The Studies On Synthesis And Properties Of Lyotropic Liquid Crystalline Crown Ethers

A typical lyotropic liquid crystal can be prepared by mixing water and one or more amphiphilic compounds. An amphiphilic compound has a polar head which dissolves in water(hydrophilic) and a water insoluble organic tail. Lyotropic Iquid crystals are responsive to concentration changes and to changes in temperature. Phase changes can come about by change in either concentration or temperature,or by a change of both simultaneously. The common mesophases exhibit lamellar,cubic,and hexagonal molecular packings. Amphiphilic molecules associate in such a pattern that there is a minimum of free energy and the molecular aggregates in both the dry and wet forms are not fundamentally different. In the packing of amphiphilic molecules ,like units of the molecules interact with each other,i.e.,the polar units associate with each other;likewise,nonpolar unites associate to form hydrocarbon layers in the lamellar packing. The forces directing these molecular packings are van der Waals forces and hydrophobic interactions in the hydrocarbon part of the molecule. Electrostatic forces dominate in the polar portion of the molecule.We have synthesized two novel crown ether compounds which possess the properties of lyotropic liquid crystals. The one is n-octoxymethyl-15-crown-5,the other is (15-crown-5)methyl stearate. The hydrolysis of PNPP (p- nitrophenyl pipolinate) catalysis by n-octoxymethyl-15-crown-5 micellar solution has been studied spectrephoto -meterically. The experimental results have been dealt by the kinetic model,the relative kinetic and thermodynamic parameters of hydrolytic reaction of PNPP have been obtained.