Phosphoric acid doped imidazolium silane crosslinked poly(epichlorihydrin)/PTFE as high temperature proton exchange membranes

Abstract

Low cost poly(epichlorohydrin) (PECH) was modified with imidazolium groups to prepare high temperature proton exchange membranes. Chloromethyl groups in the structure of the PECH benefit its modification with no need for highly toxic and carcinogenic chloromethylation reagents. Both methylimidazole (MeIm) and triethoxysilylpropyldihydroimidazole (SiIm) were used to carry out the S N 2 nucleophilic substitution for grafting the imidazolium groups onto the PECH. Meanwhile crosslinking of the modified PECH was achieved by forming a crosslinked silane network via the hydrolysis reaction of SiIm in an acid medium. Moreover, porous poly(tetrafluoroethylene) (PTFE) was used as the membrane matrix to enhance the mechanical strength of the fabricated membranes. The obtained PECH-SiIm-MeIm/PTFE membranes displayed phosphoric acid doping capacities of 110-170 wt% with low volume swelling ratios of less than 120%. Anhydrous proton conductivities of 0.010-0.063 S cm À1 were reached at elevated temperatures of 100-180 C by the membranes with adequate mechanical strength. Fuel cell tests demonstrated the technical feasibility of acid doped PECH-SiIm-MeIm/PTFE membranes for high temperature proton exchange membrane fuel cells.

Fabrication and investigation of phosphoric acid doped imidazolium siloxane crosslinked poly(2,6‐dimethyl‐1,4‐phenylene oxide) for high temperature polymer electrolyte membranes

“…With respect to the PPO‐100%SiIm‐Un polymer, several new peaks appear in the spectrum and are assigned as shown in Fig. . The above results indicate that the imidazolium (SiIm and MeIm) groups have been successfully introduced onto PPO polymer backbones.…”

“…The imidazole groups react with benzyl bromide groups of BPPO through an S N 2 type nucleophilic reaction, providing functional sites for PA doping via the anion–cation interaction. Meanwhile, the hydrolysis of siloxane moieties of SiIm in acidic conditions generate the siloxane crosslinked structure to enhance the mechanical and dimensional stabilities . The chemical structures of PPO, BPPO, PPO‐100%MeIm and PPO‐100%SiIm‐Un were characterized using 1 H NMR as shown in Fig.…”

“…The membranes were wiped with filter paper and then dried in a vacuum oven at 100 °C to remove water thoroughly and were weighed immediately to calculate the PA uptake. The PA doping ability was determined by both PA doping content and acid doping level (ADL) as previously reported . The corresponding equations are where W and W 0 are the membrane mass (g) with and without acid doping, respectively, and M is the average molecular weight (g mol −1 ) of various PPO‐ x %SiIm‐ y %MeIm membranes.…”

“…However, there are few reports on HT‐PEMs based on PPO derivatives . Inspired by previous work, we tried to design and prepare new HT‐PEMs based on imidazolium siloxane crosslinked PPO with excellent comprehensive performances. The imidazole groups in MeIm and SiIm reacted with the benzylbromide groups (–CH 2 Br) of BPPO in different mole ratios to obtain a series of imidazolium PPO membranes (PPO‐SiIm‐MeIm).…”

Synthesis and Investigation of the New Derivatives of Poly(Epichlorohydrin) Containing Energetic Groups

“…Many modifications have been done on PECH by different nucleophiles such as potassium 3,4,5-tris[4-(n-dodecan-1-yloxy)benzyloxy]benzoate [12], aliphatic potassium carboxylates [2], phenolate [4,13], amine [14], biphenyl carboxylic and naphthalene carboxylic acid derivatives [15], sodium methoxide [16], sodium azide [17], vinyl-terminated aromatic potassium carboxylate [18], aromatic and aliphatic thiol compounds [19], imidazolium groups [20], morpholine [21].…”