abso...
Photophysical Studies of α,ω-Dicyano-oligothiophenes NC(C4H2S)nCN (n = 1−6)
Pina, J.; Burrows, H. D.; Becker, R. S.; Dias, F. B.; Maçanita, A. L.; Melo, J. Seixas deThe photophysics of six oligothiophenes end-capped with cyano groups (CNαn) was investigated in solution at room and low temperature. The study comprises singlet−singlet and triplet−triplet absorption and emission spectra together with lifetimes and quantum yields for all the radiative and nonradiative processes. From the lifetimes and quantum yields, it was possible to extract the rate constants for all the pr...
Triplet-State and Singlet Oxygen Formation in Fluorene-Based Alternating Copoly...
Fonseca, S. M.; Pina, J.; Arnaut, L. G.; Melo, J. Seixas de; Burrows, H. D.; Chattopadhyay, N.; Alcácer, L.; Charas, A.; Morgado, J.; Monkman, A. P.Data are reported on the triplet states of a series of fluorene-based A-alt-B type alternating copolymers based on pulse radiolysis-energy transfer and flash photolysis experiments. From the pulse radiolysis experiments, spectra are given for eight copolymers involving phenylene, thiophene, benzothiadiazole, and oligothienylenevinylene groups. Quantum yields for triplet-state formation (ΦT) have been obtained b...
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