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Synthesis and Characterization of Poly(9,9-Dihexylfluorene-mb-methylene)s

Copenhafer, James Edward (2007) Synthesis and Characterization of Poly(9,9-Dihexylfluorene-mb-methylene)s. Doctoral Dissertation, University of Pittsburgh.

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    Abstract

    The synthesis and characterization of copolymers possessing exact repeating sequences of 9,9-dihexylfluorene and methylene repeat units are described. Each poly(9,9-dihexylfluorene-mb-methylene) (PFM, mb = multiblock) was synthesized following the assembly of a symmetrically disubstituted monodisperse oligofluorene. Alkyl segments possessing terminal alkene functionality were then coupled at both of the substituted positions on the oligofluorene to give a macromolecular "segmer" compound. Each segmer was polymerized using Acyclic Diene Metathesis (ADMET) and, following post-polymerization hydrogenation, a PFM with an entirely repeating diblock sequence was produced. PFMs possessing 9,9-dihexylfluorene segment lengths of x = 1, 2, 3, 4, 7, or 8 units and methylene segment lengths of y = 10 or 18 units were prepared to give a ten member PFM library. As PFMs have exact chemical compositions and monomer unit sequencing, studies aimed at elucidating solution and bulk phase trends were performed. Spectroscopic characteristics that make polyfluorene-type materials attractive include their generally efficient blue light emission (λmax ~ 448 nm). Successful investigations into the optical tuning of PFMs in solution and in the bulk are described. Additionally, thermal- and photostabilities of PFMs under a variety of conditions are reported and compared to the related homopolymer, poly(9,9-dihexylfluorene) [PDHF]. Compared to PDHF, PFMs display similar, and in some cases superior resistance to photobleaching processes. Additionally, thermal and photostability investigations into keto-induced degradation processes of PFMs suggest that interruption of the fluorene segments with alkyl spacers effectively suppresses intrachain charge migration and interchain Förster energy transfer in the bulk. The rate of PFM, and likewise PDHF degradation was found to be at least partially dependent on the initial state of the sample.Efforts toward the transition metal-catalyzed production of cyclic oligomers are described. Two rigid bifunctional molecules bearing both transition-metal metathesis initiating and terminating groups were prepared. The synthesis and metathesis activity of these compounds are reported.


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    Item Type: University of Pittsburgh ETD
    Creators/Authors:
    CreatorsEmailORCID
    Copenhafer, James Edwardj1e1c1@yahoo.com
    ETD Committee:
    ETD Committee TypeCommittee MemberEmailORCID
    Committee ChairMeyer, Taratmeyer@pitt.edu
    Committee MemberBeckman, Ericbeckman@engr.pitt.edu
    Committee MemberPetoud, Stephanespetoud@pitt.edu
    Committee MemberChapman, Tobytchapman@pitt.edu
    Title: Synthesis and Characterization of Poly(9,9-Dihexylfluorene-mb-methylene)s
    Status: Unpublished
    Abstract: The synthesis and characterization of copolymers possessing exact repeating sequences of 9,9-dihexylfluorene and methylene repeat units are described. Each poly(9,9-dihexylfluorene-mb-methylene) (PFM, mb = multiblock) was synthesized following the assembly of a symmetrically disubstituted monodisperse oligofluorene. Alkyl segments possessing terminal alkene functionality were then coupled at both of the substituted positions on the oligofluorene to give a macromolecular "segmer" compound. Each segmer was polymerized using Acyclic Diene Metathesis (ADMET) and, following post-polymerization hydrogenation, a PFM with an entirely repeating diblock sequence was produced. PFMs possessing 9,9-dihexylfluorene segment lengths of x = 1, 2, 3, 4, 7, or 8 units and methylene segment lengths of y = 10 or 18 units were prepared to give a ten member PFM library. As PFMs have exact chemical compositions and monomer unit sequencing, studies aimed at elucidating solution and bulk phase trends were performed. Spectroscopic characteristics that make polyfluorene-type materials attractive include their generally efficient blue light emission (λmax ~ 448 nm). Successful investigations into the optical tuning of PFMs in solution and in the bulk are described. Additionally, thermal- and photostabilities of PFMs under a variety of conditions are reported and compared to the related homopolymer, poly(9,9-dihexylfluorene) [PDHF]. Compared to PDHF, PFMs display similar, and in some cases superior resistance to photobleaching processes. Additionally, thermal and photostability investigations into keto-induced degradation processes of PFMs suggest that interruption of the fluorene segments with alkyl spacers effectively suppresses intrachain charge migration and interchain Förster energy transfer in the bulk. The rate of PFM, and likewise PDHF degradation was found to be at least partially dependent on the initial state of the sample.Efforts toward the transition metal-catalyzed production of cyclic oligomers are described. Two rigid bifunctional molecules bearing both transition-metal metathesis initiating and terminating groups were prepared. The synthesis and metathesis activity of these compounds are reported.
    Date: 29 January 2007
    Date Type: Completion
    Defense Date: 06 November 2006
    Approval Date: 29 January 2007
    Submission Date: 29 October 2006
    Access Restriction: 5 year -- Restrict access to University of Pittsburgh for a period of 5 years.
    Patent pending: No
    Institution: University of Pittsburgh
    Thesis Type: Doctoral Dissertation
    Refereed: Yes
    Degree: PhD - Doctor of Philosophy
    URN: etd-10292006-104853
    Uncontrolled Keywords: OLED; polymer
    Schools and Programs: Dietrich School of Arts and Sciences > Chemistry
    Date Deposited: 10 Nov 2011 15:03
    Last Modified: 08 May 2012 11:39
    Other ID: http://etd.library.pitt.edu/ETD/available/etd-10292006-104853/, etd-10292006-104853

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