Polylactide (PLA) composites containing graphene nanosheets were prepared by the approach of solution mixing for a crystallization study. The results revealed that the graphene nanosheets are well distributed in the PLA matrix, leading to an evident viscosity increase despite their dispersion as multilayered structures in stack form. Both the cold and melt crystallization behaviors of PLA were found to depend strongly on the presence of the graphene nanosheets. During cold crystallization, the graphene nanosheets merely act as an inert filler, and the increased viscosity results in a decrease of the overall crystallization rate of the composite relative to neat PLA. However, the graphene nanosheets can act as a heterogeneous nucleating agent, which is their dominant role during melt crystallization. As a result, the composite shows a higher crystallization rate than neat PLA under these conditions.

Self‐assembled membranes with periodic wrinkled patterns are the critical building blocks of various flexible electronics, where the wrinkles are usually designed and fabricated to provide distinct functionalities. These membranes are typically metallic and organic materials with good ductility that are tolerant of complex deformation. However, the preparation of oxide membranes, especially those with intricate wrinkle patterns, is challenging due to their inherently strong covalent or ionic bonding, which usually leads to material crazing and brittle fracture. Here, wrinkle‐patterned BaTiO3 (BTO)/poly(dimethylsiloxane) membranes with finely controlled parallel, zigzag, and mosaic patterns are prepared. The BTO layers show excellent flexibility and can form well‐ordered and periodic wrinkles under compressive in‐plane stress. Enhanced piezoelectricity is observed at the sites of peaks and valleys of the wrinkles where the largest strain gradient is generated. Atomistic simulations further reveal that the excellent elasticity and the correlated coupling between polarization and strain/strain gradient are strongly associated with ferroelectric domain switching and continuous dipole rotation. The out‐of‐plane polarization is primarily generated at compressive regions, while the in‐plane polarization dominates at the tensile regions. The wrinkled ferroelectric oxides with differently strained regions and correlated polarization distributions would pave a way toward novel flexible electronics.

No abstract

To overcome the fundamental challenge of the weak natural response of antiferromagnetic materials under a magnetic field, voltage manipulation of antiferromagnetic interaction is developed to realize ultrafast, high-density, and power efficient antiferromagnetic spintronics. Here, we report a low voltage modulation of Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction via ionic liquid gating in synthetic antiferromagnetic multilayers of FeCoB/Ru/FeCoB and (Pt/Co)2/Ru/(Co/Pt)2. At room temperature, the distinct voltage control of transition between antiferromagnetic and ferromagnetic ordering is realized and up to 80% of perpendicular magnetic moments manage to switch with a small-applied voltage bias of 2.5 V. We related this ionic liquid gating-induced RKKY interaction modification to the disturbance of itinerant electrons inside synthetic antiferromagnetic heterostructure and the corresponding change of its Fermi level. Voltage tuning of RKKY interaction may enable the next generation of switchable spintronics between antiferromagnetic and ferromagnetic modes with both fundamental and practical perspectives.

No abstract