Membrane design for removal of environmental pollutant from waste water by plasma graft

我们制备了一种分子识别离子门膜。这种合成膜会对特定的溶剂化离子做出反应，自发地打开和关闭其毛孔。除了这种开关功能，我们发现这种膜可以控制其孔大小，以响应特定离子的已知浓度。以N-异丙基丙烯酰胺(N-异丙基丙烯酰胺)和苯并[18]冠-6-丙烯酰胺(BCAM)的共聚物填充多孔聚乙烯膜，采用等离子体接枝共聚法制备膜。众所周知，NIPAM有一个较低的临界溶液温度，在此温度下，其在水中的体积变化很大。BCAM的冠状受体捕获特定的离子，并导致LCST的移位。因此，选择性地响应K^或Ba^-lt；2&gt；，接枝共聚物在两个LC-ST之间的恒温下在孔内膨胀和收缩。与含有Ba^&lt；2&gt；的溶液相比，不含Ba^&lt；2&gt；的溶液通量降低了约两个数量级。通过过滤不同溶质大小的葡聚糖水溶液来估计孔大小。这表明，膜的孔径在5-27 nm之间变化，以响应Ba^&lt；2&gt；浓度的变化。对于Ca^&lt；2&gt；溶液，没有观察到这样的变化。此外，这种孔隙大小的变化在所有孔隙中都是均匀发生的，因为总是存在一个可以穿过孔隙的溶质大小的明确截止值。这种膜不仅可用作分子识别离子门，还可用作自发控制渗透通量和溶质大小的装置。此外，我们还可以根据受体的数目和logK以及接枝聚合物的*H和LCST信息来设计分子识别门膜，并且可以很容易地测量这些材料的特性。当我们想要制备一种新的受体的膜或改变反应条件时，我们不需要通过反复尝试来制备膜。

We have fabricated a molecular recognition ion gating membrane. This synthetic membrane spontaneously opens and closes its pores in response to specific solvated ions. In addition to this switching function, we found that this membrane could control its pore size in response to a known concentration of a specific ion. The membrane was prepared by plasma graft copolymerization, which filled the pores of porous polyethylene film with a copolymer of NIPAM (N-isopropylacrylamide) and BCAm (benzo[18]crown-6-acrylamide). NIPAM is well known to have an LCST (lower critical solution temperature), at which its volume changes dramatically in water. The crown receptor of the BCAm traps a specific ion, and causes a shift in the LCST. Therefore, selectively responding to either K^+ or Ba^<2+>, the grafted copolymer swelled and shrank in the pores at a constant temperature between two LCSTs. The solution flux in the absence of Ba^<2+> decreased by about two orders of magnitude over a solution flux containing Ba^<2+>. The pore size was estimated by the filtration of aqueous dextran solutions with various solute sizes. This revealed that the membrane changed its pore size between 5 and 27 nm in response to the Ba^<2+> concentration changes. No such change was observed for Ca^<2+> solutions. Furthermore, this pore size change occurred uniformly in all pores, as a clear cut-off value for a solute size that could pass through pores was always present. This membrane may be useful not only as a molecular recognition ion gate, but also as a device for spontaneously controlling the permeation flux and solute size. Also, we can design the molecular recognition gating membrane from information about number and logK of receptors and * H and LCST of grafted polymer, and we can measure these material characteristics easily. When we wish to prepare a membrane of a new receptor or change response conditions, we don't need to prepare membranes by try and error.