Rheology of rodlike nanoparticle suspensions in lyotropic liquid crystalline polymers

Liquid crystalline polymers are ideal to develop oriented and anisotropic materials. The incorporation of a nanoparticle may improve or add properties to a matrix. Small concentrations of particles smaller than the liquid crystal structural features do not affect the structure of the phase, or consequently, its properties. Similarly, small loadings of cylindrical particles may modify the rheological and electrical properties of a liquid crystal. Yet, unfavorable effects will be expected as the loading increases. It was expected that rod-like nanoparticles may be incorporated into a liquid crystalline polymer and oriented along the nematic director. Moreover, both components may be oriented using external fields. Therefore, solutions of cylindrical nanoparticles and liquid crystalline polymers may be useful to obtain oriented multifunctional materials.;In this research, the rod-like nanoparticle loading effect on the rheological and viscoelastic properties of both an isotropic and a liquid crystalline polymer solutions were determined. The inclusion of multiwalled carbon nanotubes and halloysite nanoclays up to 0.45 wt% does not affect the viscosity, neither the viscoelastic properties, of a liquid crystalline hydroxypropylcellulose solution. A maximum viscosity and viscoelastic moduli were obtained at 10 wt% of the halloysite. No indication of percolation neither changes on the polymer dynamics was obtained suggesting that the nanoparticle were oriented along the nematic director. A decrease of the steady-state viscosity and viscoelastic properties of isotropic polymer solutions was observed at small particle loadings. zeta - potential measurements demonstrated the formation of core (nanoparticle) -- shell (polymer) structures. POM measurements suggest that the polymer shell around the halloysite nanoclays have a preferential orientation on a macroscopic scale.;The effect of the application of an electric field on the rheological and viscoelastic properties was also determined for both a non- and electrorheological polymer solution loaded with multiwalled carbon nanotubes. It has been demonstrated that an electric field is not a feasible method to control the orientation of carbon nanotubes suspensions since it promotes the agglomeration of the nanoparticles, affecting the properties of a non-electrorheological hydroxypropylcellulose polymer solution. Yet, the application of a flow field can be used to obtain materials with oriented rod-like nanoparticles.