Preparation of poly(ethylene glycol) aligned porous cryogels using a unidirectional freezing technique

Poly(ethylene glycol) (PEG) cryogels with aligned porous structures were prepared by unidirectional freezing and subsequently cryopolymerization. The aqueous reaction precursor of poly(ethylene glycol) diacrylate (PEGDA) and the initiator was first unidirectionally frozen using liquid nitrogen or other cooling agents such as frozen ethyl alcohol and frozen acetic ether, followed by radical polymerization at subzero temperature. The morphology of the obtained cryogels was observed by scanning electron microscopy (SEM) and confocal laser scanning microscope (CLSM). The pore structure of the obtained cryogels was the replica of the unidirectional ice crystals formed during the unidirectional freezing. Microtubular pores aligned along the freezing direction were observed in both dry and swollen states. The obtained cryogels showed anisotropic compressive strength according to the pore directions. The effect of the PEGDA molecular weight and the freezing temperature on morphology of the orientation-structured cryogels were also studied. The pore diameter could be adjusted from 10 to 50 mu m.