On Defining a Simple Empirical Relationship to Predict the Pore Size of Mesoporous Silicas Prepared from PEO-b-PS Diblock Copolymers
On Defining a Simple Empirical Relationship to Predict the Pore Size of Mesoporous Silicas Prepared from PEO-b-PS Diblock Copolymers
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DOI：
10.1021/cm801978w
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发表时间：
2009-01-13
影响因子：
8.6
通讯作者：
Hornebecq, Virginie
中科院分区：
文献类型：
--
作者：
Bloch, Emily;Llewellyn, Philip L.;Hornebecq, Virginie
以自制的聚氧化乙烯-b-聚苯乙烯（PEO-b-PS）共聚物为模板剂，成功地合成了具有大孔道的介孔二氧化硅。采用活性/可控自由基聚合法合成了PEO-b-PS共聚物。的多孔结构（中孔尺寸，尺寸分布，和微孔体积），其特征在于使用小角X射线散射，电子透射显微镜，和氮吸附测量。在这项研究中，我们已经调查了两个系列的PEO-b-PS共聚物与一个恒定的聚合度的PEO嵌段为每个系列（N-PEO = 114和N-PEO = 232）的PS和PEO嵌段长度的中孔性的依赖性。结果表明，随着PS嵌段长度（N-PS）的增加，中孔尺寸增大，微孔体积减小。PEO嵌段参与了微孔和中孔的形成。通过对实验数据的拟合，得到了PS嵌段（N-PS）和PEO嵌段（N-PEO）长度与孔半径的简单经验关系式：R-P（nm）= 0.36。（NPEONPS0.5）-N-0.19。这种关系对于低分子量和高分子量共聚物都是一致的，并且当使用PEO-b-PS共聚物作为模板时，可以容易地用于在大范围（从4至22 nm）内微调二氧化硅材料的中孔尺寸。此外，还研究了合成温度（在25 ° C和60 ° C之间）对多孔结构的影响，并且发现通过增加合成温度，中孔直径保持相对恒定;然而，孔入口的尺寸增加，导致更开放的孔结构。
Mesoporous silicas with large and accessible pores have been successfully synthesized using laboratory-made poly(ethylene oxide)-b-polystyrene (PEO-b-PS) copolymers as templates. The PEO-b-PS copolymers were synthesized using living/controlled radical polymerization. The porous structure (mesopore size, size distribution, and microporous volume) was characterized using small-angle X-ray scattering, electron transmission microscopy, and nitrogen sorption measurements. In this study, we have investigated the dependence of the mesoporosity on both the PS and PEO blocks length using two series of PEO-b-PS copolymers with a constant degree of polymerization of the PEO block for each series (N-PEO = 114 and N-PEO = 232). It was found that the mesopore size increases and the microporous volume decreases as the PS block length (N-PS) increases. The PEO block participates to both the micropore and mesopore formation. By fitting these experimental data, a simple empirical relationship between the pore radius and the length of the both PS block (N-PS) and PEO block (N-PEO) is found R-P (nm) = 0.36.(NPEONPS0.5)-N-0.19. This relationship is in agreement for both low- and high-molecular-weight copolymers and can be easily be used to fine-tune the mesopore size of silica materials, in a large range (from 4 to 22 nm), when using PEO-b-PS copolymers as templates. Furthermore, the influence of the synthesis temperature (between 25 and 60 degrees C) on the porous structure was also investigated and it was found that by increasing the synthesis temperature, the mesopore diameters remain relatively constant; however, the pore entrances increase in size, leading to more open pore structures.