Influence of quaternary amine organosilane structure on the formation and adsorption properties of surface-imprinted silicates

A series of quaternary ammonium functionalized. silicates surface imprinted with the soman hydrolysis product pinacolyl methylphosphonate (PMP) were f ormed in a one-pot procedure. The formation and adsorption properties of th ese materials were dependent on the alkyl chain length of the quaternary am ine. Brunauer-Emmett-Teller analysis and transmission electron microscopy r evealed that silicates formed with added quaternary amine functionalized or ganosilanes with 10 and 14 carbon hydrocarbon segments (N,N-didecyl-N-methy l-N-(3-trimethoxysilylpropyl)ammonium chloride (DDMAC) and N-tetradecyl-N,N -dimethyl-N-(3-trimethoxysilylpropyl)ammonium chloride (TDDMAC), respective ly) formed xerogels with surface areas of 630-712 m(2)/g and broad pore siz e distributions. The silicate that formed in the presence of a quaternary a mmonium functionalized organosilane with an 18 carbon alkyl chain (N-octade cyl-N,N-dimethyl-N-(3-trimethoxysilylpropyl)ammonium chloride (ODDMAC)) for med a microporous silicate with a lower surface area. Addition of PMP durin g synthesis did not affect the formation or adsorption properties of the DD MAC or TDDMAC silicates but resulted in an ODDMAC silicate with a higher su rface area. Significant differences in the adsorption capacities and equili brium binding constants of ODDMAC silicates formed with and without PMP wer e observed. This material demonstrated selectivity for small organophosphon ate monoesters over a bulkier organophosphonate monoester, diester, and met hyl parathion.