Molecular Aggregation States and Physicochemical Properties of (Organic/Inorganic) Nanohybrids based on Aluminosilicate Nanotubes

ChEMS Seminar

Dr. Atsushi Takahara

Institute for Materials Chemistry and Engineering, Kyushu University

Organic/inorganic nanohybrids by dispersing inorganic nanostructures in organic matrices are attracting a great deal of research passion. Imogolite and halloysite are naturally occurring aluminosilicate minerals with a hollow nanotube structure. Imogolite is composed of single-wall nanotubes with stoichiometry of Al₂SiO₃ (OH)₄, where silanol (Si-OH) groups are in the inner part of the tube. Halloysite has a 1:1 Al:Si ratio and a stoichiometry oAl₂Si₂O₅(OH)₄.nH₂ O, with siloxane groups in the outside part of the tube. In this study, the authors propose several techniques for surface functionalization of imogolite and halloysite nanotubes and the preparation of novel polymer nanohybrids.

We introduced three approaches for dispersing imogolite nanotubes into synthetic polymer matrices, including both of the hydrophobic and the hydrophilic polymers, to prepare binary or ternary nanohybrids.^1,2 Due to the well dispersion and the transparency feature of imogolite itself, transparent polymer/imogolite nanohybrids were successfully prepared. Mechanical properties of the original polymers were improved by the interaction with imogolite. Moreover, the capability of imogolite for gel formation of biomolecules was demonstrated by fabricating imogolite nanotube-based enzyme and DNA hybrid hydrogels.

Selective hydrophobization of halloysite nanotube’s inner surface was demonstrated. Aqueous phosphonic acid was found to bind to alumina sites at the tube lumen and did not bind the tube’s outer siloxanesurface. Spectroscopic measurements of selectively modified tubes proved binding of octadecylphosphonic acid within the halloysite lumen through bidentate and tridentate P-O-Al linkage. Selective modification of the halloysite clay lumen creates an inorganic micelle-like architecture with a hydrophobic aliphatic chain core and a hydrophilic silicate shell. An enhanced capacity for adsorption of the modified halloysite toward hydrophobic derivatives of ferrocene was observed.³ Furthermore, Surface-initiated atom transfer radical polymerization (SI-ATRP) was performed through selectively adsorbed initiator with Dopa unit to  form  polymer brush into the nanotube lumen⁴

References

1.        W. Ma, W.O. Yah, H.Otsuka, A. Takahara,　Beilstein J. Nanotech.3, 82–100(2012).

2.        W. Ma, W.O. Yah, H. Otsuka, A. Takahara, J. Mater. Chem. DOI:10.1039/C2JM31570J.

3.        W. O. Yah, A. Takahara, Y. M. Lvov. J. Am. Chem. Soc. 134, 1853-1859(2012).

4.        W. O. Yah, H. Xu, H. Soejima, W. Ma, Y. Lvov, A. Takahara, J. Am. Chem. Soc., 134, 12134-12137(2012).