Kazuya Yamamoto

Transparent polymer nanohybrid prepared by in situ synthesis of aluminosilicate nanofibers in poly(vinyl alcohol) solution

Polymer nanohybrid materials that consist of poly(vinyl alcohol)(PVA) and aluminosilicate nanofiber imogolite were prepared by effective dispersion of aluminosilicate nanofiber in a polymer matrix by an synthetic method. The as-synthesized imogolite-PVA hybrid was characterized by infrared spectroscopy, wide angle X-ray diffraction and atomic force microscopic observations. The imogolite-PVA hybrid film was highly transparent compared with imogolite-PVA blend film, which was prepared by a solution blend of the freeze-dried imogolite powder with PVA. In addition, compared with PVA film, the hybrid films showed an increase in the elastic modulus and heat distortion temperature. These results indicate that synthesis of imogolite in PVA solution successfully formed the polymer nanohybrid with finely-dispersed nanofillers.

Imogolite Reinforced Nanocomposites: Multifaceted Green Materials

This paper presents an overview on recent developments of imogolite reinforced nanocomposites, including fundamental structure, synthesis/purification of imogolite, physicochemical properties of nanocomposites and potential applications in industry. The naturally derived nanotubular material of imogolite represents a distinctive class of nanofiller for industrially significant polymer. The incompatibility between the surface properties of inorganic nanofiller and organic matrix has prompted the need to surface modify the imogolite. Early problems in increasing the binding properties of surface modifier to imogolite have been overcome by using a phosphonic acid group. Different approaches have been used to gain better control over the dispersal of nanofiller and to further improve the physicochemical properties of nanocomposites. Among these, polymer grafting, in situ synthesis of imogolite in polymer matrix, and spin-assembly are some of the promising methods that will be described herein. This imogolite reinforced nanocomposite of enhanced optical and mechanical properties, and with unique biological and electronic properties, is expected to become an important category of hybrid material that shows potential for industrial applications.

Preparation of a novel (polymer/inorganic nanofiber) composite through surface modification of natural aluminosilicate nanofiber

Imogolite is one of the aluminosilicates with a chemical formula of Al 2 O 3 SiO 2 (H 2 O) n , consisting of hollow nanotubes with an external diameter of about 2.5 nm and a length from several hundred nanometers to a micrometer. Atomic force microscopic (AFM) observation revealed that the imogolite molecules form a fibrous network at pH=3.0. Since the outer surface of imogolite consists of the Al-OH group, a strong interaction can be expected between the Al-OH and the -PO(OH) 2 groups. Octadecylphosphonic acid (OPA) was chosen as a model amphiphilic molecule, and it chemisorbed onto the surface of imogolite. Surface coverage of imogolite with OPA was confirmed by infrared spectroscopy, thermogravimetric analysis, and adhesion force measurement by (AFM). The OPA-chemisorbed imogolite was dispersed in hexane whereas it forms precipitates in water. Since imogolite engages in a specific interaction with -PO(OH) 2 groups, it is expected that imogolite can be molecularly dispersed in -PO(OH) 2 group-modified poly(vinyl alcohol) (PVA). Temperature dependence of dynamic viscoelasticity exhibited a higher temperature shift of the α a -absorption of the matrix phosphorylated PVA for the (imogolite/phosphorylated PVA) hybrid compared with that for phosphorylated PVA.