Towards the gemini cation anion exchange membranes by nucleophilic substitution reaction

As a critical component of alkaline fuel cells, anion exchange membranes determine the energy efficiency, output power density and the long term stability. Recently, the anion exchange membranes with gemini-cation side chains exhibit superior ion conductivity due to their good nanophase separation. However, the costly and complicated synthesis limits their scaling up and commercialization. To address this problem, a convenient synthetic procedure under mild conditions is well developed. A tertiary amine precursor is introduced onto the polymer by the nucleophilic substitution reaction to avoid the conventional chloro/bromo-methylation. Followed by a simple Menshutkin reaction with 6- bromo-N,N,N-trimethylhexan-1-am inium bromide, the polym er electrolytes are obtained in a high yield. The resulting anion exchange membranes with high conductivity, good fuel cell performance and restricted swelling suggest the potential for the application in fuel cell devices.

Tetrazole tethered polymers for alkaline anion exchange membranes

Poly（2,6-dimethyl-l,4-phenylene oxide） was tethered with a 1,5-disubstituted tetrazole through a quaternary ammonium linkage. The formation of a tetrazole-ion network in the resulting polymers was found to promote the hydroxide ion transport through the Grotthus-type mechanism.

Preparation of click-driven cross-linked anion exchange membranes with low water uptake

Significant advancement in anion exchange membrane(AEM)fuel cell(AEMFC)technology is important in the field of renewable energy.AEMs with comb-shaped architectures have attracted considerable research interest because of some unique features,including high anion conductivity,low swelling,and high alkaline stability.Here,we report preparation,characterization,and performance evaluation of a novel comb-shaped cross-linked AEM synthesized by the thiol-ene click and Menshutkin reactions.The prepared ionomer decreases the trade-off between the water uptake and the conductivity.The thiol-ene click reaction was used to synthesize the 1,14-di(1H-imidazol-1-yl)-6,9-dioxa-3,12-dithiatetradecane(IDDT)cross-linker.IDDT was then introduced into the brominated poly(2,6-dimethyl-1,4-phenylene oxide)backbone by the Menshutkin reaction.The prepared ionomers show high thermomechanical stability,which is needed in AEMFC technology.The CLINK-15-100 membrane(ion exchange capacity 1.23 mmol/g)shows relatively good conductivities of 19.66 and 34.91 mS/cm at 30 and 60℃,respectively.Interestingly,the membrane shows water uptake of only 14.22%at room temperature,which is considerably lower than many previously reported membranes.After 16 days of alkaline treatment in 1 M NaOH solution at 60℃,the CLINK-15-100 membrane retains 77%of its initial conductivity,which is much better than the traditional quaternized poly(2,6-dimethyl-1,4-phenylene oxide)membrane.

Fast Bulky Anion Conduction Enabled by Free Shuttling Phosphonium Cations

Highly conductive anion-exchange membranes(AEMs)are desirable for applications in various energy storage and conversion technologies.However,conventional AEMs with bulky HCO_(3)^(-)or Br-as counterion generally exhibit low conductivity because the covalent bonding restrains the tethered cationic group’s mobility and rotation.Here,we report an alternative polyrotaxane AEM with nontethered and free-shuttling phosphonium cation.As proved by temperature-dependent NMR,solid-state NMR,and molecular dynamics simulation,the phosphonium cation possesses a thermally trigged shuttling behavior,broader extension range,and greater mobility,thus accelerating the diffusion conduction of bulky anions.Owing to this striking feature,high HCO_(3)^(-)conductivity of 105 mS cm^(-1)at 90℃ was obtained at a relatively lower ion-exchange capacity of 1.17 mmol g^(-1).This study provides a new concept for developing highly conductive anion-exchange membranes and will catalyze the exploration of new applications for polyrotaxanes in ion conduction processes.

Fast Bulky Anion Conduction Enabled by Free Shuttling Phosphonium Cations

Highly conductive anion-exchange membranes(AEMs)are desirable for applications in various energy storage and conversion technologies.However,conventional AEMs with bulky HCO3-or Br-as counterion generally exhibit low conductivity because the covalent bonding restrains the tethered cationic group’s mobility and rotation.Here,we report an alternative polyrotaxane AEM with nontethered and free-shuttling phosphonium cation.As proved by temperature-dependent NMR,solid-state NMR,and molecular dynamics simulation,the phosphonium cation possesses a thermally trigged shuttling behavior,broader extension range,and greater mobility,thus accelerating the diffusion conduction of bulky anions.Owing to this striking feature,high HCO_(3)-conductivity of 105 mS cm^(-1) at 90℃ was obtained at a relatively lower ion-exchange capacity of 1.17 mmol g^(-1).This study provides a new concept for developing highly conductive anion-exchange membranes and will catalyze the exploration of new applications for polyrotaxanes in ion conduction processes.