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Incorporation of iron(0) complex into polymer-grafted silica and colloidal crystallization in organic solvent were studied.
In this study, zero-valence iron complex, vinylferrocene (Vfc) and iron(0)tricarbonyl(4,4-dimethyl-1,-4-cyclohexadienyl)
acrylate (Fe(0)Ac) or methacrylate (Fe(0)Me), were introduced into grafted polymer to prevent from increasing ionic
strength in colloidal crystallization system. Poly(methyl methacrylate (MMA)-co-Vfc)-grafted silica never formed
colloidal crystals in polar solvent, such as acetone or acetonitrile. However, increasing ferrocenyl group fraction in the
polymer resulted in disturbing the crystallization. Poly(N-isopropylacrylamide (NIPAAm)-co-Vfc)-grafted silica, which
was composed of mole fraction of Vfc, 1/3, afforded crystallization in ethanol over the particle fraction of 0.053. In the
case of diene-Fe(0)(CO)3/polymer-grafted silica, poly(MMA-co-Fe(0)Ac)-, poly(NIPAAm-co-Fe(0)Ac)- and poly(N.N-dimethylacrylamide
(DMAAm)-co-Fe(0)Ac)-grafted silica gave colloidal crystallization in relatively low polar solvents,
DMF, acetone, acetonirile and ethanol, critical volume fraction for which were in the range from 0.054 to 0.117. In the
case of copolymer-grafted silica containing Fe(0)Me, poly(MMA-co-FeMe)-grafted silica crystallized in DMF,
Interestingly, especially in cases of polymer-grafted silica containing Fe(0)Ac or Fe(0)Me composed of the highest mole
fraction Fe(0)Me, 1/2, afforded crystallization in DMF. The iridescence color of the colloidal crystals was changed with
the combination of grafted polymer and solvent. The characteristic coloration of the solution from reddish to greenish
color is possibly due to absorption of blue light region by diene-Fe(0)(CO)3 complex and Bragg deflection on colloidal
crystals.
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