The effect of severalkey factors on the mechanical properties of multilayer polymer filmsundertensile and sheardeformations was thoroughly investigated using atomistic molecular dynamics simulations. These factors included the composition of the layers, the compatibility of polymers in the layers, the crystallinity of polymers, and the thickness of the layers, especially when it decreases to values close to the radius of gyration (Rg) of the polymers. Three types of multilayer systems were considered: polylactide/poly(3-hydroxybutyrate) (PLA/PHB) based on polymers compatible for the selected chain lengths, polylactide/polyethylene (PLA/PE) with incompatible polymers in layers, and polylactide/polylactide (PLA/PLA). It was shown that reducing thelayerthickness to the value close to Rg led to an increase in Young’s modulus for both types of systems with compatible polymers in layers PLA/PHB and with incompatiblepolymers PLA/PE. This effect was found for the systems composed of amorphous polymers. The influence of the layer thickness on shear modulus, yield stress under tensile and shear deformations was also analyzed. Young’s modulus and yield stress under tensile deformation were in line with the “rule of mixture” for all types of the systems. Both the shear modulus and yield stress under shear for PLA/PE tended to the values for bulk PE. Analysis of local atomic shear strain was employed to quantify local plastic deformations at the atomic level during the shear deformation. The pattern of local atomic shear strain distribution for the PLA/PHB and PLA/PLA systems was found to be significantly different from that for PLA/PE.

Coextruded multilayer polymer films are promising packaging materials since their architecture and properties can be adjusted while the production technology is environmentally friendly. Here, the effect of layers thickness and polymers compatibility in alternating layers on the structure and thermophysical properties of such films was studied by means of molecular dynamics simulations. The results show that the model films with layers of incompatible polymers polylactide (PLA) and polyethylene (PE) are stable in time and have very low interfacial diffusion depth even when the layers thickness is about several nanometers. Systems with incompatible polymers differ from the systems with compatible ones by the presence of anisotropy in the mobility of polymer atoms. These films also have two glass transition temperatures. Multilayer films based on compatible for the selected chain lengths polymers PLA and poly(3-hydroxybutyrate) (PHB) as well as one-component systems with PLA layers have a single glass transition point. In these films interfacial diffusion depth tends to gradually increase during the simulation. However, even for one-component system with layers thickness of 7.5 nm sufficiently stable structure of the film is formed, while heterogeneous films with PLA and PHB layers reach metastable state during the modeling with almost constant interfacial diffusion depth.

Deep eutectic solvents (DESs) are one of the most rapidly evolving types of solvents, appearing in a broad range of applications, such as nanotechnology, electrochemistry, biomass transformation, pharmaceuticals, membrane technology, biocomposite development, modern 3D-printing, and many others. The range of their applicability continues to expand, which demands the development of new DESs with improved properties. To do so requires an understanding of the fundamental relationship between the structure and properties of DESs. Computer simulation and machine learning techniques provide a fruitful approach as they can predict and reveal physical mechanisms and readily be linked to experiments. This review is devoted to the computational research of DESs and describes technical features of DES simulations and the corresponding perspectives on various DES applications. The aim is to demonstrate the current frontiers of computational research of DESs and discuss future perspectives.

We studied the structure of brushes consisting of branched oligolactide (OLA) chains grafted onto the surface of cellulose nanoparticles (CNPs) in polylactide (PLA) and compared the outcomes to the case of grafting linear OLA chains using atomistic molecular dynamics simulations. The systems were considered in a melt state. The branched model OLA chains comprised one branching point and three branches, while the linear OLA chains examined had a molecular weight similar to the branched chains. It was shown that free branches of the branched OLA chains tend to fold back toward the CNPs due to dipole-dipole interactions within the grafted layer, in contrast to the well-established behavior of the grafted uncharged branched chains. This result, however, is in qualitative agreement with the conformational behavior known for linear OLA chains. At the same time, no significant difference in the effectiveness of covering the filler surface with grafted branched or linear OLA chains was found. In terms of the expelling ability of the grafted chains and the interaction between PLA and CNP or OLA, the linear chains were broadly similar (sparse grafting) or better (intermediate or dense grafting) compared to the branched ones. Thus, the grafted lactide chains with a linear architecture, rather than their branched counterpart, may be preferable for the covalent modification of cellulose nanoparticles.

The structure of a grafted layer of lactide chains in the "dry brush" regime immersed in a melt of chemically similar polymer was examined while varying graft lengths. To this end, microsecond atomistic molecular dynamics simulations were performed. Almost no influence of graft length on the fraction of the grafted chains backfolded to the grafting surface was found. However, a structural ordering was unexpectedly observed in the system when the length of the grafted lactide chains was close to approximately 10 Kuhn segments. This ordering of the grafts is characterized by the formation of helical fragments whose structure is in good agreement with the experimental data for the α crystal of the lactide chains. Both the backfolding and the structural ordering may be viewed as the initial stage of the crystallization of the layer of grafted lactide chains. In contrast to the known behavior for conventional polymer brushes in the "dry brush" regime, the structure of the grafted lactide chains can be either amorphous or ordered, depending on the graft length N and the grafting density σ when their product Nσ is fixed.