Observation of Ferroelectric Lithography on Biodegradable PLA Films

Poly(Lactic Acid): Recent Stereochemical Advances and New Materials Engineering

Poly(lactic acid) (PLA) is a representative biobased and biodegradable aliphatic polyester and a front-runner among sustainable materials. As a semicrystalline thermoplastic, PLA exhibits excellent mechanical and physical properties, attracting considerable attention in commodity and medical fields. Stereochemistry is a key factor affecting PLA's properties, and to this end, the engineering of PLA's microstructure for tailored material properties has been an active area of research over the decade. This Review first covers the basic structural variety of PLA. A perspective on the current states of stereocontrolled synthesis as well as the relationships between the structures and properties of PLA stereosequences are included, with an emphasis on record regularity and properties. At last, state-of-the-art examples of high-performance PLA-based materials within an array of applications are given, including packaging, fibers, and textiles, healthcare and electronic devices. Among various stereo-regular sequences of PLA, poly(L-lactic acid) (PLLA) is the most prominent category and has myriad unique properties and applications. In this regard, cutting-edge applications of PLLA are mainly overviewed in this review. At the same time, new materials developed based on other PLA stereosequences are highlighted, which holds the potential to a wide variety of PLA-based sustainable materials.

The H/F substitution strategy can achieve large spontaneous polarization in 1D hybrid perovskite ferroelectrics

Hybrid organic-inorganic perovskite (HOIP) ferroelectrics exhibit polarization reversibility and have a wide range of applications in the fields of smart switches, memorizers, sensors, etc. However, the inherent limitations of small spontaneous polarization (P s) and large coercive field (E c) in ferroelectrics have impeded their broader utilization in electronics and data storage. Molecular ferroelectrics, as a powerful supplement to inorganic ferroelectrics, have shown great potential in the new generation of flexible wearable electronic devices. The important research responsibility is to greatly improve progressiveness and overcome the above limitations. Here, a novel one-dimensional (1D) HOIP ferroelectric, (3-F-BTAB)PbBr3 (3-F-BTAB = 3-fluorobenzyltrimethylammonium), was successfully synthesized by employing the H/F substitution strategy to modify parent compound (BTAB)PbBr3 (BTAB = benzyltrimethylammonium), which undergoes a ferroelectric phase transition with Aizu notation 2/mF2 at 420 K. Notably, (3-F-BTAB)PbBr3 demonstrates exceptional ferroelectric properties with a large P s of 7.18 μC cm-2 and a low E c of 1.78 kV cm-1. As far as we know, (3-F-BTAB)PbBr3 features the largest P s among those reported for 1D lead-based HOIP ferroelectrics. This work enriches the 1D lead-based ferroelectric family and provides guidance for applying ferroelectrics in low-voltage polar memories.

Room-Temperature Anisotropic Actuation Driven by a Synergistic Order-Disorder and Displacive Phase Transition in a Ferroelectric Crystal

Actuating materials convert different forms of energy into mechanical responses. To satisfy various application scenarios, they are desired to have rich categories, novel functionalities, clear structure-property relationships, fast responses, and, in particular, giant and reversible shape changes. Herein, we report a phase transition-driven ferroelectric crystal, (rac-3-HOPD)PbI3 (3-HOPD = 3-hydroxypiperidine cation), showing intriguingly large and anisotropic room-temperature actuating behaviors. The crystal consists of rigid one-dimensional [PbI3] anionic chains running along the a-axis and discrete disk-like cations loosely wrapping around the chains, leaving room for anisotropic shape changes in both the b- and c-axes. The shape change is switched by a ferroelectric phase transition occurring at around room temperature (294 K), driven by the exceptionally synergistic order-disorder and displacive phase transition. The rotation of the cations exerts internal pressure on the stacking structure to trigger an exceptionally large displacement of the inorganic chains, corresponding to a crystal lattice transformation with length changes of +24.6% and -17.5% along the b- and c-axis, respectively. Single crystal-based prototype devices of circuit switches and elevators have been fabricated by exploiting the unconventional negative temperature-dependent actuating behaviors. This work provides a new model for the development of multifunctional mechanically responsive materials.