Induced PEO Crystal Orientation within the Inversed Cylindrical Morphology of PEO-b-PS Block Copolymer

A poly(ethylene oxide)-\textit{block}-polystyrene (PEO-$b$-PS) diblock copolymer with a $M_{n}$ for the PS and PEO blocks being 7.7k and 20.1k g/mol, respectively, was studied by small and wide angle X-ray scattering. An inversed cylinder phase morphology was observed with the PS cylinders hexagonally distributed within the PEO matrix. Since the $T_{g}$ of the PS blocks ($\sim $30 \r{ }C) is lower than the $T_{m}$ of PEO crystal ($\sim $ 62 \r{ }C), the d-spacing of the inversed cylinder phase increased with increasing temperatures greater than 30 $^{o}$C. In the inversed cylinder morphology, the PEO is the major phase, and PS cylinders cannot confine the crystallization of PEO. However, $T_{c}$ dependent PEO crystal orientation changes are induced by the PS cylinders. Furthermore, different from the one-dimensionally preferred crystal orientations when $T_{c}$ is lower than 30 $^{o}$C, the PEO crystals are preferentially oriented in two dimensions when the $T_{c}$ is higher than 30 $^{o}$C in the inversed cylindrical morphology.