Electro-optic properties of chiral helix oligo-L-lactic acid

摘要

Chiral helix materials have large optical rotatory power, and therefore, their application has been caught much attention for optical elements and/or optical switching devices. Among such helical polymers, chiral poly-lactic acid can be easily synthesized without racemization. However, the film formation of poly-lactic acid for optical application is difficult because of the high crystallinity. We synthesized the chiral oligo-L-lactic acid with the definite degree of polymerization by using GPC fractionation technique and found that the optical rotatory power reached to a saturated constant value even in the octamer. Such oligomers whose repeating units are less than 14 are liquid state at ambient temperature. These results indicate that the helical structure has stably existed even in the low molecular weight oligomers. The oligo-L-lactic acid could be oriented in liquid crystalline cell and by electro-poling treatment. The orientation structure was discussed from ORD spectra and SHG measurement.