کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1811094 | 1025581 | 2011 | 10 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Influence of moieties for the phase stability, spontaneous polarization and dielectric relaxations in an achiral ferroelectric bent liquid crystal, PBUOB
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
فیزیک و نجوم
فیزیک ماده چگال
پیش نمایش صفحه اول مقاله

چکیده انگلیسی
The occurrence of ferroelelectric phases and influence of chemical moieties in the area of supra-molecular achiral Bent core Liquid Crystals (BLCs) are reviewed. Synthesis of an intermediate/higher homolog of PBnOB series (for n=11), PBUOB, viz. 1,3âPhenyline-Bis(4âUndecylOxy Benzoate), is presented. Smectic LC phases exhibited by PBUOB are characterized by Polarized Optical Microscopy (POM), Differential Scanning Calorimetry (DSC) and Spontaneous Polarization (PS) techniques. Observations infer a bi-variant FE LC smectic phase occurrence, viz., isotropicâB2(FE)âB5(FE)âsolid phases in cooling and solidâB5âisotropic phases in heating scans. Occurrence of B2 phase is monotropic (in cooling), while B5 phase is enantiotropic. I-B2 and B2-B5 phase transitions are found to be of first order nature. The FE phases possess a moderate PS value of â¼40 nC cmâ2. Transition temperatures from dielectric studies agree with those from TM and DSC. Two modes of relaxations are observed, viz., a slow scissor mode at â¼1 kHz and a fast mode at â¼1 MHz. Anisotropic Dipolar Model is proposed to explain the reorientation mechanism. Arrhenius shifts of Relaxation Frequency (fR) show differing activation energies for two modes, i.e., 0.11 and 0.98 eV; 0.25 and 1.18 eV in B2 and B5 phases, respectively. Temperature variation of dielectric increment Îε and α-parameter LC phases reveals the relative fixture of dipole moment in polar smectic layers. An analytical study for the thermal stability, PS and fR in the FE phases is presented with respect to the constitution and configuration of moieties in BLCs.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Physica B: Condensed Matter - Volume 406, Issue 11, 15 May 2011, Pages 2081-2090
Journal: Physica B: Condensed Matter - Volume 406, Issue 11, 15 May 2011, Pages 2081-2090
نویسندگان
P.V. Chalapathi, M. Srinivasulu, V.G.K.M. Pisipati, Ch. Satyanarayana, D.M. Potukuchi,