Translocation of polymer chains through nanopores (ultrafiltration behavior) is not only a basic problem in polymer physics and biophysics

but also related to many physical and chemical processes

such as gene transfection

protein transportation

and separation of polymer chains by size exclusion chromatography. However

due to the lack of appropriate polymer model samples as well as ideal elongational flow fields

the ultrafiltration behavior of polymer chains has not been systematically explored experimentally for a long time. To deeply understand the ultrafiltration behavior of polymer chains and verify relevant theory

we have made much effort on this subject in the past decade. In this article

we'll first review the classic theory of polymer chains passing through nanopores

and then provide an overview of our recent theoretical and experimental research achievements in this field

more specifically

we have (1) successfully observed the coil-to-stretch first-order transition of polymer linear chain passing through nanopores

and found that the critical flow rate (qc) is indeed independent on the chain length

but dependent on the pore size

inconsistent with de Gennes' prediction; (2) developed a unified theoretical description of polymer chains with different topologies passing through a nanopore; (3) systematically studied the effects of polymer chain topology and pore structure on the ultrafiltration behavior of polymer chains; and (4) successfully applied the ultrafiltration method into the separation of polymer chain mixtures and the rapid transition between various polymeric aggregated structures.