New Stereocomplex PLA-Based Fibers: Effect of POSS on Polymer Functionalization and Properties

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• 作者：Orietta Monticelli ; Matilde Putti ; Lorenza Gardella ; Dario Cavallo ; Andrea Basso ; Mirko Prato ; Simone Nitti
• 刊名：Macromolecules
• 出版年：2014
• 出版时间：July 22, 2014
• 年：2014
• 卷：47
• 期：14
• 页码：4718-4727
• 全文大小：466K
• ISSN：1520-5835

文摘

In this work, a novel approach for the functionalization of electrospun stereocomplex polylactide (sc-PLA)-based fibers, prepared from solutions containing equimolar amount of high-molecular-weight poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA), was developed. The method, which consists in introducing functionalized polyhedral oligomeric silsesquioxanes (POSS) into the electrospinning solutions, was carried out by employing as a solvent system a 2:1 mixture of chloroform (CHCl₃) and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), never applied in the production of sc-PLA fibers, which was found to promote POSS solubilization while simultaneously allowing to obtain an excellent fiber homogeneity. Indeed, the specific effect of the single components of the solvent mixture, CHCl₃ and HFIP, on fiber structuring and morphology was evaluated. Conversely to the fiber morphology, which turned out to be significantly affected by the chosen electrospinning solvent, the PLA stereocomplexation, occurring upon subsequent annealing treatment at 100 掳C (as evidenced by differential scanning calorimetry (DSC) and X-ray diffraction analyses), was found to be similar for fibers prepared starting from the different types of solvent. Unlike solution casting, electrospinning allows the exclusive formation of stereocomplex crystallites, simultaneously promoting a submicrometric dispersion of the silsesquioxanes, with the consequent fiber functionalization. In our work, two different kinds of POSS鈥攐ne characterized by hydroxyl groups (POSS鈥揙H) and another one functionalized with an amino-bearing molecule (POSS鈥揘H₂)鈥攚ere exploited to impart hydroxyl and amino functionalities to PLA based nanofibers, while preserving the capability of the polymer system to form a pure stereocomplex on subsequent annealing. In particular, it was found that the amino groups of the sc-PLA fibers functionalized with POSS鈥揘H₂, promote specific interactions with a metal precursor, i.e., PdCl₂, which, as a result of a subsequent reduction, forms metal nanoclusters homogeneously dispersed on the fiber surface. The higher thermal and chemical resistance of the sc-PLA fibers with respect to those based solely on PLLA allowed to significantly broaden the applications of the catalytic system. Indeed, the sc-PLA/Pd fibers turned out to be very active in the Heck reaction, easily recoverable and reusable for multiple catalytic cycles.