Competitive molecular-/ion-recognition responsive characteristics of poly(N-isopropylacrylamide-co-benzo-12-crown-4-acrylamide) copolymers with benzo-12-crown-4 as both guest and host units.

Novel dual molecular- and ion-recognition responsive poly(N-isopropylacrylamide-co-benzo-12-crown-4-acrylamide) (PNB12 C4 ) linear copolymers with benzo-12-crown-4 (B12C4) as both guest and host units are prepared. The copolymers exhibit highly selective sensitivities toward γ-cyclodextrin (γ-CD) and Na(+) . The presence of γ-CD induces the lower critical solution temperature (LCST) of PNB12 C4 copolymer to shift to a higher value due to the formation of 1:1 γ-CD/B12C4 host-guest inclusion complexes, while Na(+) causes a negative shift in LCST due to the formation of 2:1 "sandwich" B12C4/Na(+) host-guest complexes. Regardless of the complexation order, when γ-CD and Na(+) coexist with PNB12 C4 , competitive complexation actions of B12C4 as both guest and host units toward γ-CD and Na(+) finally form equilibrium 2:2:1 γ-CD/B12C4/Na(+) composite complexes, and the final LCST values of PNB12 C4 copolymer reach almost the same level. The results provide valuable guidance for designing and applying PNB12 C4 -based smart materials in various applications.

A metal-decorated nickel foam-inducing regulatable manganese dioxide nanosheet array architecture for high-performance supercapacitor applications.

Three dimensional manganese dioxide/Pt/nickel foam (shortened to MnPtNF) hybrid electrodes were prepared by double-pulse polarization and potentiostatic deposition technologies for supercapacitor applications. The decoration of Pt nanoparticles onto nickel foam varies the nucleation mechanism of the manganese dioxide species, inducing the formation of manganese dioxide nanosheets. Additionally, controlling the size of the Pt nanoparticles leads to modulated nanosheet architecture and electrochemical properties of the manganese dioxide electrode, as revealed by XRD, Raman spectra, SEM, TEM, cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. The nanosheet architecture of the MnPtNF electrode favors the transportation of electrons and ions, which results in the enhanced electrochemical properties. Importantly, the optimized MnPtNF electrode obtains a maximum specific capacitance of 1222 F g(-1) at 5 A g(-1) (89% of the theoretical specific capacitance of MnO2) and 600 F g(-1) at 100 A g(-1). Moreover, the presence of Pt nanoparticles in the MnO2 electrode effectively improves its cycling stability, which is confirmed by the increase of the specific capacitance retention from 14.7% to 90% after 600 cycles.