Self-assembly Of Inorganic Nanoparticles And/or Macromolecules Driven By Host-Guest Inclusion Complexation

Our research group succeeded in developing new 'block copolymer-free strategies' to construct polymeric micelles from homopolymers or random copolymers etc.driven by hydrogen bonding.A series of "non-covalently connected micelles"(NCCM) in which the core and the shell are connected by hydrogen bonds were made by this strategy.In recent years,the host-guest interactions between Cyclodextrins(CD) and specific guest molecules have also been used as driving force to construct NCCM.Based on these progresses in self-assembly of macromolecules, this thesis is focused on using the host-guest interactions as driving forces to self-assemble metal and inorganic nanoparticles or macromolecules.The thesis is consisted of 5 parts:1.Reversible aggregation of gold nanoparticlesWe synthesized water-soluble gold nanoparticles(β-CD-AuNPs) which are modified byβ-CDs on the surfaces.And a ditopic guest(Di-Azo) with functional azobenzene groups at the two ends was also synthesized.β-CD-AuNPs tend to aggregate together upon addition of Di-Azo due to the host-guest inclusion complexation betweenβ-CD and Di-Azo.Further disassociation of the gold aggregates can be realized by addition of excess competitive hostα-CD which favors forming inclusion complexes with the guest more thanβ-CD does.The aggregation-disassociation ofβ-CD-AuNPs is confirmed to be reversible.2.Formation of Au/SiO₂ and Polymer/Au/SiO₂ trilayer complex nanoparticlesIn this part,we developed two new methods to obtain Au/SiO₂ complex nanoparticles:(1) SiO₂ nanoparticles with guest azobenzene groups on the surfaces (Silica-Guest) were synthesized.β-CD-AuNP and Silica-Guest were used as building blocks to construct Au/SiO₂ complex nanoparticles driven by the inclusion complexation betweenβ-CD and azobenzene groups.As a result,β-CD-AuNP self-assembles around the surface of SiO₂ forming "raspberry-like" complex particle. (2) Azobenzene groups attached on the surface of Silica-Guest could form inclusion complexation with a derivate ofβ-CD(6-SH-β-CD).Thus,there are many thiol groups anchored on SiO₂ surfaces.The gold nanoparticles with sodium citrate groups were found to self-assemble easily on the surfaces of the corresponding particles due to the interaction between the thiol groups and gold.As a result,we also obtained "raspberry-like" Au/SiO₂ complex particles with a SiO₂ particle as the core surounded by gold nanoparticles. Based on the Au/SiO₂ complex nanoparticles obtained by method(2),Polymer/ Au/SiO₂ trilayer complex particles were easily obtained by addition of the polymer chains with a thiol group at one end into Au/SiO₂ solutions.Finally,we prepared "Janus" gold nanoparticles by corrosion of SiO₂ core of the trilayer complex.3.Preparation of gold nanoparticles by using polypseudorataxane as a 'molecular template'.Cyclodextrins could form inclusion complexation with polymers with high selectivity.And so do cyclodextrin derivates.We synthesized polypseudorataxanes consisting of PPG and 6-SH-β-CD.Gold nanoparticles were prepared using the polypseudorataxanes as 'molecular templates' due to the thiol groups attached toβ-CD.We found that the structure of the molecular template plays an important role of aggregation state of the resultant gold nanoparticles.4.Self-assembly of metal nanopartieles on the toluene/water interfaceWe synthesizedα-CD andβ-CD modified gold nanoparticles with good water solubility.'Dendrimer' guest molecule with an azobenzen group at the end(C₁₂-Azo) was synthesized,which has good solubility in toluene.After mixing them together,the gold nanoparticles in water phase were transferred to toluene/water interface forming a film of gold nanoparticles due to the host-guest interaction between CD and Azo group.Furthermore,we found that mixing Oleic acid(OA) modified Fe₃O₄ in toluene andα-CD-AuNP in water together,a hybrid film consisting of Fe₃O₄ and AuNP was also formed easily by the interaction between OA andα-CD.5.Preparation of graft polymers via host-guest interactions.We synthesized water-soluble homopolymer PAA and functionalized its side groups withβ-CDs by chemical reaction.The homopolymers of PNIPAM and PEO with ADA at one end were also synthesized.We try to get 'non-covalent connected graft-polymers' driven by interactions between CDs on the PAA side groups and ADAs at one end of PNIPAM or PEO homopolymers.Further work could be done on the micellization of the graft polymers in water.