<span style="font-size: 22.0pt;mso-bidi-font-size:15.0pt;font-family:"Times New Roman","serif"; mso-bidi-font-weight:bold">Dielectric constant/loss behaviour of 11.6 MeV/n U^{<span style="font-size:17.0pt;mso-bidi-font-size:10.0pt;font-family:"Times New Roman","serif"; mso-bidi-font-weight:bold">238</span>}<span style="font-size:17.0pt; mso-bidi-font-size:10.0pt;font-family:"Times New Roman","serif";mso-bidi-font-weight: bold"> <span style="font-size:22.0pt;mso-bidi-font-size:15.0pt; font-family:"Times New Roman","serif";mso-bidi-font-weight:bold">ion irradiated poly (<i style="mso-bidi-font-style:normal">p</i>-hydroxy benzoic acid-co-ethylene terephthalate) liquid crystal polymer </span></span></span>

Abstract

633-636<span style="font-size: 15.0pt;mso-bidi-font-size:8.0pt;font-family:" arial","sans-serif""="">Polymer liquid crystal, a copolymer or polyethylene terephthalate (PET) and poly hydroxy henzoic acid (PHB) whence referred as PET/x PHB where <span style="font-size:15.5pt;mso-bidi-font-size:8.5pt; font-family:" times="" new="" roman","serif""="">x <span style="font-size: 15.0pt;mso-bidi-font-size:8.0pt;font-family:" arial","sans-serif""="">represents the molar concentration or PHB, for x=0.3 and 0.7 or 165 µ<span style="font-size:13.0pt; mso-bidi-font-size:6.0pt;font-family:HiddenHorzOCR;mso-hansi-font-family:Arial; mso-bidi-font-family:HiddenHorzOCR">m nominal <span style="font-size: 15.0pt;mso-bidi-font-size:8.0pt;font-family:" arial","sans-serif""="">thickness were irradiated with 11.6 MeV /n <span style="font-size:19.5pt;mso-bidi-font-size: 12.5pt;font-family:" times="" new="" roman","serif""="">U238 -ion at DRAMSTADT (Germany) with fluence 1×10<span style="font-size: 13.0pt;mso-bidi-font-size:6.0pt;font-family:" times="" new="" roman","serif""="">6 ions/cm2 .<span style="font-size:15.0pt;mso-bidi-font-size:8.0pt;font-family: " arial","sans-serif""="">The dielectric constant/loss measurements for these polymer liquid crystal samples were measured in the temperature range 20-220°C b<span style="font-size:15.0pt;mso-bidi-font-size:8.0pt;font-family: " arial","sans-serif""="">y using Keithley's precision LCZ meter for frequencies 120Hz, 1 kHz, 10kHz and 100kHz. An increase in the dielectric constant at low temperature (20-60 °C) mainly ascribed to <span style="font-size:15.0pt; mso-bidi-font-size:8.0pt;font-family:" ms="" mincho";mso-bidi-font-family:arial"="">α-relaxation, which depends upon the molar concentration of PHB. This peak has been attributed to the polar nature or both PET and PHB. The α<span style="font-size:15.0pt;mso-bidi-font-size: 8.0pt;font-family:" arial","sans-serif""="">-relaxation is followed by suppression in dielectric constant or PET/0.3PHB and sharp increase in dielectric constant of -PET/0.7PHB from which one can understand that, due to irradiation, the PET rich phase has been affected drastically. The decrease in the dielectric constant <span style="font-size: 15.0pt;mso-bidi-font-size:8.0pt;font-family:" arial","sans-serif""="">at higher temperatures is due to the increase in crystallinity as annealing-like effects are also induced due to irradiation by <span style="font-size: 15.0pt;mso-bidi-font-size:8.0pt;font-family:" arial","sans-serif""="">energetic heavy ions. The peak in the dielectric loss (0.3 PHB) curve ascribed to the space charge relaxation processes, which is in accordance with the thermally-stimulated polarization current behaviour. A continuous decrease in the dielectric loss curve (0.7PHB) ascribed to the <i style="mso-bidi-font-style: normal">m-transition that is in conformity with the investigations on internal friction. </span