Computer Simulations On The Gating Of Responsive Polymer Brush Modified Nanopores

The applications of intelligent nanopores in micro-flow control,material separation,antifouling and so on are very popular.In this thesis,the applications of various responsive nanopores and intelligent nanopores are reviewed.The mechanism of the switching effect of responsive polymer modified nanopores and the conditions for realizing the switching effect of nanopores were also studied by dissipative particle dynamics simulations.This provides a theoretical basis for the practical preparation of the switching effect of intelligent nanopores.Firstly,pH-responsive block copolymers(polyacrylic acid(PAA)-poly 2-vinyl pyridine(P2VP))were studied.Effects of different block sequences on the smart gating was studied.The results show that only the wall-PAA-P2 VP block sequence can form smart gates under different pH values.Grafting density and the chain length are important factors affecting the smart gating.Under proper grafting density and chain length of block polymers,different-sized smart membranes can be formed under different pH values;the smart gate can be switched from the “open” state to the “closed” state.Finally,the effect of block ratio on smart gating was also studied.Results show that the size of the block-copolymer-brush-grafted nanopore decreases gradually with the increase of PAA proportion and finally the “closed” states are almost formed.Secondly,the switching effect of nanopore modified by double-responsive block polymer was studied.The effect of different block sequences on the nanopore switching was studied.The results show that only the wall-PNIPAM-PAA block sequence can realize different switching effects of nanopores under different conditions.Meanwhile,the effects of grafting density,chain length and block ratio on the nanopore switching effect were also investigated.The results show that different nanopores can be realized at the moderate to high grafting density,the suitable chain length and the medium block ratio,which can be used to control the size of the switch.Finally,the smart gates of nanopores modified by zwitterionic polymer brush(Carboxylate betaine;PCBMA)were studied.The effects of pH and salt concentration on the smart gates of nanopores were discussed.The results showed that high grafting density and relatively long chain length could realize the switching effect of nanopore under different pH conditions.Under the condition of higher salt concentration,lower grafting density and shorter polymer chain length,the switch effect of nanopore could be realized.Under different salt concentrations,the size of nanopore varied differently.By comparing the effects of pH and salt concentration on the nanoscale switching effect,it was found that the effect of salt concentration on the smart gates was relatively stronger.The results of this thesis can provide some theoretical guidance for the design and construction of nanopores with antifouling properties.