title: Conformational behavior of dodecyldiamine inside the confined space of montmorillonites.
abstract: We have investigated the change of the intercalated amount and conformational behavior of dodecyldiamine (C(12)H(28)N(2), di-C(12)amine) inside the confined space of the montmorillonite (MMT) intergallery at different pHs of the intercalation solution (H(2)O/ethanol/Na(+)-MMT/di-C(12)amine), and these results were compared with those of dodecylmonoamine (C(12)H(27)N, mono-C(12)amine). The mono-C(12)amine with one end-functional amine (-NH(2)) has a constant intercalated amount independent of the pH of the intercalation solution, confirming the tail conformation in the MMT intergallery. On the other hand, the intercalated amount of di-C(12)amines remains quite low at low pH due to the long-range Coulombic repulsion among protonated amines. The di-C(12)amines dominantly take the bridge conformation inside the MMT intergallery up to pH 9.5 and adopt a fraction of the tail conformation at pH 11.5, which is verified by Fourier transform infrared spectra with an abrupt frequency shift of the CH(2) stretching band and the emergence of a new NH(2) scissoring band at 1598 cm(-)(1) related to unanchored free amines. The d-spacing and the square of the half-width at half-maximum of the MMT based on X-ray diffraction measurements are also constant up to pH 9.5, while these two variables are suddenly increased at pH 11.5. The bridge conformation of di-C(12)amines in the confined space of the MMT intergallery prevents poly(ethylene oxide) chains from intercalation into the MMT intergallery, called the gluing effect.
authors.affiliation: School of Chemical and Biological Engineering and Polymer Thin Films National Research Laboratory, Seoul National University, San 56-1, Shillim-dong, Kwanak-gu, Seoul 151-744, Korea.
authors.forename: Bongwoo
authors.initials: B
authors.lastname: Ha
authors.forename: Kookheon
authors.initials: K
authors.lastname: Char
mesh_terms: D000478:Alkylation; D000588:Amines / Q000737:chemistry*; D001546:Bentonite / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction
chemical_list: D000588:Amines; D001546:Bentonite