Kikku Fukushima Winkler - Polylactic Acid and Polylactic Acid-Based Nanocomposite Photooxidation

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  Publication Details (including relevant citation   information):

  Sergio Bocchini, Kikku Fukushima, Alessandro Di Blasio, Alberto   Fina, Alberto Frache, Francesco Geobaldo, Biomacromolecules,  11, 2919-2926,   (2010).



  The importance of photooxidation in promoting formation of   anhydride functional groups and thus promoting   hydrolysis/biodegradation of polylactic acid and PLA   nanocomposites were elucidated. PLA-based nanocomposites were   prepared by adding 5% wt filler content of sodium montmorillonite   (ClNa), sodium montmorillonite partially exchanged with Fe(III)   (ClFe), organically modified montmorillonite (Cl20A), unmodified   sepiolite (SEP), and fumed silica (SiO2). The pure PLA and   nanocomposites were UV-light irradiated in artificial accelerated   conditions representative of solar irradiation (λ >   300 nm) at 60 °C in air. The chemical modifications resulting   from photooxidation were followed by IR and UV-visible   spectroscopies. The infrared analyses of PLA photooxidation show   the formation of a band at 1845 cm-1 due to the formation of   anhydrides. A photooxidation mechanism based on hydroperoxide   decomposition is proposed. The mechanism proposed is confirmed by   an increase in anhydride formation rate: the main responsible for   this acceleration was identified as transition metals contained   in the nanofillers as impurities and involved in the catalytic   hydroperoxide decomposition.

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