2013 年 62 巻 4 号 p. 254-260
Wood flour (WF) was converted not only to carrier matrix for in situ synthesis of iron oxide nanoparticles but also to thermoplastic material by combination of anionic functionalization and benzylation. A sequence of procedure for the in situ synthesis of iron oxides includes ferrous ion-absorption of the chemically modified WF, precipitation of ferrous hydroxide by an alkaline treatment, and oxidation of the ferrous hydroxide. To facilitate the ferrous ion-absorption, we performed the anionic functionalization of WF via carboxymethylation or maleylation. The benzylation was expected to be favorable for improving thermoplasticity of the products. FT-IR spectroscopy revealed that the original hydroxyl groups were considerably substituted by the etherification and/or esterification. A successful incorporation of iron oxide particles (synthetic ferrites) into the anionically funcionalized WF matrix was confirmed by redox titrimetry. However, maleyl moieties incorporated after benzylation were largely hydrolyzed by the alkaline treatment for the in situ synthesis of iron oxides, which gave rise to an elution of ferric contents simultaneous with its formation. Such an elution could be prevented in part by the introduction of maleyl groups preceding benzylation. By means of the adequate set of chemical modifications, the original WF was transformed into a thermoplastic material. Actually, it was possible to mold the modified WF samples into a film form at a relatively low temperature of 140°C, even after the in situ synthesis of iron oxide. Magnetometry measurements revealed that the magnetic woody composite showed superparamagnetism (SPM) at room temperature. The unique magnetic character can be generally observed when the magnetic particles as dispersoid are loaded into the matrix on a scale of less than a few tens of nanometers. The formation of iron oxide nanoparticles was supported by field emission scanning electron microscopy and X-ray diffractometry. The observation of SPM may be of significance in the perceptibility to an external magnetic stimulus only on demand and without energy loss.