Synthesis of a sulfonamide functionalized poly(styrene oxide) and illustration of a potential post-polymerization strategy

Abstract

In the first part of our work, we demonstrate a design concept for the functionalization of styrene oxide (SO) with a sulfonamide protecting group. A (1S,2S)-(+)-[1,2-cyclohexanediamino-N,N′-bis(3,5-di-t-butylsalicylidene)]-chromium(III)chloride ((salen)Cr(III)) catalyst polymerizes the end grouped epoxide via ring-opening-polymerization (ROP) into the respective polyether backbone. Absolute molecular weights of the resulting homopolymers range between 14.2 to 113 kg mol⁻¹ with a polymer stability up to 300 °C and a glass transition temperature (T_g) of around 68–73 °C. The synthesis is completed by showing a possible post-polymerization modification of the functionalized poly(styrene oxide) (PSO). By adding the polymer to a lithium methoxide solution, a new reactive group in the form of a free sulfonate moiety can be generated. This method enables the transition towards a lithium sulfonated PSO that shows a thermal stability up to 300 °C and a T_g in the range of 18–20 °C.