Poly(ethylene oxide) Crystal Orientation Change under 1D Nanoscale Confinement using Polystyrene-block-poly(ethylene oxide) Copolymers: Confined Dimension and Reduced Tethering, Density Effects

In this study we systematically investigated the effects of confined dimension (the thickness of PEO layer) and reduced tethering density (delta(REO), defined by sigma pi R-g(2), where sigma is the tethered chain density and R-g is the radius of gyration of the tethered PEO chain in its end-free state in the melt) on the PEO crystal orientation change within a ID nanoscale confinement We realized this confinement by utilizing two symmetric polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymer single crystals grown at different crystallization temperatures(T-x) in dilute Solution via the self-seeding technique After the single crystals were collected as mats, the thicknesses of both the PEO single crystal (d(PEO)) and I'S glassy layer were measured using small-angle X-ray scattering (SAXS) coupled to the I D correlation function. Because T-g(15)PS higher than T-m(PEO) in those PS-b-PEO single crystal Mats. 1D confinements having different d(PFO) and 5 values can be prepared by changing T, values The PEO block single crystals were melted and recrystallized at different. temperatures (T-rx) and the c-axis orientation of the recrystallized PEO crystals with respect. to glassy PS layers at different T, values can be monitored by Simultaneous 2D SAXS and WAXD techniques TWO observations of the PEO crystal orientation were found in these PS-b-PEO trials First. three different c-axis orientations of the PEO crystals with respect to the PS layer normal were observed random. homogeneous, and approximately homeotropic. Second a dramatic change from homogeneous to homeotropic takes place within a few degrees Celsius. The onset temperature or this orientation change (T-onset) decreases with increasing d(PEO) and sigma(PEO) values. The T-onset values were found to lie within a temperature range of nearly 20 degrees C (from 0 to - 19 degrees C) Mechanisms of the confined dimension and reduced tethering density effects oil determining those T-onset values at c proposed.