Cationic copolymerization of tetrahydrofuran with propylene oxide. VII. Effect of water on the reaction

Abstract

Propylene oxide (PO) and tetrahydrofuran (THF) were copolymerized at 0°C using boron trifiuoride etherate as catalyst, water as cocatalyst, and ethylene dichloride as solvent. The initial rates of consumption of PO and THF were found to vary as follows with the initial catalyst, cocatalyst, and comonomer concentrations:(Formula Presented) and (Formula Presented) Computations of reactivity ratios yielded values of 0.26 for PO [M1] and 0.80 for THF [M2] when the initial PO to THF molar ratio was greater than one, suggesting the formation of copolymer rich in alternating species. When the same ratio was less than one, the reactivity-ratio values increased to 1.96 for PO and 2.40 for THF, suggesting the formation of both homopolymers and copolymer from the comonomer mixture. Molecular weights of the reaction products varied from 283 to 1420. The unusually low values are attributed to the presence of water and to transfer reactions which are believed to terminate propagation chains at an early stage. © 1975 The Society of Polymer Science, Japan.