Dynamics Of Polymer Translocation Into And Out Ot Confinements Througt Nanopores

As a biological phenomenon in nature, polymer translocation into and out of a confinement through a nanopore is a complex process. The dynamics of polymer translocation are significantly affected by the conformational entropy and bending energy of chain and the non-equilibrium of translocation. In-depth analysis of the translocation dynamics mechanism, enriching our understanding of life, is one of the key problems in polymer science. Based on scaling theory and blob theory, we investigate the dynamics of flexible and semiflexible polymer translocation into and out of a confinement through a nanopore in2D and3D by using Langevin dynamics simulation.First, we investigate the dynamics of polymer translocation into a circular nanocontainer through a nanopore under a driving force F in2D and3D. We observe that the translocation probability Ptrans initially increases and then saturates with increasing F, independent of φ, which is the average density of the whole chain in the nanocontainer. We observe pauses during the translocation process. With increasing the φ, the frequency and time of pauses increase. Either in2D or in3D, the translocation time distribution undergoes a transition from a Gaussian distribution under small φ and strong driving force F to an asymmetric distribution under large φ. The factors such as φ the length of chain N and the driving force F have remarkable effects on the translocation time τ. Meanwhile, we find a nonuniversal scaling exponent of the translocation time τ as chain length N, τ～Nα, depending on φ and F. Moreover, we observe τ～φ1+1/(3v3-1)～φ2.25(ν3=0.588) during the translocation in3D. The translocation time τ decreases with increasing the driving force F. These results are interpreted by the conformation of the translocated chain in the nanocontainer and the time of an individual segment passing through the pore during translocation. Moreover, the translocation of polymer through ananopore is a non-equilibrium process.Second, we investigate the dynamics of polymer translocation into a confined space under a driving force through a nanopore, with particular emphasis on the chain stiffness and the shape of the confinement by using Langevin dynamics simulations in2D. Compared with an isotropic confinement (sphere), an anisotropic confinement (ellipsoid) with the same volume slows down the translocation, and the translocation time τ increases with increasing the aspect ratio of the ellipsoid for flexible chain. We further find that it takes different lengths of time for polymer translocation into the same ellipsoid through the major axis and minor axis directions, depending on the average density of the whole chain in the ellipsoid,φ. For φ lower than a critical value φc, the translocation through the minor axis is faster, and vice versa. For semiflexible chain, we observe that with increasing the chain stiffness κ, the translocation time τ always increases for different shapes of confinements. For an ellipse, τ is different for the translocation through its minor and major axis directions. Under the weak confinement, the translocation through the minor axis direction is faster than that through the major axis direction for different κ while this is true only for high κ under strong confinement. Particularly, for both weak and strong confinements we find that packaging into an ellipse through its minor axis direction is faster than that for a circle of the same area for high κ.Finally, we investigate the dynamics of polymer translocation out of a spherical nanocontainer through a nanopore. We observe that the translocation probability Ptrans initially increases and then approaches1with increasing the volume fraction φ. The translocation time τejection distributions accord with different asymmetric long-tail distribution with increasing φ. Moreover, we find that τejection increases with increasing the chain length N, and decreases with increasing φ. More importantly, we find τ～N1.50φ-1.06. In addition, we investigate the effect of the chain stiffness on the translocation probability, translocation time and its distribution. With increasing the chain stiffness, the translocation probability Ptrans decreases, the translocation time τejection increases, and its distribution has a long-tail.