Electro-optic Properties of Siloxane Based Liquid Crystal Polymers

Khalid Al-Ammar, Bahaa Saleh, Ali Ridha, Khalid Al-Ammar Bahaa, H Saleh, Ali Ridha
2011 JOURNAL OF KUFA-PHYSICS   unpublished
A series of siloxane based side chain liquid crystal polymers have been prepared with a systematic variation in spacer length. All the polymer exhibited a smectic phase, for which the smectic-isotropic transition temperature increased as the spacer length increased. Infrared dichroism and x-ray scattering procedures have been utilized to determine the orientational order parameters for this series of polymers and these are related to the measured electrooptical properties. It is found that with
more » ... increasing spacer length (n) of polymer the threshold voltage is lowered with a functional from of n-2 and that the variation of the threshold voltage arises from changes to the intrinsic curvature elasticity rather than to differences in orientational order. A simple model is used to indicate the origion of the effects observed which appear to arise from the constraints offered by the coupling of the mesogenic units to the polymer backbone. ‫ﺍ‬ ‫ﻟﺨﻼﺻﺔ‬ ‫ﺍﻝ‬ ‫ﻣﻦ‬ ‫ﺳﻠﺴﺔ‬ ‫ﺗﺤﻀﻴﺮ‬ ‫ﺗﻢ‬ ‫ﺑﻮﻝ‬ ‫ﺗﺦ‬ ‫ﺍﻟﺴﺎﻳﻠﻮﻛﺴﺎﻧﻴﺔ‬ ‫ﻳﻤﺮﺍﺕ‬ ‫ﺕ‬ ‫ﺏ‬ ‫ﻋﻦ‬ ‫ﻟﻒ‬ ‫ﻉ‬ ‫ﺃﻅﻬﺮﺕ‬ ‫ﺍﻟﺒﻮﻟﻴﻤﺮﺍﺕ‬ ‫ﻫﺬﻩ‬ ‫ﻛﺎﻓﺔ‬ ، ‫ﺍﻟﻔﺎﺻﻞ‬ ‫ﻁﻮﻝ‬ ‫ﺑﺘﻐﻴﺮ‬ ‫ﺍﻟﺒﻌﺾ‬ ‫ﺿﻬﺎ‬ ‫ﻭ‬ ‫ﺍﻟﺴﻤﻜﺘﻲ‬ ‫ﺍﻟﻄﻮﺭ‬ ‫ﺃﻥ‬ ‫ﺍﻟﺴﻤﻜﺘﻲ‬ ‫ﺍﻟﻄﻮﺭ‬ ‫ﺣﺮﺍﺭﺓ‬ ‫ﺩﺭﺟﺔ‬ ‫ﺇﻟﻰ‬ ‫ﺍﻟﺘﻠﻮﻧﻴﺔ‬ ‫ﻁﺮﻳﻘﺔ‬ ‫ﺍﺳﺘﺨﺪﺍﻡ‬ ‫ﺗﻢ‬ .‫ﺍﻟﻔﺎﺻﻞ‬ ‫ﻁﻮﻝ‬ ‫ﺯﻳﺎﺩﺓ‬ ‫ﻣﻊ‬ ‫ﺗﺰﺩﺍﺩ‬ ‫ﺍﻻﻳﺰﻭﺗﺮﻭﺑﻲ‬ ‫ﺗﺸﺘﺖ‬ ‫ﻭ‬ ‫ﺍﻟﺤﻤﺮﺍء‬ ‫ﺗﺤﺖ‬ ‫ﻻﺷﻌﺔ‬ ‫ﺍﻷﺷﻌﺔ‬ ‫ﻋﺎﻣﻞ‬ ‫ﻻﺃﻳﺠﺎﺩ‬ ‫ﺍﻟﺴﻴﻨﻴﺔ‬ ‫ﺍﻻﺗﺠﺎﻫﻴﺔ‬ ‫ﺑﺎﻟﺨﺼﺎﺋﺺ‬ ‫ﻋﻼﻗﺘﻬﺎ‬ ‫ﺗﻮﺿﻴﺢ‬ ‫ﻭﺗﻢ‬ ‫ﻟﻠﺒﻮﻟﻴﻤﺮﺍﺕ‬ ‫ﺍﻟﻔﺎﺻﻞ‬ ‫ﻁﻮﻝ‬ ‫ﺑﺰﻳﺎﺩﺓ‬ ‫ﺍﻧﻪ‬ ‫ﻭﺟﺪ‬. ‫ﺍﻟﻤﻘﺎﺳﺔ‬ ‫ﺍﻟﻜﻬﺮﻭﺑﺼﺮﻳﺔ‬ (n) ‫ﺑﺪﻻﻟﺔ‬ ‫ﻭ‬ ‫ﺍﻟﻌﺘﺒﺔ‬ ‫ﻓﻮﻟﺘﻴﺔ‬ ‫ﺧﻔﺾ‬ ‫ﺍﻟﻰ‬ ‫ﻳﺆﺩﻱ‬ ‫ﻟﻠﺒﻮﻟﻴﻤﺮ‬ (n-2) ‫ﺍﻟﺘﻐﻴﺮ‬ ‫ﺍﻥ‬ ‫ﻭ‬ ‫ﻣﻮﺩﻳﻞ‬ ‫ﺍﺳﺘﺨﺪﺍﻡ‬ ‫ﺗﻢ‬ .‫ﺍﻻﺗﺠﺎﻫﻴﺔ‬ ‫ﻋﺎﻣﻞ‬ ‫ﺍﺧﺘﻼﻑ‬ ‫ﻛﺬﻟﻚ‬ ‫ﻭ‬ ‫ﺍﻟﻤﻄﺎﻁﻴﺔ‬ ‫ﻣﻌﺎﻣﻞ‬ ‫ﻓﻲ‬ ‫ﺍﻟﺤﺎﺻﻞ‬ ‫ﺍﻟﺘﻐﻴﺮ‬ ‫ﺇﻟﻰ‬ ‫ﻳﺆﺩﻱ‬ ‫ﺍﻟﻌﺘﺒﺔ‬ ‫ﺑﻔﻮﻟﺘﻴﺔ‬ ‫ﺍﻟﺤﺎﺻﻞ‬ .‫ﺍﻟﻔﺎﺻﻞ‬ ‫ﺑﻮﺍﺳﻄﺔ‬ ‫ﺍﻟﻔﻘﺮﻱ‬ ‫ﻋﻤﻮﺩﻩ‬ ‫ﺇﻟﻰ‬ ‫ﻟﻠﺒﻮﻟﻴﻤﺮ‬ ‫ﺍﻟﻨﻬﺎﺋﻴﺔ‬ ‫ﺍﻟﻤﺠﻤﻮﻋﺔ‬ ‫ﺑﻴﻦ‬ ‫ﺍﻟﺮﺑﻂ‬ ‫ﻗﻮﺓ‬ ‫ﺑﺴﺒﺐ‬ ‫ﺗﻨﺸﺄ‬ ‫ﺍﻟﺘﻲ‬ ‫ﻭ‬ ‫ﺍﻟﻈﻮﺍﻫﺮ‬ ‫ﻫﺬﻩ‬ ‫ﺃﺻﻞ‬ ‫ﻟﻴﻮﺿﺢ‬