Polyreaction of l-lactide with 11-hydroxyundecylphosphonic acid – A mixed polymerization – Condensation process leading to functionalized PLAs

This work describes the polymerization of L-lactide (LA) carried out in the bulk (180 o C) using 11-hydroxyundecylphosphonic acid (UND) as a single molecule cationic catalyst – initiator (CINICAT). In contrast with the previously published research from this field, where the polymerization and potential condensation processes were separated, in the studied conditions the ring opening polymerization of LA and the condensation involving the hydroxyl end – groups reacting with acidic groups of the UND catalyst are simultaneous. It will be shown that in a closed system after the initial period of this process most of the geminal acidic groups of the UND CINICAT have already reacted and the concentration of the formed mono acidic groups reaches plateau. The released H 2 O almost quantitatively initiates the growth of new PLA chains, and the obtained dependence of the monomer conversion on time is close to linear. The obtained polylactide (PLA) macromolecules with reactive acidic groups along the chains may further be functionalization – for example by the reaction with epoxide rings. Alternatively, a further condensation with a deliberate removal of H 2 O from the system is possible, leading to the PLAs of higher molecular weight values.