Gas permeability of cross-linked poly(ethylene-oxide) based on poly(ethylene glycol) dimethacrylate and a miscible siloxane co-monomer

Pure gas permeability coefficients of a series of copolymers based on polar, hydrophilic poly(ethylene glycol) dimethacrylate, n = 14 (PEGDMA) and siloxane-based co-monomer, [methyl bis(trimethylsiloxy)silyl] propyl glycerol methacrylate (SiGMA) are reported. SiGMA is miscible with PEGDMA and able to form homogeneous films. SiGMA contains a bulky siloxane-based end group, which acts to increase permeability, and an -OH pendant group, which increases miscibility with polar co-monomers, such as PEGDMA. As the SiGMA content in these copolymers increases to 53 vol%, CO2 permeability increases from 95 to 255 barrer, while CO2/N2 and CO2/H2 pure gas selectivities decrease from 58 to 20 and 6.4 to 3.2, respectively. At the same time, fractional free volume of the copolymer increases from 0.118 to 0.140. Comparisons to a similar copolymer system are made to rationalize the permeability and selectivity trends of this series of copolymers.