Fabrication of a 2,6-diaminopurine-grafted cellulose nanocrystal composite with high proton conductivity

In this study, 2,6-diaminopurine was successfully grafted onto cellulose nanocrystal (CNC) backbones based on the FT-IR and solid-state C-13 NMR analysis, thus producing a novel proton conductive membrane combined with excellent performance of CNCs and proton conductivity of purines. The highest degree of substitution of the modified materials reached 18.04% when the molar ratio of anhydroglucose units to 2,6-diaminopurine was 1: 2. These biodegradable membranes are highly expected to be a green alternative for conductive materials, showing high proton conduction up to 0.222 S cm(-1) at high temperatures (100 degrees C), which was superior to that of the pure CNC membranes (0.019 S cm(-1) at 100 degrees C). The composite films doped with oxidized CNCs showed an improved tensile strength of up to 91.35 MPa and the value of Young's modulus decreased about 10 times, indicating a higher mechanical strength and flexibility. Moreover, the composite membranes had good thermal stability and better methanol permeability (1.41 x 10(-7) cm(2) s(-1)) than that of a commercial membrane (2.09 x 10(-6) cm(2) s(-1)).

Automated summary

In this study, 2,6-diaminopurine was successfully grafted onto cellulose nanocrystal (CNC) backbones to create a novel proton conductive membrane. This membrane exhibited high proton conduction at elevated temperatures, superior mechanical strength and flexibility, and good thermal stability and methanol permeability.