We studied the symmetry and spatial uniformity of the orientational order of the biaxial nematic phase in the light of recent experimental observations of phase biaxiality in thermotropic bent-core and calamitic-tetramer nematics. Evidence is presented supporting monoclinic symmetry, instead of the usually assumed orthorhombic symmetry. The use of deuterium nuclear magnetic resonance to differentiate between the possible symmetries is described. The spatial aspects of biaxial order are presented in the context of the cluster model, wherein macroscopic biaxiality can result from the field-induced alignment of biaxial and possibly polar domains. The implications of different symmetries on the alignment of biaxial nematics and on the measurements of biaxial order are discussed in conjunction with the microdomain structure of the biaxial phase.

The possible symmetries of the biaxial nematic phase are examined against the implications of the presently available experimental results. Contrary to the widespread notion that biaxial nematics have orthorhombic symmetry, our study shows that a monoclinic (C2h) symmetry is more likely to be the case for the recently observed phase biaxiality in thermotropic bent-core and calamitic-tetrapode nematic systems. The methodology for differentiating between the possible symmetries of the biaxial nematic phase by NMR and by IR spectroscopy measurements is presented in detail. The manifestations of the different symmetries on the alignment of the biaxial phase are identified and their implications on the measurement and quantification of biaxiality as well as on the potential use of biaxial nematic liquid crystals in electro-optic applications are discussed.

A liquid-crystalline octapode, formed by laterally connecting calamitic mesogens to an inorganic silsesquioxane cube through flexible siloxane spacers, is studied using polarized light microscopy, differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The studies are extended to mixtures of the octapode with the respective monomer mesogens. The monomer and the octapode show a nematic phase. At lower temperatures, the octapode exhibits additionally a columnar hexagonal phase (p6mm lattice), which, on further cooling, undergoes a transition to a columnar rectangular phase (p2gg lattice). A similar phase-transition sequence is observed for mixtures of the octapode with moderate concentrations of the monomer. The columnar–columnar transition is discussed combining XRD and DSC results, and a possible model of the molecular self-organization is presented.

The impact of titanium dioxide (TiO₂) on the physical properties of poly(lactic acid) (PLA) is explored, along with the combined effect of Atomic Layer Deposition of zinc oxide (ZnO) on the nanocomposite films' surface. PLA/TiO₂ bionanocomposites are prepared via melt‐extrusion and characterized in terms of their morphological, thermal, and mechanical properties. Homogeneous dispersion of the filler offers enhanced mechanical performance for samples up to 5 wt% in TiO₂ content. Thermal stability of PLA is also slightly improved upon increasing TiO₂ content. This work also demonstrates that surface modification of PLA/TiO₂ films employing Atomic Layer Deposition of zinc oxide enhances hydrophobicity, while antimicrobial activity, although mild, appears enhanced for coated samples. Water vapor permeability is retained in both coated and uncoated nanocomposites. Surface characterization of the studied specimens, by x‐ray photoelectron spectroscopy and scanning electron microscopy, reveals subsurface diffusion and reaction of the depositing compounds within PLA, leading to a different surface chemistry involving Zn(OH)₂. This study gives valuable insights on the parameters affecting the atomic layer deposition of inorganic coatings on a polymeric substrate in the presence of nanoinclusions and, therefore, on the physical properties of the coated films, providing the pathway for their exploitation in food packaging applications.