TAILIEUCHUNG - Ferroelectrics Physical Effects Part 6

Tham khảo tài liệu 'ferroelectrics physical effects part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 190 Ferroelectrics - Physical Effects composed only of compounds with fluoroalkyl group giving the induction of SmC A phase. Compound 1 was dopped with compound 13 having terphenyl rigid core lateraly substituted by four fluorine atoms Fig. 18. This examples is an exeption from the rule that induction of SmC A phase can appear in mixtures of compounds differing in the polarity. The steric factors play also crucial role in this behaviour because the induction of SmC A phase was not found in mixtures of both nonchiral compounds. For the last system it cannot be also excluded that the appearance of SmC A phase could be a result of interactions between nonfluorinated and fluorinated rigid core. 4. Conclusion There are many systems in which the induced antiferroelectric phase can be observed. Compounds with polar group 1 3-5 have virtual SmC A phase. They have similar structure to compounds forming SmC A phase by themselvs . the structure of compound 1 and 4 is similar to the structure of the first antiferroelectric compound MHPOBC they have the same rigid core and chiral terminal chain. The placement of molecules of compounds with virtual SmC A phase which have a tendency to form the antiferroelectric phase but cannot fulfil all conditions in a suitable matrix of less polar compounds causes the appearance of an antiferroelectric phase. The ability of more polar compounds with virtual SmC A phase for induction of this phase decreases in the following order compounds 1 3 4 and 5. Compounds with cyano group in terminal chain have smaller ability than compounds with fluoroalkyl group. Compounds with biphenylate core have bigger ability than compounds with benzoate core. The same is observed in group of less polar compounds with alkyl group in the terminal chain . the biphenylate core is more preferable as well as the increase of the terminal chain causes the inrease of tendency to induce SmC A phase. In systems of similar polarity nonadditive behaviuor can be .

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