First observation of an ordered microphase in melts of poly(oxyethylene)–poly(oxypropylene) block copolymers

Abstract

The first observation of ordered microphase structures in poly(oxyethylene)–poly(oxypropylene) diblock copolymers melts is reported. Two diblock copolymers were synthesised by anionic polymerisation, i.e. E₁₃₀P₅₈ and E₁₀₇P₆₉ where E represents an oxyethylene unit, OCH₂CH₂, and P an oxypropylene unit, OCH₂CH(CH₃). The volume fractions of the two components were in the range 0.5–0.6. Order in the melt phase was confirmed by small angle X-ray scattering, and order-to-disorder transitions (ODT) were located at 106°C (E₁₃₀P₅₈) and 114°C (E₁₀₇P₆₉). In a related experiment, a triblock copolymer with perdeuterated P blocks, E₃₃dP₄₂E₃₃, was synthesised and studied in the melt phase by small-angle neutron scattering. This allowed determination of the temperature dependence of the Flory–Huggins interaction parameter for the poly(oxyethylene)–poly(oxypropylene) system, i.e. χ=20.2/T+0.0221.