Atomistic and first-principles molecular dynamics simulations are employed to investigate the structure formation in a hydrated Nafion membrane and the solvation and transport of protons in the water channel of the membrane. For the water/Nafion systems containing more than 4 million atoms, it is found that the observed microphase-segregated morphology can be classified as bicontinuous: both majority (hydrophobic) and minority (hydrophilic) subphases are 3D continuous and organized in an irregular ordered pattern, which is largely similar to that known for a bicontinuous double-diamond structure. The characteristic size of the connected hydrophilic channels is about 25–50 Å, depending on the water content. A thermodynamic decomposition of the potential of mean force and the calculated spectral densities of the hindered translational motions of cations reveal that ion association observed with decreasing temperature is largely an entropic effect related to the loss of low-frequency modes. Based on the results from the atomistic simulation of the morphology of Nafion, we developed a realistic model of ion-conducting hydrophilic channel within the Nafion membrane and studied it with quantum molecular dynamics. The extensive 120 ps-long density functional theory (DFT)-based simulations of charge migration in the 1200-atom model of the nanochannel consisting of Nafion chains and water molecules allowed us to observe the bimodality of the van Hove autocorrelation function, which provides the direct evidence of the Grotthuss bond-exchange (hopping) mechanism as a significant contributor to the proton conductivity.

We present a statistical mechanical approach for predicting the self-assembled morphologies of amphiphilic copolymers—sulfonated poly (ether ether ketone) (sPEEK) and Nafion—which combine, in one macromolecule, both hydrophobic and hydrophilic segments, giving rise to a constrained hydrophobic/hydrophilic nano-separation. We have developed a coarse-grained model of sPEEK that constitutes an important class of the promising membrane materials for fuel cell applications. Using a mesoscale dynamic density functional theory (DDFT) framework, we explore the phase behavior of sPEEK and Nafion in the presence of physisorbed water. To determine the impact of polymer chemistry on the morphology of sPEEK membranes, multiblock copolymers with a variation in both molecular architecture (block size) and chemical composition (degree of sulfonation) are studied in a large window of water contents. At sufficiently high hydration levels, the simulations predict a tricontinuous morphology, where all the microphase-separated subphases—hydrophilic and hydrophobic blocks and water—percolate, resulting in the formation of three co-continuous phases. Above the percolation threshold, the distribution of water in the sPEEK membrane can be represented as a topologically complex sponge-like network consisting of narrow channels, while the main structural motif of Nafion is characterized by the presence of long but randomly packed water-filled tubes, in agreement with the fibrillar model recently proposed by Schmidt-Rohr and Chen. Although the polymer matrix of sPEEK tends to confine water to narrower channels compared to those in Nafion, the average cross-sectional area of the channels is comparable for the two systems with the same hydration level.

The main challenge of modern polymer science is to search for ways of further development of polymer civilization, which obviously includes living organisms on the Earth, without harmful consequences for civilization and the planet in its entirety. The review considers approaches to handle the problem of environmental accumulation of plastic waste. Promising trends in the development of polymer technologies, which can significantly reduce the amount of waste produced, are highlighted. Separate Sections address original methods of additive manufacturing technologies, such as the extrusion printing technique to produce multilayer films, 3D printing by using high-temperature polyimide materials, new functional siloxane oligomers and hydrogels for medical uses. Much attention is paid to the development and applications of biodegradable materials in medicine, packaging industry and agriculture. An analysis of the European strategy for plastics and plastic disposal demonstrates that it has a number of limitations due to high energy requirements and changes in Earth's carbon balance. The modern approach to plastic waste management free from these shortcomings is briefly outlined. Bibliography — 1233 references.