Design of new polydiacetylenes as self assembling second order nonlinear optical polymers
A series of diacetylenic monomers containing a polarizable aromatic substituent at one side and a flexible sidegroup with hydrogen bonding groups at the other side are reported. BPOD, 3-BPOD and NPOD are metallic red as polymerized and highly soluble in chloroform, phenol and trifluoroacetic acid. They undergo a dramatic color transition from red(h,-510 nm) to purple(h,-590 nm) upon the addition of a nonsolvent such as hexane. Films with excellent optical quality can be prepared by spin coating or casting the solutions of these polymers. These polydiacetylenes self assemble in an acentric stable polar organization without recourse to poling. Second harmonic signals are observed from the monomer crystals of these materials as well as the bulk polymers.