Journal
MACROMOLECULAR MATERIALS AND ENGINEERING
Volume 288, Issue 1, Pages 44-49Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/mame.200290032
Keywords
nanocomposites; refractive index; rutile; TiO2; UV absorption
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Colloids of TiO2, where rutile was the only crystal modification which could be detected, with ca. 2.5 nm average particle diameter were synthesized by hydrolysis of TiCl4 in acidic solutions. The as-prepared particles were incorporated in polymers such as poly(vinyl alcohol) (PVAL), partially hydrolyzed poly(vinyl acetate) (PVAC88), polyvinylpyrrolidone, and poly(4-vinylpyridine). Nanocomposites transparent in the visible range were obtained. The highest TiO2 contents in such materials were achieved with PVAL and PVAC88, with TiO2 contents of ca. 35 wt.-% (i.e. 10.5 vol.-%). In particular, the nanocomposites with TiO2 contents above 24 wt.-% acted as efficient UV filters for radiation UP to ca. 360 nm. At very low TiO2 contents, an absorption maximum of the embedded TiO2 particles was observed at 225, ran with an extinction coefficient of 140 000 cm(-1) and a full width at half maximum of 45 nm, i.e. not only the absorption at the maximum at 225 nm but also at the flank of this band contributed significantly to the broadband UV absorption in the nanocomposites at higher TiO2 fractions. The incorporation of TiO2 enhanced the refractive index of the nanocomposites: for instance a refractive index of 1.609 was measured for a nanocomposite comprising 10.5 vol.-% TiO2 in PVAL, compared with 1.521 for the pristine polymer.
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