Polymer-Dispersed Liquid Crystals

We have demonstrated that polarization-dependent NSOM[21] and multiphoton excited fluorescence microscopy(MPEFM)[33] methods (the latter in the far field) provide valuable new insights on the organization of nematic liquid crystals confined to micrometer and sub-micrometer sized droplets dispersed in polymer films. These materials have real commercial applications as electrically-switchable privacy windows. The NSOM and MPEFM methods show that LC droplets frequently assume interesting, unexpected shapes (for example toroids)[21,33] that distort the LC configuration, dramatically altering their optical properties and the dynamics induced by applied electric fields. We were one of the first groups to use the aluminum coating on the NSOM probe to apply concentrated electric fields to samples as a means to induce dynamics. We used this method to spatially and temporally resolve the field-induced LC dynamics in native[22,24,26,29] and ion-doped PDLC droplets.[28] The results were confirmed in model PDLC devices using MPEFM.[45,48] We demonstrated that ordered PDLC droplet arrays could be prepared in polymer inverse opals and we used MPEFM to demonstrate that unexpected long range correlations in the LC organization occurred in these materials.[35] Finally, in a series of studies using our field-modulated NSOM methods, we showed we could detect and characterize the local dynamics of PDLC droplets in the presence of photogenerated charges, as are relevant to LC-based photorefractive materials.[44,46,49,51]

Reference numbers refer to articles in the Higgins Group publication list