Dielectric properties of single crystals of the substituted diacetylene pTS: effect of the solid-state polymerization and phase transitions |
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| Affiliation: | 1. Alexander Butlerov Institute of Chemistry, Kazan Federal University, 18 Kremlevskaya Street, Kazan 420008, Russian Federation;2. Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences, 8 Arbuzov Street, Kazan 420088, Russian Federation;3. Department of Chemistry, University of Alabama at Birmingham, 901 S. 14th Street, Birmingham, AL 35294, USA |
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| Abstract: | Dielectric permittivities of the polymerizable organic solid, pTS diacetylene have been measured between 115 and 330 K in the directions parallel and perpendicular to the direction of polymer chain growth. The upper phase transition in monomer, polymer and mixed crystals at various stages of the solid-state polymerization manifests itself as a maximum in the temperature dependence of ε measured in the direction parallel to the molecular stacks, being particularly well pronounced in fully polymerized crystals. The transition was identified as an antiferroelectric one, the sublattice polarization being most probably the order parameter. The lower phase transition could be observed only in monomer and monomer-rich crystals as a shoulder on the ε(T) dependence. This transition could be detected only in the crystals containing less than ≈ 10–15% of polymer. The dielectric permittivity was found to be independent of frequency up to 3 GHz. The polymerization results in changes of the dielectric permittivity. In samples where the direction of measurements coincides with the b axis, these changes follow the monomer-polymer conversion curve. |
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