Molecular Orientation in Polymer-Dispersed Liquid Crystals Using Time-Resolved FT-IR

Abstract

Molecular orientation of nematic microdroplets in polymer-dispersed liquid crystal (PDLC) films has been investigated by time-resolved FT-IR (TR/FT-IR) in the presence of an applied electric field. Two kinds (fast and slow) of reorientation processes are found, and these may be attributed to reorientation of liquid crystal molecules at the surface and the central region of droplets. In addition, an induction time has been observed before the onset of the actual reorientation. It is suggested that there are no essential differences between rigid and flexible molecular segments with respect to reorientation dynamics of at least 1 ms time resolution. TR and micro-FT-IR techniques have been combined in order to study the reorientation dynamics of the different regions of droplets.

Time-Resolved Fourier Transform Infrared Spectroscopic Imaging

“…This behavior was also observed in the only other publication of spatially resolved dynamics. 36 That study, however, did not discuss this phenomenon, which we believe arises from molecules relaxing back to their equilibrium positions and passing through the equatorial plane. Additionally, hydrodynamic instabilities, especially at higher applied elds, may contribute to the observed absorbance overshoot.…”

Time-Resolved Fourier Transform Infrared Spectroscopic Imaging

“…This behavior was also observed in the only other publication of spatially resolved dynamics. 36 That study, however, did not discuss this phenomenon, which we believe arises from molecules relaxing back to their equilibrium positions and passing through the equatorial plane. Additionally, hydrodynamic instabilities, especially at higher applied elds, may contribute to the observed absorbance overshoot.…”

Noninvasive Imaging of Molecular Dynamics in Heterogeneous Materials

“…Hence, a spatially resolved dynamic response of PDLCs that includes information on individual molecular orientation and interactions has not been generally accessible. The average molecular dynamics of neat LCs , and a PDLC , have been examined using single detector time-resolved IR spectroscopy. As opposed to these studies of bulk liquid crystal, the LC in a PDLC resides in several different local environments and is subject to additional constraints from domain boundaries and defects.…”

Probing the Mesoscopic Chemical and Physical Properties of Polymer-Dispersed Liquid Crystals

“…As shown above, fast and slow reorientation processes are observed in the data. Reproduced from [140]. C NMR correlation data depicting the mobility of various functional groups of the liquid crystal in PDLC films containing droplets of different sizes.…”

Time-Resolved Fourier Transform Infrared Spectroscopic Imaging

“…This behavior was also observed in the only other publication of spatially resolved dynamics. 36 That study, however, did not discuss this phenomenon, which we believe arises from molecules relaxing back to their equilibrium positions and passing through the equatorial plane. Additionally, hydrodynamic instabilities, especially at higher applied elds, may contribute to the observed absorbance overshoot.…”

Noninvasive Imaging of Molecular Dynamics in Heterogeneous Materials

“…Hence, a spatially resolved dynamic response of PDLCs that includes information on individual molecular orientation and interactions has not been generally accessible. The average molecular dynamics of neat LCs , and a PDLC , have been examined using single detector time-resolved IR spectroscopy. As opposed to these studies of bulk liquid crystal, the LC in a PDLC resides in several different local environments and is subject to additional constraints from domain boundaries and defects.…”

Probing the Mesoscopic Chemical and Physical Properties of Polymer-Dispersed Liquid Crystals

“…As shown above, fast and slow reorientation processes are observed in the data. Reproduced from [140]. C NMR correlation data depicting the mobility of various functional groups of the liquid crystal in PDLC films containing droplets of different sizes.…”

Time-Resolved Fourier Transform Infrared Spectroscopic Imaging

“…This behavior was also observed in the only other publication of spatially resolved dynamics. 36 That study, however, did not discuss this phenomenon, which we believe arises from molecules relaxing back to their equilibrium positions and passing through the equatorial plane. Additionally, hydrodynamic instabilities, especially at higher applied elds, may contribute to the observed absorbance overshoot.…”

Noninvasive Imaging of Molecular Dynamics in Heterogeneous Materials

“…Hence, a spatially resolved dynamic response of PDLCs that includes information on individual molecular orientation and interactions has not been generally accessible. The average molecular dynamics of neat LCs , and a PDLC , have been examined using single detector time-resolved IR spectroscopy. As opposed to these studies of bulk liquid crystal, the LC in a PDLC resides in several different local environments and is subject to additional constraints from domain boundaries and defects.…”

Probing the Mesoscopic Chemical and Physical Properties of Polymer-Dispersed Liquid Crystals

“…As shown above, fast and slow reorientation processes are observed in the data. Reproduced from [140]. C NMR correlation data depicting the mobility of various functional groups of the liquid crystal in PDLC films containing droplets of different sizes.…”