Effect Of Molecular Topology On The Self-assembly Behavior Of Giant Molecules

Amphiphilic block copolymers can form diverse microstructures by self-assembly in solution and bulk,which offers an effective"bottom-top"appproach to creat various order structures for diverse functions and properties.It has broad application prospects in the fields of biology,medicine,catalysis,and photoelectricity.Limited by the driving force of microphase separation(?N),traditional block copolymer self-assembly is difficult to form ordered structures with feature size below 10 nm.In recent years,through modular design and precise synthesis,a series of giant surfactants have been constructed using"nano-atoms"and polymers.Modifying a large number of functional groups on the nano-atoms,through the synergistic secondary bond effect,can significantly increase the driving force of micro-phase separation,resulting in a highly ordered structure of lower nano-size.Besides,it was found that the topology of giant surfactants has a decisive influence on its self-assembly behavior.Based on the above background,in this paper,in order to broaden the scope of the topological structure of giant surfactants,a series of single-chain nanoparticles(SCNPs)with different molecular weights and crosslinking densities were first synthesized.Then giant surfactants with linear tail or SCNPs tail were prepared by modular design and precise synthesis.The self-assembly behaviors in bulk and solution were studied,and the influence of tail chain topology on the self-assembly behavior of giant surfactants was analyzed.The specific research contents are as follows.(1)Synthesis of giant surfactants with linear tail or SCNPs tail.First,four kinds of SCNPs with different molecular weights and crosslinking densities were efficiently prepared by slow dropwise addition.Second,POSS with alkynyl group(VPOSS-alkyne)and SCNPs or linear polymer with azide group were synthesized.Third,through azide-alkyne click reaction,VPOSS-alkyne and SCNPs or linear polymer were connected.Finally,giant surfactants with SCNPs or linear tail were synthesized through thiol-ene click reaction.The products of each step were characterized by size exclusion chromatography(SEC),nuclear magnetic resonance hydrogen spectroscopy(~1H NMR),Fourier transform infrared spectroscopy(FT-IR),and differential scanning calorimetry(DSC).(2)Research on self-assembly of giant surfactants with different tail topologies in bulk.The synthesized giant surfactants were heat-treated under 120?.Then the self-assembly structure of the giant surfactants in bulk was studied by small-angle X-ray scattering(SAXS)technique and transmission electron microscope(TEM).Four kinds of giant surfactants with linear tail self-assembled into hexagonally packed cylinder(Hex)phase.Giant surfactants with SCNPs tail have lower order as a result of relatively rigid structure of the SCNPs.The feature size of the microphase separation structure of giant surfanctants with SCNPs tail is smaller than the feature size of corresponding linear topological isomer because the SCNPs has a volume shrinkage.(3)Research on self-assembly of giant surfactants with different tail topologies in solution.A pair of topological isomers of giant surfactants were used as the research object.The micelles were observed by transmission electron microscope(TEM).Giant surfactants with linear tail self-assembled into spherical micelles and vesicles as water content of the solvent changing.Due to the effect of SCNPs structure,giant surfactants self-assembled into lameller micelles and unconventional stuctures.