Vapor-Phase Transport as A Novel Route to Hyperbranched Polyamine-Oxide Hybrid Materials

A new method to prepare hyperbranched polyamine-oxide hybrid materials by means of a vapor-phase transport is developed. In this method, hybrid materials having hyperbranched amine polymers covalently bound to an oxide support are formed by exposing the oxide support to the vapor of small nitrogen-containing heterocyclic monomers, in contrast to the conventional liquid-phase method, in which the support is dispersed in an organic solution containing monomer species. The aziridine and azetidine monomers are polymerized on the surface of the oxide supports (i.e., silica and alumina), resulting in poly(ethylenimine) or poly(propylenimine) chains attached to the porous solid support. The results suggest that the hybrid materials can be prepared over a wide range of preparation conditions with organic contents comparable to or even higher than those obtained from the standard liquid-phase method. It is demonstrated that supports with more acidity result in the hybrid materials with higher organic content. Interestingly, the resulting supported polyamines have lower molecular weights than the previously reported materials prepared by the liquid-phase method. It is anticipated that the vapor-phase synthesis can be applied for the efficient introduction of polyamines into structural forms of supports such as fibers, membranes, and monoliths, for which the liquid-phase method may be inappropriate or inefficient.