Regional Control of Multistimuli-Responsive Structural Color-Switching Surfaces by a Micropatterned DNA-Hydrogel Assembly

Structural colors have advantages compared with chemical pigments or dyes, such as iridescence, tunability, and unfading. Many studies have focused on developing the ability to switch ON/OFF the structural color; however, they often suffer from a simple and single stimulus, remaining structural colors, and target selectivity. Herein, we present regionally controlled multistimuli-responsive structural color switching surfaces. The key part is the utilization of a micropatterned DNA-hydrogel assembly on a single substrate. Each hydrogel network contains a unique type of stimuli-responsive DNA motifs as an additional cross-linker to exhibit swelling/deswelling via stimuli-responsive DNA interactions. The approach enables overcoming the existing limitations and selectively programming the DNA-hydrogel to a decrypted state (ON) and an encrypted state (OFF) in response to multiple stimuli. Furthermore, the transitions are reversible, providing cyclability. We envision the potential of our method for diverse applications, such as sensors or anticounterfeiting, requiring multistimuli-responsive structural color switching surfaces

Bis(β-ketoimino)nickel(II) Complexes for Random Copolymerization of Norbornene and Methyl 5‑Norbornene-2-carboxylate with Controlled Ester Group Incorporation

A series of bis­(β-ketoimino)­nickel­(II) complexes with p-substituted N-phenyl groups, Ni­[CH3C­(O)­CHC­(NPhR)­CH3]2 (Ni1: R = −OCH3; Ni2: R = −CH3; Ni3: R = −CF3), were synthesized, and their general coordination geometry was elucidated by single-crystal X-ray diffraction analysis of Ni3. These complexes were paired with tris­(pentafluorophenyl)­borane (B­(C6F5)3) to catalyze the vinyl addition copolymerization of norbornene (NB) and methyl 5-norbornene-2-carboxylate (NBE). All the catalyst systems exhibited high catalytic activities (>105 gpolymer molNi–1 h–1) at NBE feed contents of up to 50 mol %, resulting in the production of copolymers with high molecular weights (Mw = 135–355 kg mol–1, Đ = 1.78–2.12). In addition, the content of polar ester groups was precisely controlled by the feed ratio of the monomers. For Ni3, two monomer reactivity ratios were found to be close to unity (Fineman–Ross method: rNB = 0.951, rNBE = 0.903; Kelen–Tüdös method: rNB = 1.15, rNBE = 0.978). Since the copolymerization behaviors were revealed to be independent of the electronegativity of p-substituent, all the catalyst systems of Ni1–Ni3/B­(C6F5)3 were considered to serve the random copolymerization of NB and NBE. The resulting poly­(norbornene-random-methyl 5-norbornene-2-carboxylate)­s exhibited the dielectric and surface properties well tunable by compositional modulation

Palladium(II)-Catalyzed Synthesis of a Vinyl-Addition Ultrahigh-Molecular-Weight Polynorbornene Copolymer with an Entanglement Network for Enhanced Fracture Resistance

The fracture resistance of a cyclic olefin copolymer (COC) was enhanced by incorporating an entanglement network. The vinyl-addition copolymerization of norbornene (NB) and 5-octyl-2-norbornene (OctNB) was achieved using a catalyst system composed of Pd(MesNCHC6H4PPh2)Cl2 (Mes = 2,4,6-Me3C6H2), triisobutylaluminum, and triphenylmethylium tetrakis(pentafluorophenyl)borate. Despite exhibiting limited initiation efficiency, this catalyst system successfully produced vinyl-addition ultrahigh-molecular-weight poly(norbornene-random-5-octyl-2-norbornene) (VA-UHMWP(NB-r-OctNB)) with a number-average molecular weight (Mn) exceeding 103 kDa. To assess the impact of the molecular weight, four VA-P(NB-r-OctNB)s with Mn values of 292–1120 kDa were synthesized by introducing 1-hexene as a chain transfer agent during polymerization. Tensile testing of the VA-P(NB-r-OctNB) films revealed an increase in tensile toughness, accompanied by an increase in elongation at break, up to an Mn value of 680 kDa. This discovery suggests that the entanglement network plays a crucial role in enhancing the fracture resistance of this COC, ultimately contributing to decoupling its stiffness and brittleness