Differences in Crystallization Behaviors between Cyclic and Linear Polymer Nanocomposites

Cyclic polymers exhibit fascinating crystallization behaviors owing to the absence of chain ends and more compact conformations.In the current simulation,dynamic Monte Carlo simulations were performed to reveal the underlying mechanism of the effect of chain topology and chain length on crystallization of polymer in solutions containing one-dimensional nanofiller.Simulation results suggested that the filled cyclic polymers exhibit higher melting temperature,higher crystallization temperature,and faster crystallization rate than the analogous linear polymers of identical chain length,especially in the systems with relatively short chains.Based on the Thomson-Gibbs equation,we theoretically analyzed the difference in the melting point between the cyclic and linear polymers under different chain lengths,and derived the dependence of the ratio of the melting point of the linear polymers to that of its cyclic analogs on chain length.In addition,it was also observed that the nanofiller can induce the formation of nanohybrid shish-kebab structure during isothermal crystallization of all systems.

Reinforcing oxygen electrocatalytic activity via selective dualphase heterointerface engineering for rechargeable Zn-air batteries

Dual-phase heterointerface electrocatalysts(DPHE)constructed by oxygen reduction reaction(ORR)-and oxygen evolution reaction(OER)-active elements exhibit excellent bifunctional activity and long-term durability due to the abundant interface exposure and synergistic catalytic effect.Herein,low-dimensional N-doped graphene nanoribbons(N-GNRs)coupling with ultrathin CoO nanocomposites(N-GNRs/CoO)were controllably fabricated through a facile two-step approach using synthesized Co(OH)_2 nanosheet as CoO precursor.Density functional theory(DFT)calculations and experimental characterizations prove that the formation of interface between N-GNRs and CoO can induce local charge redistribution,contributing to the improvement of catalytic activity and stability.The optimal N-GNRs/CoO DPHE possesses hierarchically porous architectures and presents outstanding bifunctional activities with a small potential gap of 0.729 V between the potential at 10 mA·cm^(-2)for OER and the halfwave potential for ORR,which outperforms Pt/C+IrO_(2)and the majority of noble-metal-free bifunctional catalysts.Liquid-and solid-state rechargeable Zn-air batteries assembled with N-GNRs/CoO as the cathode also display high peak power density and fantastic cycle stability,superior to that of benchmark Pt/C+IrO_(2)catalyst.It is anticipated to offer significant benefits toward high activity,stability and mechanical flexibility bifunctional oxygen electrocatalysts for rechargeable Zn-air batteries.