Tunable shape memory properties of highly stretchable poly(ester urea) random copolymers based on α-amino acids.

The exploration of biodegradable polymers with shape memory effects (SMEs) holds great promise in biomedical fields. Revealing the relationship between the SMEs and polymer structures not only contributes to interpreting the SME mechanisms, but also prompts the customization of materials properties for specific requirements. Herein, we developed a series of poly(ester urea) (PEU) random copolymers composed of two different diamine monomers based on L-alanine and L-valine, respectively. It was shown that the shape memory performance of the PEU copolymers strongly depended on the composition of two different diamine monomers in the PEU copolymers and other physical properties. This tunability likely arose from the change of polymer chain mobility and crystallinity, which were impacted by the choice of α-amino acids. Intriguingly, thin films of the PEU copolymers exhibited a high strain at break of 347-743% around the physiological temperature (35 °C). Moreover, the random copolymerization of two different sorts of diamine monomers has been demonstrated as a facile approach to precisely tailor the physical properties of the PEUs according to custom needs.

Recent progress on hydrogel actuators.

Hydrogels are known to be soft and wet smart materials that respond to external stimuli. Numerous hydrogel actuators have been developed that perform volume and shape changes, and reversible motions. Heterogeneity, periodicity, and integration of hydrogels with different properties are needed to realize biomimetic motions. In order to achieve specific actuations with predictable pathways, it is critical to fabricate hydrogel structures in a well-controlled manner. This review article summarizes recent progress in representative methods to fabricate hydrogel actuators by different methods, ranging from sequential synthesis, macroscopic supramolecular assembling, field-induced alignment, photolithography, ionoprinting, 3D printing, and gradient structuring. The advantages and limits of these methods are compared and analyzed. Finally, a brief perspective and conclusion are presented to point out some important issues for further studies.

Two-step deposition of Ag nanowires/Zn2SnO4 transparent conductive films for antistatic coatings.

Silver nanowire (AgNW) networks play an important role in the transparent conductive electrodes or antistatic coatings. In this work, we describe a facile two-step method to fabricate AgNWs/Zn2SnO4 composite films. Long AgNWs with a high aspect ratio were prepared through a modified polyol method, in which the organic octylamine hydrochloride rather than the commonly used inorganic chlorides was used as the shape-controlling agent. The AgNW networks were fabricated on the glass substrate, on which the Zn2SnO4 film was deposited, forming robust AgNWs/Zn2SnO4 composite films. The as-prepared composite films have strong adhesion, high thermal stability, low sheet resistance (5-15 ohm sq-1) and high light transmittance (85-80%), indicating a promising application prospect for transparent conductive electrodes and antistatic coatings.