From Microphase Separation to Self-Organized Mesoporous Phenolic Resin through Competitive Hydrogen Bonding with Double-Crystalline Diblock Copolymers of Poly(ethylene oxide-b-ε-caprolactone)

Abstract

A series of immiscible crystalline–crystalline diblock copolymers, poly(ethylene oxide)-b-(ε-caprolactone) (PEO-b-PCL), were synthesized through ring-opening polymerization and then blended with phenolic resin. FT-IR analyses demonstrate that the ether group of PEO is a stronger hydrogen-bond acceptor with the hydroxyl group of phenolic resin than is the carbonyl group of PCL. Phenolic, after being cured with hexamethylenetetramine (HMTA), results in the excluded and confined PCL phase based on analyses by differential scanning calorimetry (DSC). This effect leads to the formation of a variety of composition-dependent nanostructures, including disorder, gyroid and short-cylinder structures. The self-organized mesoporous phenolic resin was found only at 40–60 wt % phenolic content by an intriguing balance of the contents of phenolic, PEO, and PCL. In addition, the mesoporous structure was destroyed at higher PCL/PEO ratios in the block copolymers, as determined by small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) experiments. In addition, the large and long-range order of bicontinuous gyroid-type mesoporous carbon was obtained from mesoporous gyroid phenolic resin calcined at 800 °C under nitrogen.