Effect of crystallization of the polyhedral oligomeric silsesquioxane block on self-assembly in hybrid organic-inorganic block copolymers with salt

Abstract

We present a DSC and X-ray scattering study investigating the effect of polyhedral oligomeric silsesquioxane (POSS) block crystallinity on the self-assembly of a poly(acryloisobutyl polyhedral oligomeric silsesquioxane)-b-poly(ethylene oxide)-b-poly(acryloisobutyl polyhedral oligomeric silsesquioxane) (POSS-PEO-POSS) triblock copolymer and poly(ethylene oxide)-b- poly(acryloisobutyl polyhedral oligomeric silsesquioxane) (PEO-POSS) diblock copolymers mixed with lithium bis(trifluoromethanesulfonyl)imide salt. The POSS block in all copolymer/salt mixture organizes into a rhombohedral crystal, similar to that of the POSS homopolymer. Semicrystalline polymer/salt mixtures favor morphologies with flat interfaces (i.e., lamellae) despite the asymmetric nature of the copolymers; PEO/salt volume fractions range from 0 to 0.85. Coexisting lamellae and hexagonally packed cylinders as well as coexisting lamellae with different domain spacings are seen in many copolymer/salt mixtures wherein the POSS block is amorphous. Morphological phase transitions in these systems are seen in the vicinity of the POSS crystallization temperature.

Keywords

• Block copolymers
• Hybrid
• Electrolytes
• Phase behavior
• Phase separation
• Phase transition