Influence of MWNT and α-Tropolone on Thermal Stability and Crystallinity Behavior of Stereocomplexed Poly-l,d-lactides

Abstract

This paper reports the influence of MWNT and the deactivation of the tin(II)octanoate catalyst (catalyst used in the polymerization of lactides) by α-tropolone in poly-l,d-lactide stereocomplex. MWNT and α-tropolone were incorporated during a reactive extrusion process of l-lactide and d-lactide into poly-L,d-lactide. The materials prepared by microextrusion are characterized by transmission electron microscopy (TEM) and by 1H nuclear magnetic resonance (1H NMR). The thermal stability and the crystalline behavior analysis were conducted by thermogravimetry analysis (TGA) and by differential scanning calorimetry (DSC). This study shows the heterogeneous dispersion state of the MWNT in the poly-l,d-lactide matrix. The incorporation of MWNT reduces the conversion rate of monomer into polymer (94% without MWNT and 92% when MWNT were incorporated). Thermal characterization evidences the enhancement of thermal stability thanks to the incorporation of MWNT or α-tropolone when used separately. When they are combined together, the thermal stability is decreased. α-Tropolone and MWNT provide a nucleating effect on the stereocomplex crystalline phase and their combination does not modify their nucleating effect in poly-l,d-lactide.