Formation of Extended Ionomeric Network by Bulk Polymerization of L,D-lactide with Layered Double Hydroxide
Edward D. McCarthy, Mauro Zammarano, Douglas M. Fox, Ryan C. Nieuwendaal, Yeon S. Kim, P H. Maupin, Paul C. Trulove, Jeffrey W. Gilman
We report the formation of an ionomeric network in a poly(L,D-lactide) hybrid nanocomposite, (PLDLA-HYB) during in-situ melt polymerization of L,D lactide in the presence of magnesium/aluminium layered-double-hydroxide (LDH) without added catalyst. The effect of LDH mass loading and reaction time on molecular mass and yield of soluble poly(L,D lactide) (PLDLA-SOL) present in the hybrid was investigated for a better understanding of the conflicting roles of LDH in polymerization and degradation of PLDLA-SOL. High molecular mass PLDLA-SOL is obtained through initiation of polymerization by LDH. However an additional insoluble organic-inorganic fraction, INSOL, is also observed within the product when PLDLA-SOL is extracted using methylene chloride as solvent. It is proposed that INSOL is an ionomeric network comprising hydrogen-bonded, or otherwise co-ordinated, lactic acid monomer salts of magnesium, together with PLDLA in a 30 % to 70 % mass ratio.