Preparation and water desalination properties of bridged polysilsesquioxane membranes with divinylbenzene and divinylpyridine units

Bridged polysilsesquioxanes are promising materials for reverse osmosis membranes because they exhibit robust properties. To investigate the effects of the polarity and rigidity of organic components of the polymer on the water permeability of the membrane, two alkoxysilane monomers, 2,5-bis[2-(triethoxysilyl)vinyl]pyridine (BTES-VP) and 1,4-bis[2-(triethoxysilyl) vinyl]benzene (BTES-VB), were synthesized to compare their hydrophilicity and water desalination properties. Water contact angle experiments on the film surfaces revealed that the BTES-VP-derived film was more hydrophilic than the BTES-VB-derived film. Density functional theory calculations of the monomer structures also suggested that BTES-VP is more polar and has a larger dipole moment than BTES-VB. Both membranes prepared from BTES-VP and BTES-VB rejected 95-97% of aqueous sodium chloride and displayed water permeances of 1.1 x 10(-13) and 8.5 x 10(-14) m(3)/(m(2) Pa s), respectively.