Rheological Properties Study of Polymer Dispersed Liquid Crystals Doped by SiO₂ Nanoparticles

Abstract

The present report discusses the development of a novel nano-composite using a polymer dispersed liquid crystal (PDLC) and inorganic silicon dioxide (SiO₂) nanoparticles. The aim of this work was to investigate the effect of the SiO₂ nanoparticles on the rheological properties of the PDLC films. In our research described in this paper SiO₂ nanoparticle-doped polymer dispersed liquid crystal films were made from a mixture of ethylene glycol phenyl ether methacrylate (EGPEMA) pre-polymer, 4-Cyano-4′-pentylbiphenyl (5CB) liquid crystals (LC) and SiO₂ nanoparticles by the polymerization induced phase separation (PIPS) process. Doping the PDLC systems with SiO₂ improved the rheological properties of these materials; the percolation (network formation) observed reflected the good interfacial adhesion between the nanoparticles, the polymer matrix and the LC. On the other hand, a decrease in the storage modulus (G′) and loss modulus (G″) of the PDLC systems after addition of the SiO₂ nanoparticles confirmed their high flexibility and low crystallinity. A slight increase in G′ at 0.05 wt.% SiO₂ resulted in the good mechanical strength of the doped PDLC. The viscoelastic behavior of the doped and undoped PDLC systems was confirmed at high frequencies. Thermal characterization by differential scanning calorimetry (DSC) showed a decrease in the glass transition temperature (T_g) of the PDLC with 0.05 wt.% of SiO₂ nanoparticles, which showed that we had a more flexible material.

Keywords:

• 4-Cyano-4′-pentylbiphenyl (5CB) liquid crystals
• polymer dispersed liquid crystal (PDLC)
• poly ethylene glycol phenyl ether methacrylate (EGPEMA)
• rheological properties
• SiO₂ nanoparticles

Disclosure statement

No potential conflict of interest was reported by the author(s).