SEM研究PET核孔膜的光接枝聚合

SEM INVESTIGATION OF PHOTOGRAFTING POLYMERIZATION ON PET NUCLEOPORE MEMBRANES

以PET核孔膜为基材 ,二苯甲酮为引发剂 ,采用光接枝方法实现了丙烯酸和丙烯酰胺在核孔膜上的接枝 ,用扫描电镜 (SEM)直接观察了接枝前后膜的表面形貌 ,考察了不同因素对于接枝位置和接枝效果的影响 .发现膜材料本身特性和接枝反应条件对接枝位置和接枝效果有较大影响 .通过光接枝能够实现膜孔的封盖、缩小、填堵等不同的效果 .采用正侧涂布法反应 ,标准直孔 ,特别是小孔径膜 (0 4 μm) ,不利于孔内的接枝 ,接枝主要在膜的表面 ,从而产生孔封盖效应 .双锥形的非标准直孔 ,由于孔壁的受光性好 ,容易发生孔壁上的接枝从而被填充 .大孔径的膜 (5 μm) ,需要加入交联剂才能在孔壁上形成厚的接枝层 .提出了一种新的反应方法 背侧吸附法 ,反应液依靠毛细作用由膜的底部吸入膜孔 ,膜的向光侧表面不存在反应液 ,接枝只发生在膜孔内 ,从而得到很好的填孔效果 .

The photograft polymerization on porous substrate, poly ( ethylene terephthalate) ( PET) nucleopore membranes, was investigated by directly observing the configuration under SEM. The result of photografting strongly depends on the grafting methods and the nature of substrate membranes, such as pore size and pore shape, and different membrane configurations were obtained, for instance, decreasing pore size, pore-covering and pore-filling. To topside method, a standard straight pore shape is adverse to grafting inside pores, especially to small pore size membranes (0.4 mum), and it tends to give a pore-covering effect i.e. graft mainly occurs on the membrane surface rather than inside the membrane pores. The cone-shaped pores have much effective grafting area and are more easily filled than straight pores. To large pore size membrane (5 mum), crosslink agent is necessary to form a thick graft layer on the pore wall. A new backside adsorption method was applied in which the reaction solution was adsorbed into pores from the membrane backside owing to the capillarity and grafting polymerization was restricted inside pores. It is suitable for the synthesis of small pore diameter pore-filling membrane without changing the membrane surface characters, such as the photograft pore-filling modification of ultrafiltration membrane. Membrane pore size could be adjusted via selecting correct photografting technique and grafting degree (D-g). With the increase of grafting degree, the pore size and water flux of grafted membranes are decreased. The results of photograft polymerization on nucleopore membranes, a model of ideal membrane, provide valuable information for the photografting modification of other membranes.