Synthesis,Self-assembly And Application Of Disulfide-Containing Random Copolymers In Nanocrystal

Nanocrystalline hybrid materials have received more and more intensive attention and become one of the most widely studied nanomaterials,due to their unique surface effects,strong oxidation resistance,local surface plasmon resonance effects,excellent fluorescence stability,biocompatibility,less toxicity,which have great potential application value and research significance in many fields such as medical diagnosis,biological detection,biomarker,environmental monitoring,nanosensors,and construction of new materials.However,the disadvantages of agglomeration and poor stability in aqueous solution severely restrict the application of water-soluble nanocrystalline hybrid particles.Therefore,it is imperative to prepare uniformly dispersed and stable hybrid nanoparticles in the aqueous phase.In this paper,reactive monomers containing disulfide bonds,aldehyde groups and amino groups were designed and synthesized successfully.By using these monomers,two kinds of amphiphilic random copolymers were prepared by reversible addition fragmentation chain transfer(RAFT)polymerization to modify gold nanoparticles and quantum dots.The specific achievements of this paper are shown as follows:1.Reactive monomers MALA,MAHA,and MABA were prepared through the structure designation by using lipoic acid,hydroxyethyl methacrylate,methacryloyl chloride,p-hydroxybenzaldehyde and p-nitrophenol.The structures of MALA,MAHA and MABA were characterized by 1H-NMR and FTIR.2.Using the above synthesized polymerizable monomers and polyethylene glycol methacrylate(MAPEG)as raw materials,a series of amphiphilic random copolymers P(MAPEG-co-MALA-co-MAHA)with different degrees of polymerization were obtained by RAFT polymerization respectively.At the same time,nitro groups of the amphiphilic random copolymer precursors were reduced to amino groups by further using aminated formic acid to obtain P(MAPEG-co-MALA-co-MABA)with different degrees of polymerization finally.The synthesis of amphiphilic random copolymers was successfully verified by 1H-NMR,FT-IR and GPC.Furthermore,gold nanoparticles with uniform size and particle size of about 35 nm were prepared by the classical sodium citrate aqueous-reduction method.3.Spherical micelles with core-shell structure were prepared by self-assembly process based on the two kinds of amphiphilic random copolymers.The critical micelle concentration(CMC)was determined with Nile Red as the fluorescent probe.Using DLS and TEM,the influences of different degree of polymerization of the amphiphilic random copolymers on micellar morphology and size were discussed.The results indicated that the self-assembled micelles of amphiphilic random copolymer P(MAPEG-co-MALA-co-MABA)have more distinct core-shell structure and uniform particle size than micelles of P(MAPEG-co-MALA-co-MAHA).In addition,as polysulfide ligands,five-membered heterocycle of the synthesized P(MAPEG-co-MALA-co-MAHA)and P(MAPEG-co-MALA-co-MABA)were reduced to obtain amphiphilic polysulfhydryl ligands by the photochemical reaction apparatus.The ligand exchange between gold nanoparticles or oil-soluble quantum dots(ZnCdSe/ZnS)and amphiphilic polysulfhydryl ligands were achieved to prepare water-soluble nanoparticles.The effects of different degrees of polymerization of the amphiphilic random copolymers on the morphology and stability of the nanomaterials were investigated by means of TEM,DLS,UV-Vis and fluorescence spectra.The results showed that the absorption peaks of the nanoparticles generated bathochromic shift in ultraviolet visible absorption spectrum to different degrees,and the dispersion and stability in the aqueous phase were gradually improved with the increasing of the hydrophilic segment of MAPEG.4.The reaction between aldehyde groups of Au@P1 nanoparticles and amino groups of Au@P2 nanoparticles,or aldehyde groups of QD@P1 nanoparticles and amino groups of Au@P2 nanoparticles were used to second-assembly and build self-assembled nanocrystal hybrid micelle aggregates containing imine bond structure.The morphological and optical properties of self-assembled nanocrystal hybrid micelle aggregates were discussed by TEM,DLS,UV-Vis and fluorescence spectroscopy.The results indicated that most of the secondary assembled structures were dimers and trimers,which had good dispersibility and stability in the aqueous phase.