Study On The Self-Assembly Behavior Of Amphiphilic Copolymer Containing Cross-Linked Hydrophilic Block In Solution

The self-assembling behavior of amphiphilic block copolymers in solution isone of the hottest topics of polymer science in recent years. It's well known thatamphiphilic block copolymers can form micelles or colloidal size aggregates insolvent selective for one of the blocks. The morphology and size of theaggregates are dependent on the composition and concentration of the blockcopolymers, the property of solvent, temperature and additives. Blockcopolymers can form micelle-like aggregates in aqueous media, or reversemicelles when the copolymers were dissolved in a low polarity solvent. Based onthe relative block length of the copolymer, two types of micelles can bedistinguished: one is star micelle;the other is crew-cut micelle.Semiconductor nanoparticles have potential applications in fabricatingdevices with magnetic, optical, and electric properties especially as nonlinearoptical materials. While block copolymer self-assembly system is one of themost useful systems for the preparation of uniform semiconductor nanoparticles.Hybrid systems constituting self-assembled amphiphilic block copolymers andmetal/semiconductor nanoparticles are important in modern material science andare extensively investigated.In Chapter Two, we described the synthesis and characterization of theamphiphilic copolymer containing cross-linked hydrophilic block: poly (methylmethacrylate)-block-poly (lead dimethacrylate) (PMMA-b-PLDMA). Bytwo-step sequential atom transfer radical polymerization (ATRP),PMMA-b-PLDMA was synthesized in solution. Because that there are two C=Cbonds in each LDMA molecule, introducing a cross-linked PLDMA block in thepolymerization procedure, the hydrophilic block of the copolymer is cross-linkedand the hydrophobic block is linear. When the content of hydrophilic block incopolymer is larger, the solubility of the copolymer became worse. So theamphiphilic copolymer PMMA-b-PMAA with a low polydispersity wassynthesized by ion exchange, after putting the copolymer PMMA-b-PLDMA dipin hydrochloric acid for one day. And then the micelles of PMMA-b-PMAA wereprepared in water by dialysis.In Chapter Three, we investigate the self-assembly behavior of this novelblock copolymer PMMA-b-PLDMA. And maybe the cross-linked hydrophilicblock will influence the self-assembling behaviors of the amphiphilic blockcopolymer. Since one of the monomer is LDMA, the metal ions are bound to thehydrophilic block during the synthesis process, we do not need to incorporatemetal ions into the micelle core or corona like other groups, and thus theexperiment procedure can be simplified. Then we prepared PbSnanoparticles/polymer composite aggregate through self-assembly of the novelcopolymer, and the amount of PbS nanoparticles can also be easily tuned bychanging the content of the hydrophilic block.In Chapter Four, we realized the self-assembly of the amphiphiliccopolymer with cross-linked hydrophilic block in ethanol through a simplemethod which is selective volatilization of chloroform. After the chloroform wascompletely volatilizable, the steady micelles were prepared in ethanol. Comparedwith the traditional dialysis method, we not only simplified the experimentalprocedure, but also realized the preparation of micelle in friendly solvent(ethanol). The experiment results show that the size and morphology of theresulting micelles or micelle aggregates in ethanol are ascribed to content of theethanol and the nature of the solvent mixture. Through reacting with H2S gas,PbS nanoparticles were formed in the micelles in situ.In summary, based on the different methods, we prepared the micelles of theamphiphilic copolymer with cross-linked hydrophilic block in water and ethanol.By the way of reacting with H2S gas, the PbS nanoparticles/micelle compositematerials were prepared in situ. By this technique, we anticipate that this facileblock copolymer can be exploited for the fabrication of multifunctional polymernanocomposite particles in friendly solvents.