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Molecular engineering of side chain liquid crystalline polymers exhibiting a chiral smectic C phase

Zheng, Qiang

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1994, Doctor of Philosophy, Case Western Reserve University, Macromolecular Science.
This dissertation is concerned with the synthesis and characterization of side chain liquid crystalline polymers (LCPs) exhibiting a chiral smectic ( SC*) phase. Three problems have been investigated: (1) molecular design of linear side chain LCPs via living cationic polymerization of mesogenic vinyl ethers containing a chiral center; (2) molecular design of liquid crystalline elastomers via living cationic copolymerization of mesogenic vinyl ethers with a nonmesogenic bifunctional monomer containing both vinyl ether and methacryloyl groups; (3) investigation of chiral molecular recognition in molecular and macromolecular pairs of enantiomers. In the first part of this dissertation the synthesis and characterization of linear side chain LCPs exhibiting a SC* phase by living cationic polymerization and copolymerization of (S)-2-methylbutyl 4′-(ω-vinyloxyalkyloxy)biphenyl-4-carboxylate (14-n) with undecanyl, octyl and hexyl groups (n = 11, 8 and 6) and (2S, 3S)-2-chloro-3-methylpentyl 4′-(ω-vinyloxyalkyloxy)biphenyl-4-carboxylate (15-n) with undecanyl, octyl, hexyl, propyl and ethyl groups (n = 11, 8, 6, 3 and 2) are presented. The influence of various structural parameters (such as molecular weight, spacer length, copolymer composition, and the type of chiral tail groups) on the mesomorphic behavior of the resulting polymers and copolymers is discussed. The presence of -Cl in the chiral tail group of 15-n leads to polymers containing shorter spacer exhibiting SC* phase and the resulting polymers show higher thermal stability of SC* phase, however, the range of SC* phase was reduced if compared with the corresponding poly(14-n). By cationic copolymerization, side chain LCPs exhibiting a SC* phase from below room temperature up to 90° C were obtained. In Part II we described a novel synthetic procedure for the preparation of well defined thermally reactive side chain LCPs, which can become liquid crystalline elastomers upon thermal or photo treatment. This procedure consists of the living cationic copolymerization of a mesogenic vinyl ether with a nonmesogenic bifunctional monomer containing both vinyl ether and methacryloyl groups. It is shown that a shorter spacer in the reactive bifunctional monomer leads to networks with broader range of mesomorphism and less ability of crystallization than those derived from a reactive monomer containing a spacer length equal to that of the mesogenic monomer. In Part III we will present the results on the investigation of chiral molecular recognition in molecular and macromolecular pairs of (R)- and (S)-1-cyano-2-methylpropyl 4'-[4-(8-vinyloxyoctyloxy)benzoyl] oxy)biphenyl-4-carboxylate enantiomers. Both monomers exhibit enantiotropic SA, SC* and SX phases on second heating and cooling scans. The corresponding homopolymers exhibit enantiotropic SA and SC* phases. The homopolymers with DP < 6 show also a crystalline phase, while those with DP > 10 exhibit a second SX phase. Mesomorphic behavior in various binary enantiomeric mixtures is discussed as a function of chirality. Chiral molecular recognition was observ ed in the SA and SX phases of monomers but not in the SA phase of polymers. (Abstract shortened by UMI.)
Virgil Percec (Advisor)
274 p.

Recommended Citations

Citations

  • Zheng, Q. (1994). Molecular engineering of side chain liquid crystalline polymers exhibiting a chiral smectic C phase [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1057695554

    APA Style (7th edition)

  • Zheng, Qiang. Molecular engineering of side chain liquid crystalline polymers exhibiting a chiral smectic C phase. 1994. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1057695554.

    MLA Style (8th edition)

  • Zheng, Qiang. "Molecular engineering of side chain liquid crystalline polymers exhibiting a chiral smectic C phase." Doctoral dissertation, Case Western Reserve University, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=case1057695554

    Chicago Manual of Style (17th edition)