Well-Defined Azlactone-Functionalized (Co)polymers on a Solid Support: Synthesis via Supported Living Radical Polymerization and Application as Nucleophile Scavengers

Abstract : Wang resin has been converted to a supported initiator for transition metal-mediated living radical polymerization often called atom-transfer radical polymerization (ATRP) of 2-vinyl-4,4-dimethyl-5-oxazolone (VDM) and styrene (S). Several “Rasta” resins with well-defined macromolecular architectures, including homopolymers PVDM, PS, statistical P(S-stat-VDM), block P(S-b-VDM), and P[S-b-(S-stat-VDM)] copolymers, have been elaborated. For the homopolymerization of VDM and S, a sacrificial initiator, benzyl 2-bromoisobutyrate (BBI), has been introduced to monitor the evolution of molar masses and polydispersity indexes (PDIs) of PS and PVDM onto the Wang resin support without cleavage. After 6 h, 86.7% conversion of VDM is reached, with the isolated PVDM chains having a molar mass of 18 000 g mol-1 and a PDI value of 1.22. Block copolymers have been synthesized in two steps, involving the synthesis of the PS block isolated at low conversions (<15%) to maintain the bromine end-chain functionality and the subsequent synthesis of the second PVDM or P(S-stat-VDM) block. Polydispersity indexes of the cleaved (co)polymers were low (PDI = 1.11−1.44), and high azlactone loadings have been reached (loading = 6.0 mmol g-1). Such azlactone-functionalized Wang resins have shown high efficiency during the scavenging process of benzylamine as monitored by HPLC. Moreover, grafted statistical copolymers have shown the best behavior for removing benzylamine because of an improvement of the accessibility of azlactone rings by the dilution with styrene units.