Synthesis of α,ω-Primary Hydroxyl-Terminated Polyether Polyols Using Prussian Blue Analogs as Catalysts

Polyalkylene oxides and polyether polyols are the most frequently used raw materials in polyurethane production, and are commonly produced via the ring-opening polymerization of epoxides, particularly propylene oxide. However, the resulting polyols predominantly contain predominantly secondary hydroxyl groups (up to 95%) that are less reactive than those capped with primary hydroxyl groups, thereby limiting the applications of the former in polyurethane synthesis. In this study, a viable procedure for producing alpha,omega-primary hydroxyl-terminated polyols using various Prussian blue analogs as heterogeneous catalysts was developed. The reaction kinetics were first investigated to gain insight into the reactivity of primary and secondary alcohols in the ring-opening of epsilon-caprolactone. Subsequently, epsilon-caprolactone-capped polyols with predominantly primary hydroxyl groups were successfully synthesized via the ring-opening reaction of epsilon-caprolactone using polypropylene glycol as the macroinitiator. The reactivities of the resultant epsilon-caprolactone-capped polyols for polyurethane synthesis were greatly enhanced compared to those of conventional polyols.