It is known that organic and polymeric materials with large delocalized .pi.-electron systems can exhibit nonlinear optical response, which in many cases is a much larger response than by inorganic substrates.
In addition, the properties of organic and polymeric materials can be varied to optimize other desirable properties, such as mechanical and thermoxidative stability and high laser damage threshold, with preservation of the electronic interactions responsible for nonlinear optical effects.
Thin films of organic or polymeric materials with large second order nonlinearities in combination with silicon-based electronic circuitry have potential as systems for laser modulation and deflection, information control in optical circuitry, and the like.
Other novel processes occurring through third order nonlinearity such as degenerate four-wave mixing, whereby real-time processing of optical fields occurs, have potential utility in such diverse fields as optical communications and integrated circuit fabrication.
Of particular importance for conjugated organic systems is the fact that the origin of the nonlinear effects is the polarization of the .pi.-electron cloud as opposed to displacement or rearrangement of nuclear coordinates found in inorganic materials.
Nonlinear optical properties of organic and polymeric materials was the subject of a symposium sponsored by the ACS division of Polymer Chemistry at the 18th meeting of the American Chemical Society, September 1982. Papers presented at the meeting are published in ACS Symposium Series 233, American Chemical Society, Washington, D.C. 1983.
The above recited publications are incorporated herein by reference.
Of more specific interest with respect to the present invention embodiments is prior art relating to polymers with comb-like side chains. Eur. Polym. J., 18, 651(1982) describes liquid crystalline polymers of the smectic and nematic types with cyanobiphenyl groups in the side chain: ##STR2## where R is hydrogen or methyl, n is an integer of 2-11, and X is an oxy, alkylene or carbonyloxy divalent radical.
A disadvantage of liquid crystalline polymers which exhibit mesogenic side chain nonlinear optical response is an observed light scattering effect when the polymer is in the form of a solid phase optical medium, e.g., the polymer medium exhibits more than about 20 percent scattering of transmitted incident light. The light scattering is due to deviations from ideal molecular order which accommodate defects that are not optically clear.
There is continuing interest in the theory and practice of polymers which are characterized by comb-like side chain structures which can be oriented in an applied external field.
There is also an increasing research effort to develop new nonlinear optical organic systems for prospective novel phenomena and devices adapted for laser frequency conversion, information control in optical circuitry, light valves and optical switches. The potential utility of organic materials with large second order and third order nonlinearities for very high frequency application contrasts with bandwidth limitations of conventional inorganic electrooptic materials.
Accordingly, it is an object of this invention to provide a novel class of bisacrylate monomers.
It is another object of this invention to provide bisacrylate polymers having side chains which exhibit nonlinear optical response.
It is a further object of this invention to provide an optically transparent medium of a thermoset bisacrylate polymer which exhibits second order nonlinear optical response.
Other objects and advantages of the present invention shall become apparent from the accompanying description and examples.