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

我们研制了一种分子识别离子门控膜。这种合成膜响应于特定的溶剂化离子自发地打开和关闭其孔。除了这种开关功能，我们发现这种膜可以控制其孔径，以响应特定离子的已知浓度。采用等离子体接枝共聚法，将N-异丙基丙烯酰胺（NIPAM）和苯并[18]冠-6-丙烯酰胺（BCAm）的共聚物填充到聚乙烯多孔膜的微孔中，制备了聚乙烯微孔膜。众所周知，NIPAM具有LCST（低临界溶解温度），在该温度下，其体积在水中急剧变化。BCAm的冠受体捕获特定离子，并导致LCST的偏移。因此，在两个LCST之间的恒温下，接枝共聚物选择性地响应K^+或Ba^<2+>，在孔中溶胀和收缩。不含Ba^<2+>的溶液通量比含Ba^<2+>的溶液通量降低了约两个数量级。通过过滤具有各种溶质尺寸的葡聚糖水溶液来估计孔径。这表明，膜的孔径随着Ba^2+浓度的变化而在5 ~ 27 nm之间变化。而在Ca^2+溶液中则没有观察到这种变化。此外，这种孔径变化均匀地发生在所有孔中，因为始终存在可以通过孔的溶质尺寸的明确截止值。这种膜不仅可以用作分子识别离子门，而且可以用作自发控制渗透通量和溶质尺寸的装置。此外，我们还可以根据受体的数量和logK以及接枝聚合物的 * H和LCST信息设计分子识别门控膜，并且可以容易地测量这些材料特性。当我们想要制备一个新受体的膜或改变反应条件时，我们不需要通过尝试和错误来制备膜。

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.