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.
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.of the grafts into populations of backfolded and stretched chains was most pronounced at this σ in 96 comparison with the other grafting densities [19,20]. Having fixed σ, the length of the grafted chains 97 N was varied. Six lengths of the grafted chains, N = 13, 17, 22, 30, 40 and 50, were examined. Snapshots 98 of the systems in the case of N = 13 and 50 are presented in Figure 1. Additionally, a grafted layer in 99 the "dry brush" regime with the grafting density σ = 0.88 nm −2 and the graft length N = 60 was 100 simulated. This system was compared with the one where the grafting density σ = 1.76 nm −2 and the 101 graft length N = 30 in order to examine difference in the structure between the two grafted layers at 102 a fixed product of Nσ. According to our previous estimate of the characteristic ratio [22], the Kuhn 103 segment length A for the lactide chains is equal to approximately 1.6 nm. The contour length L of the 104 grafts under consideration could be calculated as L aN , where a = 0.38 nm was the contour length 105 of the monomer in the graft. These calculations gave contour lengths L in the range 5-19 nm for the 106 considered length of the grafts at σ = 1.76 nm −2 . Thus, the number of Kuhn segments in the grafts at 107 this σ varied from approximately 3 to 12 units, lying in different orders of magnitude. For the grafts 108 where σ = 0.88 nm −2 , the contour length and the number of Kuhn segments were equal to about 23 nm 109 and 14 units, respectively. The chosen graft lengths were limited by the computational demands 110 required to perform simulations of the corresponding composites. To the best of our knowledge, the 111 considered grafts were among the longest ever studied by using atomistic molecular dynamics 112 simulations. In the present study, the total number of atoms in the system with the grafted layer at 113 σ = 1.76 nm −2 and N = 13 was about 53,000, while the composite c...
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...
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.
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