Preparation And Applications Of Living Supramolecular Assembly For Simple Monomers By Confinement Effect Of Layered Double Hydroxides

Recently,the research of living supramolecular assembly（LSA）and its application in biomimetic materials are becoming more and more popular due to that it is far from thermodynamic equilibrium.However,this emerging field still faces many challenges in simplify LSA monomer,control over living ability of LSA and practical application.Layered double hydroxide material（also known as hydrotalcite,LDH）can provide a two-dimensional topological confinement space,which is good at making anisotropic materials.The long-range ordered arrangement obtained from LDH confinement is hardly possible for dissociative monomers to access in the thermodynamic equilibrium solution.In this paper,a new kind of confinement assisted LSA method is proposed,which has good universality in monomers with simple structure.The mostly research contents in this paper are as follows:1.We propose a kind of LDH confinement assisted method to prepare LSA.In this work,solvent green 7（SG7）is chosen as a model molecule due to the excellent fluorescence performance.According to a set of spectroscopic test,we studied the anisotropy and stacking mode of long-range SG7 array between LDH layers.Based on the fluorescence difference of different SG7aggregates,the formation process of LSA can be monitored.Based on Density Functional Theory,the potential energy surface of SG7 array with the orientation at 0～90°can be obtained,from which SG7 molecules overcome a huge energy barrier of 70.55 k J/mol to achieve oriented long-range SG7 array assisted by confinement effect of LDH.Moreover,the experimental results proves that the formation pathway of LSA is dependent on preparation method,instead of the final experimental parameters.Thus,LSA is metastable.The size control over LSA can be proved by its increase as the increase of concentration of input materials.The living property can be proved by that the size of seed-induced supramolecular assembly（SSA）increase in cycle experiment.The size control over SSA can also be proved by its increase as the increase of cycle index and concentration.Finally,another monomer candidates are chosen to prepare corresponding LSA and SSA products.By analysis of their living ability,it can be concluded that simple molecules with≥2 functional groups can be considered as possible monomer candidates in this kind of LSA method.Thus,this method not only simplify LSA monomer design,but also has good universality,which will greatly reduce the future cost of LSA applied in industry.2.The control over living ability of LSA and its application in chiral recognition can be realized by changing LDH size.Firstly,the important role of LDH confinement space can be proved by the comparison of living property of intercalated SG7-LDH and LDH with adsorbed SG7 on surface.Four kinds of LDH with the size of 20 nm,50 nm,100 nm and 3μm are prepared to produce corresponding living supramonomer（LSM）and LSA.In SEM images,the size of LSM and starting size of LSA show the increase with the increase of LDH size.However,the living ability of LSA decrease with the increase of LDH size according to cycle experiments.Thus,the final size of elongated LSA is affected by both the initial size and living activity of LSA.The real-time fluorescence intensity can monitor the formation process of four kinds of LSA,which indicate the kinetics of its formation.Based on this,it can be concluded that the kinetics of LSA becomes slower as the LDH size becomes smaller.Due to the different spatial structure of chiral arginine,the lag time of coassembly of LSM with L-arginine or D-arginine is different from each other.In this work,LSM made from 3μm SG7-LDH can extremely amplify the difference of lag time in coassembly,resulting in good chiral recognition.In all,the LSM with slow kinetics can be applied in chiral recognition while LSM with quick kinetics can be applied in preparation of coassembly.Thus,the control over living ability of LSA can be helpful to prepare LSA with suitable kinetics according to industry needs,which will broaden the prospect of LSA in practical application.3.With the advantages of LDH confinement and structural imprinting,achiral molecules can be induced to form chiral supramolecular assembly（CSA）.In this work,2,5-diaminobenzenesulfonic acid（DABSA）is chosen as a model molecule.The suitable solvent system for DABSA LSA has been studied.In detail,good solvent system is not fit for LSA while the addition of poor solvent with a certain ratio can prepare DABSA LSA and has good living property in cycle experiments.The chiral signal can both be observed in the above two kinds of solvent system,attributing to the amplification effect of LDH in asymmetry from different location of functional groups in DABSA.The molecular inherent asymmetry is transferred to DABSA array,resulting in its spatial asymmetry.Based on the theoretical results,DABSA molecules were arranged in the mode of bilayer between LDH layers.The two kinds of DABSA arrays have different inclined angle between LDH layers.After removal of LDH templates,the released DABSA arrays can be maintained for a while and then interacted to form living units with non-centrosymmetric structure.Thus,their left-handed and right-handed stacking are not enantiotropic,leading to different energy.This can induce the formation of CSA.In good solvent system,the formation pathway of CSA is complicated due to the occurrence and disassembly of LSA.In the poor solvent system,the existence of LSA amplifies the energy difference between different chiral stacking.Thus,the obtained CSA can be considered as single-handed.Compared with previous reports,DABSA is the simplest achiral monomer.The chirality of CSA can be amplified to a significant level in solution(|g _CD|=5×10^-3).Not only that,the metastable system of LSA is similar to biological systems,which may be a wonderful choice in supramolecular chemistry to investigate the origin of biological homochirality.The LDH confinement effect make us reminiscent of the confinement effect of living cells,which may be the source of symmetry breaking.It is anticipated to a significant progress in the explanation of the origin of biological homochirality.