Synthesis and Nonlinear Optical Characterization of Spin-Coated Films of Triblock Copolymers Containing Durham Polyacetylene

Sequential ring-opening metathesis polymerization of either norbornene or 9-methyltetracyclo-[6.2.1,1 3.6 .0 2,7 ]dodec-4-ene (MTD) and 7,8-bis(trifluoromethyl)tricyclo[4.2.2.0 2,5 ]deca-3,7,9-triene (TCDT) with Mo(CHCMe 3 )(NAr)(OCMe 3 ) 2 (Ar = 2,6-diisopropylphenyl) followed by linking termination with a conjugated dialdehyde results in highly soluble A-B-A triblock copolymers containing a precursor to Durham polyacetylene as the central block. A series of copolymers that contained from 10 to 200 equiv of TCDT was synthesized. The precursor copolymers were spin coated to give submicron thin films. In the case of the copolymers made with norbornene, higher spin speeds resulted in a red shift of the UV/vis spectra of the final polyacetylene-containing copolymer, indicative of longer average conjugation lengths within the film. A red shift was also observed in the UV/vis spectra of copolymers made with more equivalents of TCDT. The nonlinear optical susceptibility (X (3) ) of the copolymers was probed with third harmonic generation and degenerate four-wave mixing. X (3) increased with increasing equivalents ofTCDT. In all cases, the copolymers made with norbornene had larger X (3) values than the copolymers made with MTD.