Coaxial ring-layered poly(N-isopropylacrylamide) gel columns of improved thermoresponses

To improve responsive speed of gel columns, some structures and methods have been pursued and designed. Normal gel columns are often obtained under motionless state. For investigating effect of rotation on preparation and thermally-responsive characteristic of gel columns, an axial rotation apparatus was designed to prepare poly(N-isopropylacrylamide) (PNIPAM) columns at different speed in this work. Some technologies such as SEM, the optical coherence tomography, swelling-deswelling measurements and dismembering technology were applied to character structural morphology and the thermoresponsive speed. When the rotating speed was less than 100 rpm, a novel structure of PNIPAM columns has been successfully obtained. From the cross-sectional view, the columns had a coaxial-ring-layered structure. Compared with the normal PNIPAM column prepared under motionless condition, the novel PNIPAM columns showed more quick swelling-deswelling or reswelling speed response to temperature owing to the axial-ring-layered structure. For the novel structure of PNIPAM columns, the intense between the ring-layered structures increased with increasing crosslinker dosage. By dismembering the proposed column, all layers in the novel structure were not alone and had interrelation each other. The arrangement about structured networks along the axial direction was better than that along the circle direction. Therefore water in the proposed columns flowed mainly along the axial direction. The results may lead to technological application on oily water separation to prepare highly-functional materials with ordered microstructure.