Self-assembly of amphiphilic alkyloligosiloxanes within cylindrically and spherically confined spaces

The self-assembly of amphophilic alkyloligosiloxane molecules within cylindrically and spherically confined spaces has been investigated. Hydrolyzed solutions of the precursors consisting of an alkylsiloxane core and three branching trimethoxysilyl groups (C_nH_2n+1Si(OSi(OMe) ₃)₃, n = 10 and 16) were impregnated into the cylindrical pores of porous anodic alumina membranes (PAAMs), leading to the formation of rod- and tubelike hybrids. A two-dimensional (2D) hexagonal mesostructure with a circular orientation and a lamellar mesostructure with a multitubular orientation were confirmed for n = 10 and 16, respectively. The pore diameters of PAAMs ranging from 30 to 400 nm did not significantly affect the mesostructures of the hybrids. The self-assembly in the spherical droplets was also performed by spray-drying of the hydrolyzed solutions. At high temperature, vesicular lamellar mesostructures were formed, independent of the alkyl chain length of the precursors (n = 10 or 16). Spherical hybrids with a core-shell structure (a 2D hexagonal core and a lamellar shell) were also prepared by lowering the drying temperature in the case of n - 10. These are the first findings on the confined assembly of single siloxane-based amphiphiles that will lead to the fabrication of novel hierarchically ordered hybrid materials having Si-C covalent bonds at the interfaces.