Glasses with Tunable Liquid Crystalline Order Glasses with Tunable Liquid Crystalline Order The goals of the work carried out as sub-contract to the project on "Organic Glasses with Tunable Liquid Crystalline Order" will connect to all three main components of the proposed research: (1) determining what governs the kinetic arrest of certain liquid crystalline (LC) states, (2) identifying structures of glasses with different LC order, and (3) the stability of LC glasses. Critical input to addressing these issues are the rotational dynamics of the molecules involved about their distinct axes. Dielectric relaxation techniques have proven to be very effective tools for the characterization of liquid and glassy dynamics, partly due to the wide frequency range and extraordinary sensitivity of the method. We will employ our dielectric equipment to characterize the dynamics and structural aspects of LC materials in the isotropic, nematic, smectic, liquid and glassy states. The usable sample temperature range in our lab is 20 K to 490 K, sufficient to melt samples and create rigid glasses. Samples can be quenched as fast as ~500 K per minute and then measured across a frequency range of 1 mHz to 10 MHz. For part (1), the proposed dielectric experiments will quantify the time scales of molecular motion, help identifying whether rotation proceeds around the short or long axis of the LC molecule. In some cases, the signal of interest will be buried below the stronger conductivity effects, and we will employ charge cleaning techniques as well as dedicated analyses to recover the signature of rotational dynamics. For part (2), secondary dielectric relaxation process in the glassy states will be characterized, which are known to provide information about how densely molecules are packed. For part (3), long term temperature stability and measurement automation in our lab will be used to assess the stability of various LC glasses by recording the dielectric signatures of physical aging or crystallization processes. In close collaboration with the group of Lian Yu at UW Madison, sample material selection, measurement conditions, and data analyses will be coordinated through regular Skype meetings and occasional mutual lab visits.
|Effective start/end date||8/15/19 → 7/31/22|
- National Science Foundation (NSF): $206,685.00
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