High-strength,high-pore-density Nanochannel Membrane Array For Osmotic Energy Conversion

The pore size and pore density of ion exchange membranes are important factors for osmotic energy conversion.However,due to the complicated and high-cost procedure of regulating the pore size and pore density,there still remain challenge for preparing aligned nanochannel membranes with controllable pore size and pore density.The block copolymer with the special structure can be applied to prepare ideal nanochannels through reasonable design and precise synthesis.In this thesis,a block copolymer for preparing nanochannel films is synthesized.The structure,molecular weight,and polydispersity of block copolymer are confirmed by hydrogen nuclear magnetic resonance spectroscopy,infrared spectroscopy,and gel permeation chromatography.The nanochannel films with different pore diameters and pore densities are prepared based on the obtained block copolymer.The successful preparation of nanochannel films with controllable pore size and pore density are verified through infrared spectroscopy,nanoindentation test,transmission electron microscope,and atomic force microscope.Since the inner wall of the prepared nanochannel contains sulfhydryl groups,which can be oxidized by H₂O₂ to form sulfhydryl anions,the high-efficiency conversion of salt difference energy can be explored through the ion transmission test.First,the block copolymers PEO-b-PChal containing disulfide bonds,chalcone group and coumarin styrene monomers,with different molecule weights,which can be photo crosslinked and cleaved by DTT(Dithiothreitol)reduction,are designed and synthesized by reversible addition-fragmentation chain transfer(RAFT)polymerization.The thermal stability of the block copolymers is investigated by TGA,and the result show that both polymers display excellent thermal stability.The results of DSC and polarized light microscopy present that this polymer shows liquid crystal behavior,which benefits the later self-assembly.Furthermore,the film of the block copolymer is irradiated by the 365nm ultraviolet light to test its crosslink ability and cleavability.With the increase of the irradiation time,the absorption intensity at the corresponding?-?*transition decrease,which indicate the degree of cross-linking is increasing.The block copolymer PEO_5k-b-PChal via self-assembly form a hexagonal-packed structure after the thermal annealing.The nanopores of the film is obtained by DTT reduction cleavability.The sulfhydryl groups in the pores are further oxidized by H₂O₂,making the nanopores possess anion selectivity.The nanoindentation test verifies its excellent mechanical properties.The hardness of the block copolymer increases by 3 times,and the elastic modulus increases by 2.6 times,after crosslinking.The results of TEM and AFM indicate the formation of nanopores in the ion exchange membrane.The current and voltage test shows that the ion exchange membrane containing sulfhydryl anions in the nanopores,which can selectively permeate cations.Further exploring its osmotic energy conversion performance in the corresponding electrochemical device,the maximum output power is 1.28W/m² at 500-fold concentration gradient.