Constitutional isomeric effect on the dielectric relaxation of a nematic liquid crystalline polymethacrylate containing a methoxymethylstilbene side group

Autor:	W. L. Gordon, D. E. Schuele, S. W. Smith, Z. Z. Zhong
Rok vydání:	1993
Předmět:	chemistry.chemical_classification Polymers and Plastics Chemistry Organic Chemistry Polymer Activation energy Dielectric Inorganic Chemistry Liquid crystal Materials Chemistry Side chain Relaxation (physics) Physical chemistry Organic chemistry Pendant group Glass transition
Zdroj:	Macromolecules. 26:6403-6409
ISSN:	1520-5835 0024-9297
DOI:	10.1021/ma00076a016
Popis:	Broad band frequency (0.1 Hz-10 MHz) dielectric relaxation spectroscopy has been utilized to investigate nematic liquid crystalline polymethacrylates [CH 2 C(CH 3 )(COO[CH 2 ] 6 OPhCR=CR'PhOMe)] n (R= H, R'= Me, 4-6-PMA; R= Me, R'= H, 4'-6-PMA). While 4-6-PMA shows two typical relaxation process in a side-chain liquid crystalline polymer system, 4'-6-PMA essentially has one relaxation process. The temperature-dependent relaxation times, obtained through Havriliak-Negami data fitting, show «kinks» near calorimetric nematic-isotropic transition and a non-Arrhenius characteristic toward the glass transition. The glass behavior has been fitted with a Vogel-Fulcher-Tammann-Hesse (VFTH) equation and a general formula for activation energy has been derived in terms of VFTH parameters
Databáze:	OpenAIRE
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