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Theory of polyvinylidene fluoride and its ferroelectric random copolymers

Zhang, Renshi

Abstract Details

1991, Doctor of Philosophy, Case Western Reserve University, Physics.
In this thesis a structural analysis of polyvinylidene fluoride is presented by calculation of the intrachain and interchain interactions. The compactness of chain packing and the condition of commensurability are included in the discussion to show how interchain energy acts to make the α phase the stable structure. The possibility of the existence and formation of a 31 helix under special conditions is discussed. A general formalism that uses functionals of the torsional angle distribution for the free energy is described. This general formalism is then applied to a simple three-state model of random copolymers of vinylidene fluoride with tetrafluoroethylene. Because both vinylidene fluoride and tetrafluoroethylene monomers are tacticity-symmetric, we make the further approximation of allowing the gauche′ bond to be degenerate with the gauche bond. We successfully find a first-order ferroelectric-to-paraelectric transition in polyvinylidene fluoride and also find that the ferroelectric phase in copolymers with tetrafluoroethylene is preserved at high temperatures. The nearly-all-trans phase of pure polytetrafluoroethylene does not change phase even at high temperatures. All these findings are in agreement with experiment. A drawback of this model is that it contains only one order pa rameter. As a result, we cannot predict at the same time both a ferroelectric-to-paraelectric transition and the melting transition, which both exist in the random copolymers. We examine the role of the intrachain Coulomb interactions in the ferroelectric and paraelectric phases, and propose that copolymers of vinylidene fluoride with ethylene should be ferroelectric.
Philip Taylor (Advisor)
111 p.

Recommended Citations

Citations

  • Zhang, R. (1991). Theory of polyvinylidene fluoride and its ferroelectric random copolymers [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1055948034

    APA Style (7th edition)

  • Zhang, Renshi. Theory of polyvinylidene fluoride and its ferroelectric random copolymers. 1991. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1055948034.

    MLA Style (8th edition)

  • Zhang, Renshi. "Theory of polyvinylidene fluoride and its ferroelectric random copolymers." Doctoral dissertation, Case Western Reserve University, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=case1055948034

    Chicago Manual of Style (17th edition)