Studies On The Solvent Effect Of The First Order Hyper-polarizabilities Of Ionic Organic Molecule And On The Dynamic Surface Tension

There are two parts in this thesis. Part I is study on the solvent effect of the first order hyper-polarizabilities of an ionic organic molecule ANS and part II is study on the dynamic surface tension.I. In the last few decades, scientists have shown great interest in the study of new nonlinear optical materials, due to their widely use and attractive application foreground, for instance, in modern laser technology, optical communication, data storage, optical information processing, and other fields. It has become an important project to find new nonlinear optical materials of high efficiency. Much emphasis has been put on organic nonlinear optical materials because they have many advantages, such as wide response wave band, good flexibility, high optical damage threshold, low cost, and easy combination and modification.The microscopic hyperpolarizabilities of organic molecules give important information on the molecular design of organic materials having macroscopic NLO susceptibilities. The hyperpolarizability of neutral molecules has usually been measured by the dc-electric field-induced second harmonic generation (EFISH) technique. In comparison with neutral molecules, ionic dyes are expected to show large hyperpolarizability because of their charged ground state. Further more, an organic ionic crystal has advantages, such as improvement of density and promotion of orientation by molecular packing, er non-ionic molecules. Thus, it is possible to obtain high-performance NLO materials from ionic organic compounds. However, there are few experimental values for the hyperpolarizabilities of ionic dyes, because the EFISH technique cannot be applied to ionic species because of the requirement to reduce the symmetry of the solution with a dc electric field. The HRS technique in solution enables one to evaluate the hyperpolarizability of ionic molecules because it has no requirement to diminish the symmetry of the solution.When molecules are solvated in the solution, the solute molecule polarize solvent molecules around it and this gives rise to a field reaction field acting back on the molecule, which will have effects on the structure of solvated molecules and their optical properties. So, in order to explain the experimental results solvent effects must be considered. New theoretical models for calculations of solvent effects must be developed.Much attention of many scientists has been shown to the Ionic Organic Molecule l-anilinonaphthalene-8-sulfonic acid ammonium (ANS) for its strong nonlinear optical response. In this thesis, the nonlinear optical properties of ANS molecule are studied. However, the theoretical results and the experimental ones do not agree very well. The geometry optimization of ANS molecule in each solvent is done by using the polarized continuum model, the nonlinear optical properties with ANS molecule in different solvents are studied. It is found that the relationship between the nonlinear optical properties and the polarities of the solvents is non-monotonic.II. Studies on surfactant systems have long been mainly concentrated on the equilibrium state. From both scientific and practical perspectives, the dynamic surface tension (DST or y (t)) is also an important property of surfactant solutions as it governs many industrial and biological processes.In this part, the Maximum Bubble Pressure Method was used to measure the dynamic surface tension yt, of cetylpyridinium bromide (CPDB) and benzyl-trimethylammonium bromide aqueous solutions, and the adsorption dynamics of two surfactants at the air-solution interface was studied.The measurement shows that diffusion-controlled mechanism exists in 1.0 ×10-4 mol/L CPDB solution, and the diffusion coefficient D of CPDB can be calculated to be 2. 09×10-10 m2 s-1, and the adsorption activation energy is taken as zero. The other three solutions with 3.0×10-4 ~9.0×10-4 mol/L CPDB concentrations are mixed diffusion-activation controlled mechanism, which can be accounted for with the extended Word-Tordai asymptotic equations Da., Ea can also be obtaine...