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RESEARCH PRODUCT

Functionalized poly(butylene succinate) by nitroxide radical coupling

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In recent years there has been a growing interest in developing sustainable alternatives to oil-based plastics. In particular, biodegradable aliphatic polyesters, such as poly(lactic acid) (PLA) and poly(butylene succinate) (PBS), are becoming increasingly important due to their valuable properties including thermoplastic processability and thermo-mechanical properties. Nonetheless, these materials present several drawbacks, such as the lack of reactive functionalities that are limiting their applications, versatility and successful use as commodity plastics. In this work it was investigated for the first time a new method of preparation of functionalized PBS by a post-polymerization approach based on the radical coupling between PBS macroradicals and TEMPO derivatives carrying different functionalities. Our method turned out to be successful in promoting grafting by limiting the radical-induced crosslinking/branching of the polymer substrate (Fig. 1). In particular, two different series of functionalized PBS samples were obtained by grafting the 4-benzoyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl (BzO-TEMPO), and the pro-fluorescent 4-(1-naphtoate)-2,2,6,6-tetramethylpiperidine-1-oxyl (NfO-TEMPO). The grafting was clearly evidenced by MALDI-TOF MS, UV-Vis and 1H-NMR spectroscopy from which it was estimated the functionalization degree Moreover, by electron spinning resonance (EPR) experiments it was accurately determined the grafting site. Finally, the exploitation of a pro-fluorescent nitroxide to form functionalized PBS samples represents a significant step toward the unambiguous demonstration of the radical grafting on this type of polymers, proving also the possibility of tailoring a well-defined fluorescently labeled biodegradable polyester via a feasible process