Abstract In this work, a concept of hierarchically porous membranes (HPMs) with isolated-round-pores connected by narrow-nanopores whose separation performance could be enhanced significantly is reported. On one hand, the simulation results provide the direct evidence that the existence of isolated-round-pores can shorten diffusion length and minimize diffusion barrier, which is the reason for the higher flux relative to the reference with only narrow-nanopores; on the other hand, HPMs have been fabricated successfully in ternary blend of PVDF/PMMA/PLLA. Due to the special miscibility in the blend, phase separation produces PLLA islands and PVDF/PMMA matrix. In the matrix, PMMA has been expelled out during the crystallization of PVDF, resulting in bi-continuous structures of them in nanometers. After the extraction with chloroform, the narrow-nanopores (from nano-continuous PMMA) connect the isolated-round-pores (from islands of PLLA) with each other, yielding interpenetrated micro-channels. During separation with HPMs, the selectivity is determined by porous structures in matrix. It has been further improved by the width of the anisotropic narrow pores, contributing to the high rejection ratio. The permeability has been enhanced remarkably via shorter diffusion length and lower diffusion barrier resulted from the isolated-round-pores. Our result provides a novel solution for trade-off effect between permeability and selectivity in separation.

中文翻译：

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具有由窄纳米孔连接的孤立圆形孔的分级多孔膜：分离中权衡效应的新解决方案

摘要 在这项工作中，报告了一种分层多孔膜 (HPM) 的概念，该膜具有由窄纳米孔连接的孤立圆形孔，其分离性能可以显着提高。一方面，模拟结果提供了直接证据，即孤立圆形孔的存在可以缩短扩散长度并使扩散势垒最小化，这是相对于仅具有窄纳米孔的参考具有更高通量的原因；另一方面，在 PVDF/PMMA/PLLA 的三元混合物中成功制造了 HPM。由于混合物中的特殊混溶性，相分离会产生 PLLA 岛和 PVDF/PMMA 基质。在基体中，PMMA 在 PVDF 结晶过程中被排出，导致它们在纳米级的双连续结构。用氯仿萃取后，窄纳米孔（来自纳米连续 PMMA）将孤立的圆形孔（来自 PLLA 岛）相互连接，产生相互渗透的微通道。在使用 HPM 进行分离时，选择性由基质中的多孔结构决定。各向异性窄孔的宽度进一步改善了它，有助于提高截留率。由于孤立的圆孔导致更短的扩散长度和更低的扩散屏障，渗透率显着提高。我们的结果为分离中渗透率和选择性之间的权衡效应提供了一种新的解决方案。选择性由基质中的多孔结构决定。各向异性窄孔的宽度进一步改善了它，有助于提高截留率。由于孤立的圆孔导致更短的扩散长度和更低的扩散屏障，渗透率显着提高。我们的结果为分离中渗透率和选择性之间的权衡效应提供了一种新的解决方案。选择性由基质中的多孔结构决定。各向异性窄孔的宽度进一步改善了它，有助于提高截留率。由于孤立的圆孔导致更短的扩散长度和更低的扩散屏障，渗透率显着提高。我们的结果为分离中渗透率和选择性之间的权衡效应提供了一种新的解决方案。