Crystallizable diluent-templated polyacrylonitrile foams for macroporous carbon monoliths

Polyacrylonitrile (PAN) foams with different pore structures were prepared for the fabrication of macroporous carbon monoliths. The foams were prepared through thermally induced phase separation (TIPS) method using dimethyl sulfone (DMSO2) as a crystallizable diluent. Honeycomb-like porous foam is obtained from PAN/DMSO2 mixture containing about 5 wt.% PAN, and those with channel-like pores are resulted from the mixtures with 10–40 wt.% PAN. However, they only have few mesopores and the porosity is as low as 30–47% for the foams prepared from those mixtures containing 50–60 wt.% PAN. Real-time observation with polarized optical microscopy reveals that the channel-like structure stems from the spherulitic orientation of DMSO2 crystals in the polymer matrix. Taking into account this morphology, DMSO2 crystals are capable of acting as in situ formed templates, which subsequently enable to shape the final pore structure of PAN foams. Macroporous carbon monoliths with honeycomb- or channel-like pores were constructed from PAN foams by oxidative stabilization and carbonization. Their graphitic structure and specific surface areas were analyzed by wide-angle X-ray diffraction and Brunauer–Emmett–Teller measurement. This TIPS method using crystallizable diluent provides a new route to control the porous structure of PAN foams for carbon materials.