Yuji Higuchi

Polymerizable zwitterionic monomers derived from amino acids exhibited ice recrystallization inhibition activity; however, this activity was lost upon polymerization into polymers.

For randomly crosslinked elastomers, coarse-grained MD shows that strength is set by network topology (cycle rank), whereas toughness depends on effective chain ratio and strand-length uniformity, providing a rational design strategy for elastomers.

The effect of adding charged lipids on the hydration water dynamics near lipid membranes was investigated using quasi-elastic neutron scattering (QENS) experiments and molecular dynamics (MD) simulations. This study focused on the zwitterionic lipid 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) mixed with the anionic lipid 1,2-dimyristoyl-sn-glycero-3-phospho-l-serine (DMPS). QENS profiles were analyzed based on four different types of hydration water dynamics. Three slower modes were identified as tightly bound, loosely bound, and free water, as previously reported, while the fastest mode was attributed to the rotational motion of the water molecules. The diffusion coefficients of the three types of hydration water increased with the addition of charged lipids, and the rotational motion of water molecules was also accelerated. The numbers of loosely and tightly bound water molecules changed slightly, whereas free water remained largely unchanged. These findings suggest that the charged headgroups of the DMPS disrupted the hydrogen-bonding network among water molecules, as supported by MD results.

Unraveling the deformation processes of semicrystalline polymers is essential for improving their durability. Owing to their hierarchical structures composed of lamellae and spherulites, many aspects of these deformation processes remain unclear at the molecular scale, such as the differences in molecular structure changes in the elastic and plastic regions and the molecular‐scale structural changes during reversible and irreversible processes. Herein, simulated creep tests of the lamellar structure of polyethylene under a constant load are performed using the coarse‐grained molecular dynamics method. Typical creep curves are observed under various constant loads. During the recovery process after stretching, the reversible and irreversible processes are distinguished by a strain of approximately 0.4 at the boundary of the elastic and plastic regions. Interestingly, during recovery, the interfaces between the amorphous and crystalline layers are highly oriented, which may inhibit strain relaxation. In terms of the molecular structure changes in the plastic region, the number of tie chains remains constant, whereas the numbers of chain ends and loops in the amorphous layers decrease. These simulation results advance current understanding of the molecular‐scale deformation processes of semicrystalline polymers, which contribute to the improvement of long‐term durability and reliability.