29Si, 27Al, 1H and 23Na MAS NMR Study of the Bonding Character in Aluminosilicate Inorganic Polymers

29Si, 27Al, 1H and 23Na solid-state magic-angle spinning (MAS) nuclear magnetic resonance (NMR) has been used to relate nominal composition, bonding character and compressive strength properties in aluminosilicate inorganic polymers (AIPs). The 29Si chemical shift varies systematically with Si-to-Al ratio, indicating that the immediate structural environment of Si is altering with nominal composition. Fast 1H MAS and 29Si TSiH/T1ρ relaxation measurements demonstrated that occluded pore H2O mobility within the disordered cavities is slow in comparison with H2O mobility characteristics observed within the ordered channel structures of zeolites. The 27Al MAS NMR data show that the Al coordination remains predominantly 4-coordinate. In comparison with the 29Si MAS data, the corresponding 27Al MAS line shapes are relatively narrow, suggesting that the AlO4 tetrahedral geometry is largely unperturbed and the dominant source of structural disorder is propagated by large distributions of Si–O bond angles and bond lengths. Corresponding 23Na MAS and multiple-quantum MAS NMR data indicate that Na speciation is dominated by distributions of hydration states; however, more highly resolved 23Na resonances observed in some preparations supported the existence of short-range order. New structural elements are proposed to account for the existence of these Na resonances and an improved model for the structure of AIPs has also been proposed.