• Northcroft, Heidi
• Winklemann, Adam
• Lindsey, Christopher
• Londergan, Timothy
• Lee, Michael
• Zhang, Cheng
• Steier, William H.
• Dalton, Larry R.

Abstract

The roles played by spatially anisotropic intermolecular electrostatic interactions, chromophore shape, host dielectric constant, and poling field strength in defining maximum achievable electro-optic activity for electrically poled chromophore/polymer materials are investigated by equilibrium and Monte-Carlo quantum statistical mechanical calculations. Even simple Hamiltonians reproduce critical qualitative features such as the existence of a maximum in plots of electro-optic activity versus chromophore number density in a polymer matrix. Comparison of theoretical results for various methods provides a useful check on the validity of approximations employed with individual methods. The most significant conclusion to derive from a comparison of experimental and theoretical results is the dependence of maximum achievable electro-optic activity upon chromophore shape. Theoretical calculations suggest a new paradigm for the design of optimum electro-optic chromophores; realization of the desired shapes may be facilitated by dendritic synthetic approaches. In the presence of intermolecular electrostatic interactions, the dependence of electro-optic activity upon material dielectric permittivity and electric poling field strength is more complex than in the absence of such interactions. Of particularly, interest are conditions that lead to second order phase transitions to lattices containing centrically (antiferroelectrically) ordered chromophore domains. Such phase transitions can lead to further complications in the attempted preparation of device quality materials but can be effectively avoided by utilization of theoretically derived phase diagrams.

Topics

• density
• impedance spectroscopy
• polymer
• phase
• dielectric constant
• laser emission spectroscopy
• strength
• anisotropic
• phase transition
• phase diagram