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Molecular engineering of liquid crystal polymers by living polymerization

Lee, Myongsoo
http://rave.ohiolink.edu/etdc/view?acc_num=case1060091978

Abstract Details

1992, Doctor of Philosophy, Case Western Reserve University, Macromolecular Science.
This dissertation is concerned with the synthesis and living cationic polymerization of ω-((4-cyano-4′-biphenyl)oxy) alkyl vinyl ethers with alkyl groups from two to eleven methylene units. The phase transitions of polymers are described and compared to those of the ω((4-cyano-4′-biphenyl)oxy) alkyl ethyl ethers which are models of the monomeric structural units of the corresponding polymers. Polymers containing flexible spacers with either 11 or 10 methylene unit exhibit an enantiotropic s A phase, and above a certain molecular weight both polymers show a second smectic (s X, unidentified) phase. Polymers with either 6 or 8 methylene units exhibit nematic and s A phases at low degrees of polymerization. However, above a certain molecular weight the nematic phase disappears and a second smectic phase (s X) appears. Polymers with medium length spacers containing an odd number of methylene units (n = 7,9) exhibit an enantiotropic s A phase and polymers with spacer lengths (n = 3 and 4) exhibit an enantiotropic nematic mesophase irrespective of molecular weight. Results demonstrate that the transition temperature, nature, and number of mesophases are molecular weight dependent. In the second part, the synthesis and characte rization of statistical binary copolymers based on ω-((4-cyano-4′-biphenyl)oxy) alkyl vinyl ethers with different spacer lengths are described. It is demonstrated that the structural units of all binary copolymers behave as an ideal solution. This behavior allows the molecular engineering of materials having specified phase transition temperatures and corresponding thermodynamic parameters in a straightforward manner by living copolymerizations The synthesis and characterization of polyω-((4-cyano-4′-biphenyl)oxy) alkyl vinyl ether-co-(2S,3S)-(+)-2-chloro-3-methylpentyl 4′-(8-vinyloxyoctyloxy)biphenyl-4-carboxylateX/Y poly((6-n)-co-(15-8)) X/Y (where X/Y represents the molar ratio of the two structural units) with constant degree of polymerization and narrow molecular weight distribution are also described. In Part III, the synthesis and characterization of macromonomers and block copolymers based on mesogenic units are described. All of block copolymers are shown to possess a microphase separated morphology by their thermal behavior, as determined with DSC and optical polarized microscopy. (Abstract shortened with permission of author.)
Virgil Percec (Advisor)
401 p.
Chemistry, Polymer
Liquid crystal polymers; Living polymerization

Recommended Citations

Citations

  • Lee, M. (1992). Molecular engineering of liquid crystal polymers by living polymerization [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1060091978

    APA Style (7th edition)

  • Lee, Myongsoo. Molecular engineering of liquid crystal polymers by living polymerization. 1992. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1060091978.

    MLA Style (8th edition)

  • Lee, Myongsoo. "Molecular engineering of liquid crystal polymers by living polymerization." Doctoral dissertation, Case Western Reserve University, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=case1060091978

    Chicago Manual of Style (17th edition)

case1060091978
706
© 1992, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.