Kinetics and thermodynamics of poly (9,9-dioctylfluorene) beta-phase formation in dilute solution
Autor(a) principal: | |
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Data de Publicação: | 2006 |
Outros Autores: | , , , , |
Tipo de documento: | Artigo |
Idioma: | eng |
Título da fonte: | Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
Texto Completo: | http://hdl.handle.net/10400.2/1950 |
Resumo: | Poly(9,9-dioctylfluorene) (PFO) adopts a particular type of conformation in dilute solutions of the poor solvent methylcyclohexane (MCH) below 273 K, which is revealed by the appearance of a red-shifted absorption peak at 437−438 nm. The formation of this ordered conformation depends on the temperature but is independent of polymer concentration over the range studied (3−25 μg/mL). On the basis of absorption, steady-state, and time-resolved fluorescence data, the new absorption peak at 437−438 nm is assigned to a highly ordered conformation of PFO chains, analogous to the so-called β-phase first identified in PFO films. From the study of PFO solutions in MCH as a function of temperature, we conclude that these ordered segments (β-conformation) coexist with less ordered domains in the same chain. When the ordered domains are present, they act as efficient energy traps and the fluorescence from the disordered regions is quenched. The transition between the disordered and the ordered PFO conformations is adequately described by a mechanism that involves two steps: a first, essentially intramolecular, one from a relatively disordered (α) to an ordered conformation (β), followed by aggregation of chains containing β-conformation into anisotropic ordered domains. From the temperature dependence of the 437−438 nm peak intensity, the transition temperature Tβ = 261 K, enthalpy ΔHβ = −18.0 kcal mol-1, and entropy ΔSβ = −68.4 cal K-1 mol-1 were obtained. The formation of the β-conformation domains were also followed as a function of time at 260 K. The rate constants at 260 K were determined, showing an order of magnitude around 10-3 s-1 (kα→β = 5.9 × 10-4 s-1; kβ→α = 9 × 10-4 s-1; kagg = 2.3 × 10-3 M-1 s-1; kdiss = 4.4 × 10-4 s-1). This small magnitude explains the long times required for a “complete” conversion to the β-conformation. |
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Kinetics and thermodynamics of poly (9,9-dioctylfluorene) beta-phase formation in dilute solutionPoly(9,9-dioctylfluorene) beta-PhaseKinetic propertiesThermodynamic propertiesSynthetic high polymersPoly(9,9-dioctylfluorene) (PFO) adopts a particular type of conformation in dilute solutions of the poor solvent methylcyclohexane (MCH) below 273 K, which is revealed by the appearance of a red-shifted absorption peak at 437−438 nm. The formation of this ordered conformation depends on the temperature but is independent of polymer concentration over the range studied (3−25 μg/mL). On the basis of absorption, steady-state, and time-resolved fluorescence data, the new absorption peak at 437−438 nm is assigned to a highly ordered conformation of PFO chains, analogous to the so-called β-phase first identified in PFO films. From the study of PFO solutions in MCH as a function of temperature, we conclude that these ordered segments (β-conformation) coexist with less ordered domains in the same chain. When the ordered domains are present, they act as efficient energy traps and the fluorescence from the disordered regions is quenched. The transition between the disordered and the ordered PFO conformations is adequately described by a mechanism that involves two steps: a first, essentially intramolecular, one from a relatively disordered (α) to an ordered conformation (β), followed by aggregation of chains containing β-conformation into anisotropic ordered domains. From the temperature dependence of the 437−438 nm peak intensity, the transition temperature Tβ = 261 K, enthalpy ΔHβ = −18.0 kcal mol-1, and entropy ΔSβ = −68.4 cal K-1 mol-1 were obtained. The formation of the β-conformation domains were also followed as a function of time at 260 K. The rate constants at 260 K were determined, showing an order of magnitude around 10-3 s-1 (kα→β = 5.9 × 10-4 s-1; kβ→α = 9 × 10-4 s-1; kagg = 2.3 × 10-3 M-1 s-1; kdiss = 4.4 × 10-4 s-1). This small magnitude explains the long times required for a “complete” conversion to the β-conformation.American Chemical SocietyRepositório AbertoCosta, Fernando Pestana daMaçanita, António L.Morgado, JorgeDias, Fernando B.Burrows, Hugh D.Monkman, Andrew P.2011-11-07T18:01:52Z2006-082006-08-01T00:00:00Zinfo:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/articleapplication/pdfhttp://hdl.handle.net/10400.2/1950engCosta, Fernando Pestana da [et al.] - Kinetics and thermodynamics of poly (9,9-dioctylfluorene) beta-phase formation in dilute solution. "Macromolecules" [Em linha]. ISSN 0024-9297 (Print) 1520-5835 (Online). Vol. 39, nº 17 (2006), p. 5854-5864(Print Edition) 0024-9297info:eu-repo/semantics/openAccessreponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãoinstacron:RCAAP2023-11-16T15:15:07Zoai:repositorioaberto.uab.pt:10400.2/1950Portal AgregadorONGhttps://www.rcaap.pt/oai/openaireopendoar:71602024-03-19T22:43:35.643883Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãofalse |
