PbTiO₃Nanoparticles Embedded in a Liquid Crystalline Elastomer Matrix: Structural and Ordering Properties

Abstract

Ferroelectric PbTiO3 nanoparticles were synthesized to be used as inorganic components of new composite materials based on a liquid crystalline elastomer (LCE) matrix. The preparation and characterization of the composite materials, with a relatively high concentration of PbTiO3 nanoparticles, in the form of thin films is described. The composite films retain the thermomechanical response typical of standard LCEs and the nanoparticles are distributed in the film in anisotropic structures indicating the presence of a coupling between the LCE ordered matrix and the nanomaterials. The nematoelastic coupling and the supercritical nature of the paranematic−nematic transition of the LSCE-based composites was verified also in the presence of ferroelectric nanoparticles.

Nanoparticle-Liquid Crystalline Elastomer Composites

“…The transition temperature decrease may in some cases be dependent on the concentration of nanoparticles. In the case of PbTiO 3 nanoparticles, the same authors found that the nematic transition point dropped from 74 to 72 to 71 °C for samples containing 0%, 1 wt% and 5 wt% PbTiO 2 respectively [55]. The glass transition follows a similar trend: from −4 °C to −6 °C and −7.5 °C for 0%, 1 wt% and 5 wt% samples.…”

“…Perovskite-based ferroelectric PbTiO 3 nanoparticles have also been used to form composites with LCEs [55]. The PbTiO 3 nanoparticles were synthesized by sequential precipitation of TiCl 4 and Ph(NO 3 ) followed by calcination.…”

“…However, unmodified nanoparticles easily precipitate from the reaction mixture and form a layer on the surface of the film. This was used by Domenici et al to prepare nanoparticle layers on the top of LCEs [54,55]. SWNTs were also observed to precipitate out of the reaction mixture, and to aggregate severely during centrifugation.…”

“…The use of carbon reprocessed LCEs (made by swelling the neat LCEs in solutions containing carbon nanoparticles) goes some way towards addressing this problem; since the nanoparticles are not in the inner part of the LCEs, the polymer keeps its usual LC phase and thermomechanical actuation [44]. Conducting layers formed by MoO 3−x and PbTiO 3 particles separating from the reaction mixture during centrifugation are also assumed to behave like an outer carbon layer [54,55]. However, as in the case of embedded wires [41], when the conducting layers are formed on the LCE, temperature gradients and mechanical incompatibility result in quick degradation.…”

“…For nanoparticles forming layers on the LCE surface, some groups report that there is no weakening of thermal actuation while some demonstrated an obvious weakening effect. Domenici et al used centrifugation to form the conducting layers on the surface of the LCE [54,55]. 5 wt% of PbTiO 3 nanoparticles in LCEs and 1 wt% MoO 3−x nanowires reduced the elongation from 68% of the neat LCE to 55% and 58% respectively.…”