Novel hybrid poly(l-lactic acid) from titanium oxo-cluster via reactive extrusion polymerization

Abstract

This paper reports the synthesis of novel hybrid poly(lactic acid) by use of a titanium oxo-cluster, acting both as a catalyst and crosslinking agent of the polymer matrix. The already reported oxo-cluster Ti16O16(OEt)32 ([Ti]16) was synthesized and screened at the lab-scale as catalyst for the bulk polymerization of l-lactide (l-LA). [Ti]16 was found to be highly active for this reaction as up to 90% conversion in 30 min was obtained, affording PLLAs with Mn up to 65 000 g·mol−1 and relatively narrow dispersities (1.2–1.6). These polymerization reactions were further transposed to reactive extrusion process in which [Ti]16 oxo-cluster kept its high activity, affording hybrid-PLLA materials with Mn close to 58 000 g·mol−1 (some PLLAs could not be dissolved). Electronic micro-probe analysis of the resulting hybrid materials confirmed that the titanium oxo-cluster was well dispersed all over the PLLA matrix. Finally, it was shown that the hybrid PLLA containing [Ti]16 display superior dimensional stability under heat than commercial PLLA of same molar mass.