Synthesis of triazole-bearing polyethylene imine copolymers as water-free proton conducting membranes for PEM fuel cells

摘要

One of the main hurdles for commercialization of PEM Fuel cells is the need for ion conducting membranes capable of efficient water-free proton transport in the 1000C-2000C temperature range. A potential avenue to increase water-free conduction is to generate highly polar polymer matrices containing the proton conducting motifs as pendant groups. In order to probe the effect of backbone polarity on the heterocycle-mediated, water-free, proton conduction, we have synthesized a series of alkylated linear polyethylene imines containing triazole rings as the proton conducting groups.1,2 The target polymers (see Figure 1) were synthesized by improving previously reported methods and by developing a microwave assisted process to produce triazoles via a copper mediated “click” reaction of alkynes and sodium azide. These new polymers exhibited proton conductivities approximately 2 orders of magnitude higher than those of the analogous polysiloxanes with similar Tg’s and heterocycle content. These data suggests that incorporation of the ion conducting motifs within highly polar matrices is a promising approach to produce polymer membranes with proton conductivities within striking distance from the requirements for their use in PEM Fuel Cells.3 In order to evaluate the ion transport as a function of conductive domain morphology, this backbone will be incorporated into block copolymer architectures. Hemitelechelic precursor poly(2- ethyloxazoline), PEtOX, was synthesized via living CROP with PDI’s below 1.25.