Programming temporal shapeshifting

Shapeshifting enables a wide range of engineering and biomedical applications, but until now transformations have required external triggers. This prerequisite limits viability in closed or inert systems and puts forward the challenge of developing materials with intrinsically encoded shape evolution. Herein we demonstrate programmable shape-memory materials that perform a sequence of encoded actuations under constant environment conditions without using an external trigger. We employ dual network hydrogels: in the first network, covalent crosslinks are introduced for elastic energy storage, and in the second one, temporary hydrogen-bonds regulate the energy release rate. Through strain-induced and time-dependent reorganization of the reversible hydrogen-bonds, this dual network allows for encoding both the rate and pathway of shape transformations on timescales from seconds to hours. This generic mechanism for programming trigger-free shapeshifting opens new ways to design autonomous actuators, drug-release systems and active implants

Submicrometer-Encapsulation of NaBH₄ by Dopamine End-Functionalized Polystyrene: Gas Generation at Oil–Water Interfaces

We present a single-step, grafting-to synthetic method for the encapsulation of particulate NaBH₄ by dopamine end-functionalized polymer chains. Metal–catechol coordination chemistry is used to produce core–shell capsules, which generate H₂ gas exclusively upon adsorption to an oil–water interface. Significantly, the synthetic process enables facile control of core diameter, shell thickness, and the chemistry of both shell and core. The interfacial reactivity of these stimuli-responsive capsules may be engineered for various applications such as medical diagnostics, therapeutics, and subsurface imaging. In addition to their triggered reactivity, the capsules react in a manner independent of pressure and are thus well-suited for high pressure subsurface environments

Well-Defined Zwitterionic Microgels: Synthesis and Application as Acid-Resistant Microreactors

This paper describes the synthesis, swelling behavior, and applications of well-defined narrowly dispersed zwitterionic (ZW) microgels prepared by dispersion polymerization in aqueous media. Microgel stability was achieved through precise control of the dispersant composition, timely addition of a cross-linker after the nucleation stage, and the utilization of ionic initiators. Dispersion polymerization allowed for incorporation of both hydrophilic and hydrophobic comonomers, including acrylamide (AAm) and dopamine methacrylamide (Dopa-MA). The broad variety of compositions created many opportunities for practical applications such as encapsulation of mineral acids and synthesis of metal nanoparticles. The swelling behavior of ZW-<i>co</i>-AAm microgels in 6 M HCl was particularly interesting: whereas ZW moieties remained stable in contact with the strong acid, the amide groups underwent hydrolysis to carboxylic acid, resulting in microgel contraction and acid release. Zw-<i>co</i>-Dopa-MA microgels were employed as particulate microreactors, where the ZW moieties played a role of an osmotic pump delivering Ag ions to the DOPA moieties for conversion to silver nanoparticles uniformly dispersed inside the microgel particles