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.