A rare example of the formation of polystyrene-grafted aliphatic polyester in one-pot by radical polymerization

The radical copolymerization of cyclic ester β-propiolactone (β-PL) with styrene (St) at 120 °C, with a complete range of monomer ratios, is a rare example of a system providing graft copolymers (PSt-g-β-PL) in one pot. The structure of the resulting β-PL-St copolymers was proven by using a combination of different characterization techniques, such as 1D and 2D NMR spectroscopy and gel permeation chromatography (GPC), before and after alkaline hydrolysis of the polymers. The number of grafting points increased with an increasing amount of β-PL in the feed. A significant difference in the reactivity of St and β-PL and radical chain-transfer reactions at the polystyrene (PSt) backbone, followed by combination with the active growing poly(β-PL) chains, led to the formation of graft copolymers by a grafting-onto mechanism.