Effect of Ester Moiety on Structural Properties of Binary Mixed Monolayers of Alpha-Tocopherol Derivatives with DPPC.

Phospholipid membranes are ubiquitous components of cells involved in physiological processes; thus, knowledge regarding their interactions with other molecules, including tocopherol ester derivatives, is of great importance. The surface pressure-area isotherms of pure α-tocopherol (Toc) and its derivatives (oxalate (OT), malonate (MT), succinate (ST), and carbo analog (CT)) were studied in Langmuir monolayers in order to evaluate phase formation, compressibility, packing, and ordering. The isotherms and compressibility results indicate that, under pressure, the ester derivatives and CT are able to form two-dimensional liquid-condensed (LC) ordered structures with collapse pressures ranging from 27 mN/m for CT to 44 mN/m for OT. Next, the effect of length of ester moiety on the surface behavior of DPPC/Toc derivatives' binary monolayers at air-water interface was investigated. The average molecular area, elastic modulus, compressibility, and miscibility were calculated as a function of molar fraction of derivatives. Increasing the presence of Toc derivatives in DPPC monolayer induces expansion of isotherms, increased monolayer elasticity, interrupted packing, and lowered ordering in monolayer, leading to its fluidization. Decreasing collapse pressure with increasing molar ratio of derivatives indicates on the miscibility of Toc esters in DPPC monolayer. The interactions between components were analyzed using additivity rule and thermodynamic calculations of excess and total Gibbs energy of mixing. Calculated excess area and Gibbs energy indicated repulsion between components, confirming their partial mixing. In summary, the mechanism of the observed phenomena is mainly connected with interactions of ionized carboxyl groups of ester moieties with DPPC headgroup moieties where formed conformations perturb alignment of acyl chains, resulting in increasing mean area per molecule, leading to disordering and fluidization of mixed monolayer.

Functionalization of LC molecular films with nanocrystalline cellulose: A study of the self-assembly processes and molecular stability.

The bottom-up approach in designing and synthesis of materials using nanoparticles of different size-, shape- or chemical composition is an extreme challenge. However, in this way, new task-specific or general use nanocomposites can be obtained. This work presents, the investigations of the preparation procedures and molecular stability of Langmuir films based on cellulose nanocrystals (CNC) and different liquid crystals. The CNC-based nanocomposite with the 5CB, 5OCB, 5FCB, and 5PCH liquid crystals, have been obtained by the modified Langmuir technique. The investigations of the Langmuir monolayers gives an excellent model system for studying intermolecular interactions at the interface, which allows analyzing the ordering, sorption, desorption, association and phase separation phenomena determining physical and chemical properties of studied systems. The process of self-assembly and molecular organization on the air-liquid interphase was studied for different compositions of LC/CNC films. The compressibility profiles and the mean molecular area have been calculated. The stability of prepared monolayers has been studied to investigate the sorption and desorption processes. The morphology of the prepared systems was determined by Brewster Angle Microscopy (BAM), and the influence of the CNC on LC organization in molecular monolayers on the air-liquid interphase has been studied.