Highly ordered mesoporous resol-type phenolic resin and the corresponding mesoporous carbon materials were synthesized by using poly(ethylene oxide-b-caprolactone) (PEO-b-PCL) diblock copolymer as a soft template. The self-assembled mesoporous phenolic resin was found to form only in a specific resol concentration range of 40-70 wt % due to an intriguing balance of hydrogen-bonding interactions in the resol/PEO-b-PCL mixtures. Furthermore, morphological transitions of the mesostructures from disordered to gyroid to cylindrical and finally to disordered micelle structure were observed with increasing resol concentration. By calcination under nitrogen atmosphere at 800 °C, the bicontinuous mesostructured gyroid phenolic resin could be converted to mesoporous carbon with large pore size without collapse of the original mesostructure. Furthermore, post-treatment of the mesoporous gyroid phenolic resin with melamine gave rise to N-doped mesoporous carbon with unique electronic properties for realizing high CO adsorption capacity (6.72 mmol g at 0 °C).

In this study, in situ small‐angle X‐ray scattering (SAXS), in situ Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM) are used to monitor the formation of ordered mesophases in cured mixtures of phenolic resin and the diblock copolymer poly(ethylene oxide‐block‐ε‐caprolactone) (PEO‐b‐PCL). SAXS and TEM analyses reveal that the mesophase of the phenolic/PEO‐b‐PCL mixture transforms sequentially from disordered to short‐range‐ordered to hexagonal‐cylindrical to gyroidal during the curing process when using hexamethylenetetramine (HMTA) as a cross‐linking agent, indicating that a mechanism involving reaction‐induced microphase separation controls the self‐assembly of the phenolic resin. In situ SAXS is also used to observe the fabrication of mesoporous phenolic resins during subsequent calcination processes.

No abstract

A series of immiscible triple crystalline triblock copolymers, poly(ethylene oxide-b-ε-caprolactone-b-L-lactide) (PEO-b-PCL-b-PLLA), synthesized through sequential ring-opening polymerization, have been blended with phenolic resin. FTIR spectra revealed that the ether groups of the PEO blocks were stronger hydrogen bond acceptors for the OH groups of phenolic resin than were the CO groups of the PCL and PLLA blocks. Curing of phenolic with the templates and hexamethylenetetramine resulted in excluded and confined PCL or PLLA phases, depending on the phenolic content. This effect led to the formation of various composition-dependent nanostructures, including disordered structures, bicontinuous gyroids, hexagonally packed cylinders, and spherical micelle structures. Small-angle X-ray scattering and transmission electron microscopy revealed that self-organized mesoporous phenolic resin formed at phenolic contents of only 30−50 wt % as a result of an intriguing balance among the contents of phenolic and the PEO, PCL, and PLLA blocks. An interesting closed-loop mesoporous structure existed in the phase diagram of the mesoporous phenolic resins templated by the PEO-b-PCL-b-PLLA triblock copolymers.

After blending the triblock copolymer, poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (PEO-b-PPO-b-PEO) with novolac-type phenolic resin, Fourier transform infrared spectroscopy revealed that the ether groups of the PEO block were stronger hydrogen bond acceptors for the OH groups of phenolic resin than were the ether groups of the PPO block. Thermal curing with hexamethylenetetramine as the curing agent resulted in the triblock copolymer being incorporated into the phenolic resin, forming a nanostructure through a mechanism involving reaction-induced microphase separation. Mild pyrolysis conditions led to the removal of the PEO-b-PPO-b-PEO triblock copolymer and formation of mesoporous phenolic resin. This approach provided a variety of composition-dependent nanostructures, including disordered wormlike, body-centered-cubic spherical and disorder micelles. The regular mesoporous novolac-type phenolic resin was formed only at a phenolic content of 40–60 wt %, the result of an intriguing balance of hydrogen bonding interactions among the phenolic resin and the PEO and PPO segments of the triblock copolymer.