(745a) Vapor-Phase Transport As a Novel Route to Prepare Hyperbranched Aminosilica Hybrids

Silica-based inorganic–organic mesoporous hybrids are of growing interest due to their wide range of potential applications. Incorporation of organic functionalities into the silica framework has been achieved mostly via three synthetic routes: i) post-synthesis grafting of functional silanes, ii) direct co-condensation during synthesis, and iii) use of bridged organosilanes as precursors. In particular, functionalization of mesoporous silica with amino groups has been intensively studied because these materials can be applied for base-catalyzed reactions, adsorption of heavy metal cations, immobilization of bio-molecules, and CO₂ capture. Among others, our group has developed a simple way to prepare hyperbranched aminosilica (HAS) materials by ring-opening polymerization of aziridine in the presence of porous silicates in organic solvent media [1,2]. The HAS materials showed excellent performance in CO₂ capture from humid gas streams. In the previous report, the results suggested that the mesopores can become blocked or closed by aminopolymers, especially at the high organic loading [2]. In addition, functionalization of structural objects such as supported membranes and monoliths via liquid-phase polymerization is considered to be difficult to carry out on a large scale. In this presentation, we report a novel synthetic route to prepare HAS materials through vapor-phase transport. In this method, the aziridine monomers are transported into the solid in the vapor phase and subsequently polymerization is initiated at the silica surface. The obtained HAS materials had organic contents comparable to materials prepared via the conventional liquid-phase reactions. The amount of aminopolymers formed inside the pores was found to be affected by several synthesis parameters including temperature and reaction time. This novel method provides opportunities for efficient introduction of aminopolymers into other forms of supports including silica membranes and monolith.

References

[1] J. C. Hicks, J. H. Drese, D. J. Fauth, M. L. Gray, G. G. Qi, C. W. Jones, J. Am. Chem. Soc. 2008, 130, 2902-2903.

[2] J. H. Drese, S. Choi, R. P. Lively, W. J. Koros, D. J. Fauth, M. L. Gray, C. W. Jones, Adv. Funct. Mater. 2009, 19, 3821-3832.