An intensive study has been conducted to map the director fields of disclination of nematic liquid crystalline copolyesters.In this study,films of two wholly aromatic main-chain polyesters containing para- (AB A/MH/ TFTA) and meta-linkages (ABA/MH/TFIA) (ABA,p-acetoxybenzoic acid;MH,maleic hydrazine;TFTA,tetrafluoroterephthalic acid;TFIA,tetrafluoroisophthalic acid) were synthesized to investigate the effects of kinks on liquid crystallinity,disclination strength (S),and surface microcracks decoration.These two copolyesters were prepared by in-situ thin film polymerization and characterized by polarizing light microscope,wide-angle X-ray diffraction,as well as "rotational isomeric states" (RIS) Metropolis Monte Carlo (RMMC) simulation.An optical microscope shows that the surface microcracks forms in the nematic-mosaic texture during a rapid quenching.The ABA/MH/TFTA film exhibits disclination strength with S - +1 and S = - 1/2;however,disclination strengths with S = +- 1 have been observed in the ABA/MH/TFIA system.To our best knowledge,this is the first paper reporting the effects and evidence of kink (meta and para moieties) on topological defect of disclination.In addition,the RMMC analysis supports the liquid crystal formation in both polyester films with a persistence ratio greater than 6.42.
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Department of Chemical and Biomolecular Engineering,National University of Singapore,and Institute of Materials Research and Engineering,3 Research Link,Singapore 117602;
