Smart Surfaces with pH-Responsiveness Enhanced by Multiscale Hierarchical Structures Fabricated by Laser Direct Writing

In contemporary applications, smart surfaces capable of altering their properties in response to external stimuli have garnered significant attention. Nonetheless, the efficient creation of smart surfaces exhibiting robust and rapid responsiveness and meticulous controllability on a large scale remains a challenge. This paper introduces an innovative approach to fabricate smart surfaces with strong pH-responsiveness, combining femtosecond laser direct writing (LDW) processing technology with stimulus-responsive polymer grafting. The proposed model involves the grafting of poly(2-diethylaminoethyl methacrylate) (PDEAEMA) onto rough and patterned Au/polystyrene (PS) bilayer surfaces through Au-SH bonding. The incorporation of LDW processing technology extends the choice of microstructures and roughness achievable on material surfaces, while PDEAEMA imparts pH responsiveness. Our findings revealed that the difference in contact angle between acidic and basic droplets on the rough PDEAEMA-g-Au surface (∼118°) greatly surpasses that on the flat PDEAEMA-g-Au surface (∼72°). Next, by leveraging the precision control over surface microstructures enabled by the LDW processing technique, this difference was further augmented to ∼127° on the optimized patterned PDEAEMA-g-Au surface. Further, we created two distinct combined smart surfaces with varying wettability profiles on which the hydrophilic-hydrophobic boundaries exhibit reliable asymmetric wettability for acidic and basic droplets. Additionally, we prepared a separator, realizing a better visual distinction between acid and base and collecting them separately. Given the effective abilities found in this study, we postulate that our smart surfaces hold substantial potential across diverse applications, encompassing microfluidic devices, intelligent sensors, and biomedicine.

Synthesis of CO2-responsive gradient copolymers by switchable RAFT polymerization and their controlled self-assembly

Switchable RAFT agents, so-called because they can be reversibly switched by an acid/base stimulus to offer very good control over polymerization of both MAMs and LAMs, provide a route to prepare well-defined polyMAM-block-polyLAM copolymers.

Pickering Interfacial Catalysts with CO2 and Magnetic Dual Response for Fast Recovering in Biphasic Reaction

Pickering interfacial catalysis provides an excellent platform for biphasic reactions, but the separation and recycling of nanocatalysts is a challenge because of high adsorption energy of nanocatalysts at the liquid-liquid interface. In this work, we represent a new type of versatile Pickering emulsion based on magnetic and CO₂-responsive nanohybrids Fe₃O₄@SiO₂@P(TMA-DEA). The smart nanoparticles can stabilize the water-in-oil Pickering emulsion in the biphasic system and achieve the subsequent demulsification by bubbling CO₂ ascribed to their reversible switching surface. In the absence of energy barrier, the nanohybrids can be easily captured in situ by magnetic field in 2 min and showed excellent recyclability. In the Anelli system for alcohol oxidation, the nanocatalyst exhibited threefold enhancement in catalytic efficiency in comparison with an unemulsified two-phase and little loss on activity after five cycles. The conceptually novel dual-responsive system offers a green and energy-saving strategy for effective recycling of the nanocatalyst and intensification of biphasic reaction.

CO2-switchable polymer-hybrid silver nanoparticles and their gas-tunable catalytic activity

A new type CO₂-switchable AgNPs hybrids show switchable and monotonous tunable catalytic activity for the reduction of 4-nitrophenol by varying the flow rate of CO₂purged into the reaction system.