Fabrication of Nanoporous Structures in Block Copolymer Using Selective Solvent Assisted with Compressed Carbon Dioxide
Fabrication of Nanoporous Structures in Block Copolymer Using Selective Solvent Assisted with Compressed Carbon Dioxide
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DOI：
10.1021/ma900123e
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发表时间：
2009-04
期刊：
影响因子：
5.5
通讯作者：
Rui Zhang;Hideaki Yokoyama
中科院分区：
文献类型：
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作者：
Rui Zhang;Hideaki Yokoyama
纳米结构薄膜的制造在多种应用中是重要的。介绍了一种在嵌段共聚物薄膜中引入纳米孔的制备方法。作为该方法的模型，聚（苯乙烯-b-2-乙烯基吡啶）（PS-PVP）薄膜的原始厚度约为150 nm的甲醇和CO2的混合物中使用。单独使用甲醇和二氧化碳都不能在PS-PVP薄膜中引入纳米孔;但甲醇和二氧化碳的混合物可以有效地将甲醇定位到PVP结构域中，并在去除后留下纳米孔。单独的甲醇对PVP嵌段具有很强的亲和力，并可能使PVP结构域溶胀，但玻璃状PS基质阻止它们溶胀。因此，通过CO2增塑降低PS的玻璃化转变温度（Tg）是成功引入纳米孔的关键。压缩的CO2降低了PS的Tg，可以在减压时从混合物中快速去除，并增加PS的Tg以防止纳米孔塌陷。纳米孔的尺寸可以通过改变CO2的压力成功地调节。在我们的实验时间尺度上，形态是不平衡的，并且所得的纳米多孔结构取决于该过程之前的初始形态。
The fabrication of nanostructured thin films is important in a variety of applications. This article presents a fabrication method for introducing nanoscopic pores into polymeric thin films of block copolymers. As a model of this method, poly(styrene-b-2-vinylpyridine) (PS-PVP) thin film of which the original thickness is about 150 nm was employed with mixtures of methanol and CO 2 . Neither methanol nor CO 2 alone can introduce nanopores into the PS-PVP thin films; however, the mixtures of methanol and CO 2 can effectively localize methanol into PVP domains and leave nanopores after being removed. Methanol alone has a strong affinity for PVP blocks and potentially swells the PVP domains, but the glassy PS matrix prevents them from swelling. Therefore, it is essential for the successful introduction of nanopores to reduce the glass-transition temperature (T g ) of PS by plasticizing with CO 2 . Compressed CO 2 , which reduces the T g of PS, can quickly be removed from the mixture upon depressurization and increases the T g of PS to prevent nanopores from collapsing. The size of the nanopores can be successfully adjusted by changing the pressure of CO 2 . On our experimental time scale, the morphologies were not equilibrium, and the resultant nanoporous structures depend on the initial morphologies before the process.