Organocatalytic synthesis of astaxanthin-containing poly(lactide)s

The synthesis of astaxanthin-containing poly(lactide)s is reported by the ring-opening polymerization of lactide initiated from residual alcohol groups on astaxanthin using a previously reported thiourea/tertiary amine catalyst. Polymers with molecular weights between 2500 and 30 000 g mol−1 are obtained with excellent levels of control, astaxanthin incorporation being confirmed by UV/Vis detected GPC, 1H NMR, MALDI-TOF MS and IR spectroscopic analysis. Study of the polymerizations at extended time periods revealed greatly increased levels of transesterification in comparison to polymerizations initiated by 4-pyrene-1-butanol, attributed to increased intramolecular transesterification side reactions.