聚乙二醇、聚丙二醇和环氧乙烷-环氧丙烷嵌段共聚物在固液界面上的吸附——Ⅰ.活性炭/水界面

测定了25℃时活性炭自水溶液中吸附五种聚乙二醇(PEG)、一种聚丙二醇(PPG)和三种环氧乙烷(EO)-环氧丙烷(PO)嵌段共聚物的吸附等温线。结果表明,各等温线均为Langmuir型的,且在较低浓度时即可达极限吸附。当以g.g~(-1)表示吸附量时,各聚合物的极限吸附量相近。对于PEG系列和EO-PO嵌段共聚物系列,极限吸附时每个分子占据的面积与分子中所含EO数的关系为两条斜率相同的直线。由直线斜率和后一直线的截距可求得每个EO和PO所占的面积分别为26和2.9 nm~2。这些结果支持了分子以其EO和PO链节都平躺在表面上的吸附模型。

ADSORPTION OF POLYETHYLENE GLYCOLS,POLYPROPYLENE GLYCOL AND POLYOXYETHYLENE-POLYOXYPROPYLENE BLOCK COPOLYMERS ON SOLID/LIQUID INTERFACES Ⅰ .ACTIVE CARBON/WATER INTERFACE

The adsorption isotherms of polyethylene glycols(PEG,molecular weights of 400,1000, 3350, 6000 and 20000), one polypropylene glycol(PPG) and polyoxyethylene -polyoxypropylene block co-polymers (L61, L64, and F68) from water onto the active carbon have been measured (at 25℃).The results show that all the isotherms are Lagmuir-type, and the limiting, or plateau adsorption is approached at relatively low concentration The limiting adsorption(g.g-1) of the polymers onto active carbon is constant apparently. For PEG series, the plot of molecular area at limiting adsorption (A) versus the number of ethylene oxide units in the polymer molecules (n_(EO)) is a straight line through the origin. For EO-PO co-polymer series the A-n_(EO) plot is also a straight line with same slop as that for PEG series, however, the straight line intercepts with area axis. The areas of EO and PO calculated from the slop and the intercept are 2.6 nm~2 and 2.9 nm~2, respectively. From these results, it is suggested that the adsorbed molecules lies flat on the active carbon surface.