Polylactides with aldaric ester end groups or chain extending groups

The synthesis and characterisation of a series of poly(S,S-lactides) and poly(RR/SS-lactides) end capped or chain extended with aldaric ester groups are described. The aldaric esters are prepared from acetyl protected d-gluconolactone, d-galactonolactone and d-mannonolactone by ring opening with butanol or 1,4-butanediol, under acidic conditions. The aldaric esters are fully characterised, including by NMR spectroscopy and mass spectrometry. They are used as co-initiators, with an ethylzinc complex, to enable the controlled ring opening polymerisation of S,S- and rac-lactide. Thus, a series of polylactides are produced with various carbohydrate chain end or extending groups and are fully characterised, including by NMR spectroscopy and gel permeation chromatography (GPC). The polymerisation kinetics are examined, under pseudo first order conditions, and indicate that chain transfer reactions are occurring more rapidly than propagation reactions. The degradation kinetics of the polylactides are examined under acidic conditions; the aldaric esters increase the degradation rates compared to unfunctionalised end groups.