A. Khanal K. Nakashima N. Kawasaki Y. Oishi M. Uehara H. Nakamura Y. Tajima Fabrication of organic–inorganic nano-complexes using ABC type triblock copolymer and polyoxotungstates Received: 12 October 2004 Accepted: 24 December 2004 Published online: 11 May 2005 Ó Springer-Verlag 2005 Abstract New organic–inorganic nano- complexes were produced from a micelle of tri-block polymers; poly(styrene)-b- poly(2-vinylpyridine)- b-poly (ethylene oxide) (PS-PVP-PEO) and tungsten compounds such as tungstate (W 1 2) ), undecatungstophospate (PW 11 7) ) and undecatungstosilicate (SiW 11 8) ) in acidic aqueous solutions. The size and morphology of the complexes were characterized by measurements of dynamic light scattering, atomic force microscopy, and scanning electron microscopy. This complex is assembled mainly by the charge interaction between the inorganic polyanions and the posi- tively charged PVP block in the PS-PVP- PEO molecule, which was confirmed by zeta-potential and fluorescence spectro- scopic studies. In the absence of the inorganic anions, the zeta-potential of the micelle was +11 mV at pH 3 due to the positive charge of the PVP block. When the inorganic anion was mixed with the PS-PVP-PEO micelle, decrease in the zeta-potential due to charge neu- tralization occurred with incorporation of inorganic anions into the PS-PVP- PEO micelle. The minimum zeta-poten- tial was 0, )33, and )35 mV for W 1 2) / PS-PVP-PEO, PW 11 7) /PS-PVP-PEO, and SiW 11 8) /PS-PVP-PEO complexes, respectively. Excess negative charge which occurred in the latter two complexes indicates that PS-PVP-PEO molecules bound PW 11 7) and SiW 11 8) by forces other than charge interaction. In addition, the incorporation of an inorganic polyanion into the micelle gave a new morphology to the micelle. In the absence of the polyanion, the PS-PVP- PEO micelles showed an extended conformation due to repulsive forces working among the positively charged PVP blocks. Addition of the polyanion caused the formation of shrunken forms of the micelles, since the charge repulsion was cancelled by the polyanion. This feature may be useful in developing a new type of functioning micelle. Keywords Polyoxotungstate Æ Undeca- tungstophospate Æ Undecatungstosili- cate Æ Tungstate Æ Poly(styrene)-b- poly(2-vinylpyridine)-b-poly(ethylene oxide) Colloid Polym Sci (2005) 283: 1226–1232 DOI 10.1007/s00396-005-1302-9 SHORT COMMUNICATION A. Khanal Æ K. Nakashima (&) N. Kawasaki Æ Y. Oishi Department of Chemistry, Faculty of Science and Engineering, Saga University, Honjo, Saga, Saga 840-8502, Japan E-mail: nakashik@cc.saga-u.ac.jp Tel.: +81-952-288850 Fax: +81-952-288548 M. Uehara Æ H. Nakamura Micro-chemical Processing Group, National Institute of Advanced Industrial Science and Technology, Tosu Saga 841-0052, Japan Y. Tajima Infection Control Sciences, Postgraduate School of Medicine, Juntendo University, Hongo, Bunkyo-ku, Tokyo 113-8421, Japan Abbreviations PW 11 7) Undecatungstophosphate, (PW 11 O 39 ) 7) SiW 11 8) Undecatungstosilicate, (SiW 11 O 39 ) 8) W 1 2) Tungstate (WO 4 2) ) POT(s) Polyoxotungstate(s) PS- PVP- PEO Poly(styrene)-b-poly (2-vi- nylpyridine)-b-poly(ethyl- ene oxide) ADN Apparent degree of neu- tralization DLS Dynamic light scattering AFM Atomic force microscopy SEM Scanning electron micros- copy EPM Electrophoretic mobility Py Pyrene