Theoretical and Experimental Second Harmonic Generation Studies of the Rotational Elastic Response of a Dye Molecule in a Random Copolymer of Styrene and Methyl Methacrylate

Epoxy-Based Nonlinear Optical Polymers from Post Azo Coupling Reaction

“…[21][22][23][24][25] Moreover, the bulk NLO properties of the polymer systems also depend on the dynamic process which control the buildup and maintenance of noncentrosymmetric alignment of NLO dyes in polymer matrices. [26][27][28] Therefore, the hyperpolarizabilities of the chromophores measured in solution may not be appropriate for describing NLO properties of polymers containing these chromophores. 4 Second, the different chromophores introduced into the polymer systems will not only impart the desired NLO response, but as they are covalently bonded to the polymers, other physical properties such as thermal properties and processing features will be affected.…”

“…First, the optical nonlinearities of chromophores have often been characterized by the hyperpolarizabilities measured through two popular methods: viz., electric field induced second harmonic generation (EFISH) and hyper-Rayleigh scattering measurements. − These methods provide a well-defined platform to compare the second-order hyperpolarizabilities of the chromophores. However, it has been shown that the energy levels, the relative contributions of different resonance forms to the ground state, and the molecular geometry of the NLO chromophores will all depend on the medium in which they are embedded. − Moreover, the bulk NLO properties of the polymer systems also depend on the dynamic process which control the buildup and maintenance of noncentrosymmetric alignment of NLO dyes in polymer matrices. − Therefore, the hyperpolarizabilities of the chromophores measured in solution may not be appropriate for describing NLO properties of polymers containing these chromophores . Second, the different chromophores introduced into the polymer systems will not only impart the desired NLO response, but as they are covalently bonded to the polymers, other physical properties such as thermal properties and processing features will be affected.…”

Effects of Viscoelastic Properties on the Dielectric and Electrooptic Responses of Low-TgGuest−Host Polymers

“…Other studies − have clearly demonstrated that below T g these properties follow an Arrhenius law with an activation energy varying with the considered polymer. Kuzyk et al have developed a technique to estimate the elastic constant by SHG measurements and have compared the calculated molecular elasticity with the measured elastic modulus. , In this way, they have shown the influence of the matrix elasticity on the orientational dynamics of chromophores. Whereas the effects of mechanical memory are not very significant above T g , they are omnipresent near and below T g and play a major role in the orientational processes of chromophores .…”

Structure−Activity Relationship of New Nonlinear Optical Organic Materials Based on Push−Pull Azo Dyes. 3. Guest−Host Systems

“…The fast component could be easily fitted by either a KWW function or a simple exponential. Examples of both the former 3,6 and the latter procedure 7,16 can be found in the literature. The simple exponential fit was adopted in this case.…”

“…Many efforts have been devoted to the study of orientation and randomization phenomena in glassy guest−host systems, − generally using second harmonic generation (SHG) as a tool for monitoring the growth and the decay of the organization of dipoles. However, to the best of our knowledge, no useful correlation among the chemical structure of NLO-active chromophores and their orientability and stability of second-order NLO properties has been yet presented.…”