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Eric Verploegen Materials Science & Engineering Grad
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Liquid crystalline block copolymers have attracted interest for their potential use as actuators. Recent research has focused on side chain liquid crystal siloxane polymers, which are crosslinked forming an elastomeric network. This type of actuator can produce reversible strains much greater than conventional ceramic piezoelectric actuators.
Block copolymer self assembly allows for the creation of a thermoplastic elastomer where hard blocks, with a high glass transition temperature (Tg), serve as physical crosslinks for a low Tg block. These physical crosslinks can be removed by elevating the temperature and the material can be repeatedly reshaped and remolded, unlike chemically crosslinked systems.
This work focuses on a polystyrene-b-polyvinylmethylsiloxane-b-polystyrene triblock copolymer with liquid crystals exhibiting a smectic C* phase attached to the PVMS central block. The smectic C* liquid crystals add a ferroelectric component to the system allowing for actuation to be controlled by the application of an electric field. The impact of morphological variations on the thermal, optical, and mechanical properties of this system are also being investigated in order to optimize actuator properties. Recent accomplishments include the optimization of shear conditions yielding a monodomain morphology across the thickness of a film.
Small Angle X-ray scattering (SAXS) pattern and a schematic of the observed morphology of a melt fiber drawn sample.
Polarized optical microscope image of a smectic liquid crystal displaying birefringence
