Effect of molecular weight on cloud point of aqueous solution of poly (Ethylene oxide)– poly (propylene oxide) alternating multiblock copolymer

Abstract

A poly(ethylene oxide) (PEO)–poly(propylene oxide) (PPO) alternating multiblock (AMB) copolymer with various molecular weights was prepared via precipitation fractionation from an acetone/n-hexane mixture. The cloud point (Tc) of the aqueous solution of PEO–PPO AMB copolymer decreased as the number‐average molecular weight of the sample increased. This phenomenon is generally observed for certain homopolymer systems having a lower critical solution temperature, such as PEO/water and poly(N,N‐diethylacrylamide)/water systems. The relationship between the Tc of the solutions and the number of monomer units of the AMB copolymer suggests that the Shultz–Flory theory is applicable to this system.