Preparation and characterization of polymer electrolyte membranes based on silicon-containing core-shell structured nanocomposite latex particles

A series of silicon-containing core-shell structured polyacrylate/2-acrylamido-2-methyl-1-propanesulfonic acid (SiO2-CS-PA/A) nanocomposite latex particles are prepared by the emulsifier-free emulsion polymerization of acrylate monomers and various amount of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) with colloidal nanosilica particles as seed. The chemical and morphological structures of latex particles with high monomer conversion are determined using Fourier transform infrared (FTIR), dynamic light scattering (DLS) and transmission electron microscopy (TEM). The SiO2-CS-PA/A nanocomposite membranes are fabricated through pouring the latex onto a clean surface of glass and drying at 60 °C for 10 h and 120 °C for 2 h. The nanocomposite membranes possess good thermal and dimensional stability. In addition, in comparison to Nafion® 117, the nanocomposite membranes exhibit moderate proton conductivity, significantly better methanol barrier and selectivity. The methanol diffusion coefficient is in the range of 1.03 × 10−8 to 5.26 × 10−8 cm2 s−1 which is about two orders of magnitude lower than that of Nafion® 117 (2.36 × 10−6 cm2 s−1). The SiO2-CS-PA/A 5 membrane shows the highest selectivity value (2.34 × 105 S cm−3) which is approximately 11.0 times of that (2.13 × 104 S cm−3) of Nafion® 117. These results indicate that the nanocomposite membranes are promising candidates to be used as polymer electrolyte membranes in direct methanol fuel cells.