Interactive Mechanism Of Macroscopic Supramolecular Assembly

As a recent progress of supramolecular chemistry,macroscopic supramolecular assembly(MSA)has established a novel methodology to fabricate supramolecular materials through directly using building blocks with a size large than 10 micrometer,thus providing strong connections between fundamental research of supramolecular science and applied research of supramolecular materials.Originated from molecular assembly,MSA is also established based on non-covalent interactions;however,the mechanism underlying the interactive events between macroscopic interfaces is much more complex than those between molecular building blocks.As a result,precise and controllable assembly dramatically arises as a challenge.Especially,variables such as surface roughness of building blocks,density and motility of interface moieties,are influential in MSA.Currently most reports regarding MSA only describes the assembly phenomena while the underlying the MSA mechanism has been rarely studied.Therefore,this thesis aims at the interpretation of the assembly mechanism and mainly tackles two fundamental problems of "what kind of building blocks are applicable to MSA" and "how to achieve precise MSA".Here we have established a general design principle of building blocks that a highly flowable surface is requisite to realize MSA;meanwhile for the first time we have proposed a self-correction strategy based on dynamic assembly-disassembly to handle the problem of self-assembly being insensitive to errors and realized parallel,massive and precise MSA.The main conclusions are drawn as follows:1.We have proposed and verified that a highly flowable surface is requisite to realize MSA.To tackle the problem of "what kind of building blocks are applicable to MSA",we designed and fabricated model hydrogel systems with varied elastic modulus by considering the influence of the substrate deformability on the multivalent process in MSA.Meanwhile,other variables such as surface chemistry are kept constant by using a surface modification method of layer-by-layer assembled technique to introduce interactive moieties of cyclodextrin and azobenzene on the hydrogel surfaces.By correlating the MSA probability and the building block elasticity,we found a critical elastic modulus of 2.5 MPa to determine the realization of MSA,namely building blocks with a modulus below 2.5 MPa can achieve selective MSA while those above this value lead to no assembly.Based on these results,we have further elaborated the design principle of a highly flowable surface being requisite to realize MSA.2.We have proposed and verified that polyelectrolyte multilayers capable of self-healing can function as the flexible spacing coating.Based on our previous study that a flexible spacing coating can realize MSA of building blocks with high modulus,here we address the problem of "what kind of coating can be used as flexible spacing coatings".Taking PEI/PAA polyelectrolyte multilayers with several crosslinking density as model system,we found that only those with a low crosslinking density and high flowability,in other words,being capable of self-healing,can lead to MSA of building blocks with high modulus.Therefore,we propose that polyelectrolyte multilayers capable of self-healing can function as the flexible spacing coating,thus providing guidance to select flexible spacing coating.Moreover,we have extended the flexible spacing coating to some other self-healing systems and thus further supported this perspective.3.We have proposed a self-correction strategy based on dynamic assembly-disassembly processes.To tackle the problem of "how to achieve precise MSA",we designed and fabricated oppositely charged hydrogel building blocks as a model system.To automatically distinguish the precisely or poorly assembled hydrogel dimers by electrostatic interactions,we took advantage of the difference of diffusion kinetics of NaCl solutions to the assembled interfaces;thus the poorly assembled dimers can be selectively disassembled while the precise assemblies still remain.With alternate disassembly and assembly,we can achieve self-correction to realize precise MSA of 100 dimers simultaneously.Moreover,with other ratios of interactive hydrogels to form advanced structures,this self-correction mechanism can self-sort“structural isomers" in MSA.