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Selected Works

Gregory A. DiLisi

Optics

Publication Year

Articles 1 - 3 of 3

Full-Text Articles in Physics

Viscoelastic Properties Of A Liquid-Crystalline Monomer And Its Dimer, Gregory A. Dilisi, Charles Rosenblatt, Anselm C. Griffin, Uma Hari Mar 1992

Viscoelastic Properties Of A Liquid-Crystalline Monomer And Its Dimer, Gregory A. Dilisi, Charles Rosenblatt, Anselm C. Griffin, Uma Hari

Gregory A. DiLisi

Quasielastic-light-scattering measurements are reported for a dialkoxyphenylbenzoate monomer and its dimer in their respective nematic phases. The splay and twist elastic moduli of the dimer are found to be nearly independent of molecular length. The dimer's bend modulus, however, shows an anomalous increase with decreasing temperature well below the nematic-isotropic phase transition. Monomer viscosities are consistent with typical literature values, although y, /g, pf y and gb,„d seem to be larger than expected for the dimer, where y& is the twist viscosity. The results are discussed in terms of viscoelastic properties of semiflexible rods. The elastic properties in ...


Anomaly In The Dynamic Behavior Of The Electroclinic Effect Below The Nematic—Smectic-A Phase Transition, Gregory A. Dilisi, Zili Li, Robert B. Akins, Charles Rosenblatt, Rolfe G. Petscheck Dec 1990

Anomaly In The Dynamic Behavior Of The Electroclinic Effect Below The Nematic—Smectic-A Phase Transition, Gregory A. Dilisi, Zili Li, Robert B. Akins, Charles Rosenblatt, Rolfe G. Petscheck

Gregory A. DiLisi

The electroclinic effect and dielectric response have been investigated in the British Drug House material SCE12 over its entire 15-K smectic-A range. Near the smectic-A —srnectic-C -phase transition both the electroclinic coefficient and dynamic response behave normally, the former diverging and the latter exhibiting a critical slowing down on approaching T + from above. Similar behav- A-C ior is seen in the dielectric response. Approximately 10 to 12 K above T ~, however, it was found A-C that the electroclinic relaxation time levels off and even begins to increase again on approaching the nematic —smectic-A transition from below. The magnitude of the ...


Nematic Electroclinic Effect, Gregory A. Dilisi, Zili Li, Rolfe G. Pescheck, Charles Rosenblatt Dec 1989

Nematic Electroclinic Effect, Gregory A. Dilisi, Zili Li, Rolfe G. Pescheck, Charles Rosenblatt

Gregory A. DiLisi

A tilt 0 of the principal axis of the optical dielectric tensor linear in a transverse electric field was observed for a surface-stabilized nematic liquid crystal. The electroclinic coefficient dOldE was observed to increase rapidly on approaching the nematic —smectic-A phase transition from above. This was not expected, and indicates that the incipient translational order is important to the electroclinic effect. The data are consistent with a critical exponent only over a narrow range of temperature, and in this range the apparent exponent is not that expected from theory. In addition, dielectric data are presented for this transition, and birefringence ...