Polysilsesquioxanes with mixed self-assembled organic tethers: Alkyl chains and alkanoate-aminopropyl pairs

In order to increase the adsorption rate and to improve the endurance of the structure in the adsorption of transition metal pollutants on the lamellar polysilsesquioxane adsorbent RCOOH-NH2C3H6SiO1.5, we substituted a part of the RCOOH-NH2C3H6- with a simple alkyl chain, CnH2n + 2-. We prepared the polysilsesquioxane whose organic chains are 3-aminopropyl (NH2C3H6-) and linear alkyl (C16H33-, C18H37-, C20H42- and C22H46-) groups from 3-aminopropyltrimethoxysilane (APTMS) and alkyltrialkoxysilane/alkyltrichlorosilane, respectively, without degradation of the good lamellar structure. The silanes were condensed with alkaonate (C11H23COOH (LAS), C13H27COOH (MAS), C15H31COOH (PAS), C17H35COOH (SAS)) with the same amount as APTMS. The adsorption of Cu(II) from an aqueous solution was carried out for lamellar solids prepared from C18H37Si(OCH3)3, APTMS and MAS varying the C18H37Si(OCH3)3/APTMS ratio from 0/10 to 5/5. The adsorption rate increased by up to a factor of 91 due to the presence of alkyl chains from alkylsilane, while the capacity did not change significantly except for the ratio 5/5. The mechanism for inhibition of the degradation of the self-assembling structure by the presence of C18H37-chains is discussed.