Liquid crystalline droplets in aqueous environments: electrostatic effects

Abstract

A spontaneous bipolar-to-radial structural transition within nematic microdroplets is found with systematical changes of electrostatic properties of both liquid crystal mixtures and aqueous environments.

Electric Double Layer and Orientational Ordering of Water Dipoles in Narrow Channels within a Modified Langevin Poisson-Boltzmann Model

“…A commonly oversimplified assumption when theoretically describing the EDL is the assumption of a surface charge density-independent relative permittivity in the inner (Stern) layer. Due to orientational ordering of water dipoles, the relative permittivity of the Stern layer depends on the electric field strength, that is, on the surface charge density ( ) of the electrode [ 51 , 79 , 80 , 81 , 82 ]. Furthermore, fitting the model curves with a range of free parameters to the experimental points [ 83 ] cannot prove that the Stern layer capacitance and permittivity is -independent.…”

“…A further generalization of the modified LPB model with steric effects taken into account within a lattice-statistics model of a modified LPB is found in References [ 44 , 51 , 82 ]. By taking into account asymmetric finite size of ions the modified LPB equation was generalized to (modified Langevin Eigen-Wicke model) [ 44 , 51 , 82 ]: where is the spatial dependence of relative permittivity: and Here, the parameters and are the number of lattice sites occupied by a single positive and negative hydrated ion, respectively, where a single water molecule is assumed to occupy just one lattice site. The reduced number density of lattice sites is equal to the concentration of pure water [ 44 , 51 , 82 ].…”

“…The total polarization is the sum of electronic polarization, , and orientational polarization due to the permanent water dipoles P , so that . The electronic polarization determines the refractive index of water [ 51 , 61 ] and can be expressed as To find the expression for P we must take into account the constant number density of water and the statistical-average orientation of water molecules in the solution [ 7 ]: Here, is the angle between and the cavity field acting on it (see Figure 3 ). Statistical averaging is labeled by .…”

“…In recent decades, EDL has been the subject of numerous analytical and numerical studies from Monte-Carlo methods, DFT theories and lattice models [ 3 , 7 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 ]. Additionally, interest in nanostructured materials [ 45 , 46 , 47 , 48 ] requires that theoretical models of EDL are revisited [ 49 , 50 , 51 ], also by taking into account the possible quantum effects [ 52 , 53 ].…”

Mechanical and Electrical Interaction of Biological Membranes with Nanoparticles and Nanostructured Surfaces

“…Their work was further improved by numerous theoretical studies and simulations taking into account the asymmetry of the size of the ions, direct interactions between ions, orientational ordering of water dipoles, discrete charge distribution of the surface, quantum mechanical approach, etc. [ 1 , 72 , 73 , 74 , 76 , 84 , 85 , 86 , 88 , 90 , 93 , 94 , 95 , 96 , 97 , 98 , 99 , 100 , 101 , 102 , 103 , 104 , 105 , 106 , 107 , 108 , 109 , 110 , 111 , 112 , 113 , 114 , 115 ]. The physical properties of the EDL are crucial in understanding the interaction between charged surfaces in electrolyte solutions [ 34 , 38 , 43 , 116 , 117 , 118 , 119 , 120 , 121 , 122 , 123 , 124 ].…”