Abstract
Sequential phase transitions were investigated in detail for a set of newly designed poly(propylene oxide)-b-poly(ethylene oxide)-b-poly(propylene oxide) (PPO–PEO–PPO) triblock copolymers, where the PPO blocks have isotactic, (R)- or (S)-, or atactic configurations. Microphase separation and thermal composition fluctuations were studied near the order–disorder transition temperature (133 ± 1 °C), and the interaction parameters χ(T) were determined. A unique feature of these materials is the cooperative and sequential nature of phase transitions, which leads to the inversion of the crystallization/melting sequence of PEO and isotactic PPO blocks. The PEO blocks crystallize quickly (ca. 50 °C) within a soft, confined lamellar template, which is followed by slow crystallization of the isotactic PPO blocks (ca. 40 °C) under hard confinement. However, in the melting process, PEO crystals melt first (ca. 60 °C) affording soft confinement which enables isotactic PPO crystals to undergo recrystallization and lame...
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