dc.title.none.fl_str_mv |
Kinetics and thermodynamics of poly (9,9-dioctylfluorene) beta-phase formation in dilute solution |
title |
Kinetics and thermodynamics of poly (9,9-dioctylfluorene) beta-phase formation in dilute solution |
spellingShingle |
Kinetics and thermodynamics of poly (9,9-dioctylfluorene) beta-phase formation in dilute solution Costa, Fernando Pestana da Poly(9,9-dioctylfluorene) beta-Phase Kinetic properties Thermodynamic properties Synthetic high polymers |
title_short |
Kinetics and thermodynamics of poly (9,9-dioctylfluorene) beta-phase formation in dilute solution |
title_full |
Kinetics and thermodynamics of poly (9,9-dioctylfluorene) beta-phase formation in dilute solution |
title_fullStr |
Kinetics and thermodynamics of poly (9,9-dioctylfluorene) beta-phase formation in dilute solution |
title_full_unstemmed |
Kinetics and thermodynamics of poly (9,9-dioctylfluorene) beta-phase formation in dilute solution |
title_sort |
Kinetics and thermodynamics of poly (9,9-dioctylfluorene) beta-phase formation in dilute solution |
author |
Costa, Fernando Pestana da |
author_facet |
Costa, Fernando Pestana da Maçanita, António L. Morgado, Jorge Dias, Fernando B. Burrows, Hugh D. Monkman, Andrew P. |
author_role |
author |
author2 |
Maçanita, António L. Morgado, Jorge Dias, Fernando B. Burrows, Hugh D. Monkman, Andrew P. |
author2_role |
author author author author author |
dc.contributor.none.fl_str_mv |
Repositório Aberto |
dc.contributor.author.fl_str_mv |
Costa, Fernando Pestana da Maçanita, António L. Morgado, Jorge Dias, Fernando B. Burrows, Hugh D. Monkman, Andrew P. |
dc.subject.por.fl_str_mv |
Poly(9,9-dioctylfluorene) beta-Phase Kinetic properties Thermodynamic properties Synthetic high polymers |
topic |
Poly(9,9-dioctylfluorene) beta-Phase Kinetic properties Thermodynamic properties Synthetic high polymers |
description |
Poly(9,9-dioctylfluorene) (PFO) adopts a particular type of conformation in dilute solutions of the poor solvent methylcyclohexane (MCH) below 273 K, which is revealed by the appearance of a red-shifted absorption peak at 437−438 nm. The formation of this ordered conformation depends on the temperature but is independent of polymer concentration over the range studied (3−25 μg/mL). On the basis of absorption, steady-state, and time-resolved fluorescence data, the new absorption peak at 437−438 nm is assigned to a highly ordered conformation of PFO chains, analogous to the so-called β-phase first identified in PFO films. From the study of PFO solutions in MCH as a function of temperature, we conclude that these ordered segments (β-conformation) coexist with less ordered domains in the same chain. When the ordered domains are present, they act as efficient energy traps and the fluorescence from the disordered regions is quenched. The transition between the disordered and the ordered PFO conformations is adequately described by a mechanism that involves two steps: a first, essentially intramolecular, one from a relatively disordered (α) to an ordered conformation (β), followed by aggregation of chains containing β-conformation into anisotropic ordered domains. From the temperature dependence of the 437−438 nm peak intensity, the transition temperature Tβ = 261 K, enthalpy ΔHβ = −18.0 kcal mol-1, and entropy ΔSβ = −68.4 cal K-1 mol-1 were obtained. The formation of the β-conformation domains were also followed as a function of time at 260 K. The rate constants at 260 K were determined, showing an order of magnitude around 10-3 s-1 (kα→β = 5.9 × 10-4 s-1; kβ→α = 9 × 10-4 s-1; kagg = 2.3 × 10-3 M-1 s-1; kdiss = 4.4 × 10-4 s-1). This small magnitude explains the long times required for a “complete” conversion to the β-conformation. |
publishDate |
2006 |
dc.date.none.fl_str_mv |
2006-08 2006-08-01T00:00:00Z 2011-11-07T18:01:52Z |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
dc.type.driver.fl_str_mv |
info:eu-repo/semantics/article |
format |
article |
status_str |
publishedVersion |
dc.identifier.uri.fl_str_mv |
http://hdl.handle.net/10400.2/1950 |
url |
http://hdl.handle.net/10400.2/1950 |
dc.language.iso.fl_str_mv |
eng |
language |
eng |
dc.relation.none.fl_str_mv |
Costa, Fernando Pestana da [et al.] - Kinetics and thermodynamics of poly (9,9-dioctylfluorene) beta-phase formation in dilute solution. "Macromolecules" [Em linha]. ISSN 0024-9297 (Print) 1520-5835 (Online). Vol. 39, nº 17 (2006), p. 5854-5864 (Print Edition) 0024-9297 |
dc.rights.driver.fl_str_mv |
info:eu-repo/semantics/openAccess |
eu_rights_str_mv |
openAccess |
dc.format.none.fl_str_mv |
application/pdf |
dc.publisher.none.fl_str_mv |
American Chemical Society |
publisher.none.fl_str_mv |
American Chemical Society |
dc.source.none.fl_str_mv |
reponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação instacron:RCAAP |
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Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
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Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
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Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação |
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