Degradable Latexes by Nitroxide-mediated Aqueous Seeded Emulsion Copolymerization Using a Thionolactone

Thiocarbonyl addition-ring-opening polymerization of thionolactones offers a unique opportunity to incorporate thioester functions into vinyl polymer backbones via a radical mechanism. Recently, successful synthesis of degradable vinyl copolymer latexes based on dibenzo[c,e]oxepane-5-thione (DOT) has been reported by free-radical polymerization in aqueous emulsion and aqueous polymerization-induced self-assembly. Herein, to combine a controlled radical polymerization process with the avoidance of preliminary synthesis, we performed the aqueous nitroxide-mediated copolymerization of DOT and n-butyl acrylate (nBA) or styrene (S) via a two-step, ab initio emulsion process. nBA was first polymerized in water in the presence of the BlocBuilder alkoxyamine and DOWFAX 8390 as the surfactant to generate a stable aqueous suspension of living seeds of low molar mass PnBA-SG1. Seeded emulsion copolymerization was then performed via chain extension of the seeds at 110 °C for 8 h by a mixture of DOT and nBA (or S), leading to stable latexes with average diameters ranging from 120 to 320 nm. Successful degradations of the copolymers were achieved under basic conditions, which demonstrated the incorporation of labile thioester groups in the copolymer backbone.