A comparison of the effects of dispersed hydrophobic or hydrophilic aerosil nanoparticles on the order and dynamics of the 5CB liquid crystal

Electron Paramagnetic Resonance Spectra Simulation Directly from Molecular Dynamics Trajectories of a Liquid Crystal with a Doped Paramagnetic Spin Probe

“…In this case for the magnetic axes of the probe, S Z $ À1=2S Y , as expected for a uniaxial particle in a uniaxial phase. The values of the order parameters for both LC and the main diffusional axis of the probe, S LC and S SP , respectively, as well as the values of rotational diffusion coefficients, calculated from the correlation times are in excellent agreement with those reported in the literature [9]. According to Table I strong correlation among the four order parameters is evident.…”

“…The N-I phase transition for 5CB occurs at 35:3 C. In the experimental EPR sample the director is not perfectly aligned in the N phase but characterized by an axial anisotropic distribution around the direction of magnetic field [9]. The director's distribution bandwidth of $15 0 is in agreement with the fit obtained using the traditional Brownian dynamics simulation model as implemented in EPRSSP_DYN EPR simulation program [7].…”

“…The y magnetic axis and the long diffusion axis of the probe are nearly collinear with the estimated angle between them of less then 15 [9]. In this case for the magnetic axes of the probe, S Z $ À1=2S Y , as expected for a uniaxial particle in a uniaxial phase.…”

“…The director's distribution bandwidth of $15 0 is in agreement with the fit obtained using the traditional Brownian dynamics simulation model as implemented in EPRSSP_DYN EPR simulation program [7]. Principle values of g and A tensors, namely, A xx ¼ 5:9 G, A yy ¼ 5:9 G, A zz ¼ 31:7 G and g xx ¼ 2:0088, g yy ¼ 2:0061, g zz ¼ 2:0027 for the spin probe dissolved in 5CB LC were taken from the literature [9,23]. Figure 2 shows EPR spectra predicted from MD simulations carried out at different temperatures.…”

“…EPR of spin probes has been used to test structural properties and molecular mobility of numerous complex molecular systems such as proteins and protein-protein complexes, DNA or RNA, polymers, lipids, nanostructures, monolayers at oil-water interfaces, and also liquid crystals (LC) [2][3][4][5][6][7][8][9][10].…”