Membranes based on polymer-grafted nanoparticles (PGNPs) have emerged as strong candidates for key gas separations due to their tunable permeability, selectivity, mechanical properties, and aging resistance. Here, we show the importance of keeping nanoparticles spatially well-dispersed through the whole process of grafting chains onto their surfaces─this is illustrated by measuring the gas-separation properties of PGNP membranes. Specifically, while we start with well-dispersed bare NPs in solution, this dispersion state is affected when we functionalize their surface with the polymer initiating agent, which then causes local NP agglomeration (i.e., effectively leading to a larger NP core, to which chains are grafted) and poor gas-separation performance relative to our previous results on PGNP membranes. Instead, when we cap the NPs with a protective layer that prevents NP agglomeration during surface functionalization, followed by grafted polymer synthesis, we obtain significantly higher gas permeabilities. While these results can be rationalized by the fact that the gas-permeation properties of smaller NPs grafted with polymer chains are better than those of larger NPs at the same effective grafting density and graft chain length, these results emphasize the important role of particle dispersion during all steps of the formation of PGNPs.

基于聚合物接枝纳米颗粒（PGNPs）的膜由于其可调的渗透性、选择性、机械性能和耐老化性，已成为关键气体分离过程中的强有力候选材料。在这里，我们展示了在整个将链接枝到纳米颗粒表面的过程中保持纳米颗粒空间良好分散的重要性——这一点通过测量PGNP膜的气体分离性能来说明。具体来说，在使用时我们将溶液中初始均匀分散的裸露NPs进行表面功能化处理以添加聚合物引发剂后，这一分散状态受到影响，导致局部NPs聚集（即有效形成了更大的NP核心，然后在此基础上接枝链），从而相对于我们之前关于PGNP膜的结果表现出较差的气体分离性能。相反，在对NPs进行表面功能化前用保护层封端，防止NPs在该过程中的聚集，并随后进行接枝聚合物合成，则可以获得显著更高的气体渗透性。虽然这些结果可以通过以下事实来解释：与较大NP相比，在相同有效接枝密度和接枝链长度下，较小的NP接枝聚合物链后的气体渗透性能更好，但它们强调了在PGNPs形成过程中所有步骤中颗粒分散的重要作用。