Study On Preparation And Characterization Of Functional Nanocomposite Based On The Block Copolymers

Controlled synthesis of the copolymer is mainly controlling the structure and the molecules weight of the copolymer. Living radical copolymerization is one of the ideal ways to synthesis the copolymer with low polydispersity and predetermined molecules weight. Block copolymers with predetermined structure and series can be easily synthesized via living radical copolymerization, so considerable attentions have been paid to the study on it. Atom transfer radical copolymerization (ATRP) is the ideal method to carry out living copolymerization, which can realize most of the monomers to be freely/controlled radical copolymerization.Amphiphilic block copolymer can be self-assembles in selective solvents to form various morphologies, such as nanothread, cylinder, shell-core, sphere, etc, so, preparing of block copolymers and controlling their morphorgies have aroused many scientists extensive interests. The reality of the occurring and controlling of various morphologies of BAB block copolymers is not only significant to the foundation of the amphiphilic copolymers to self-assemble, but also potential to apply to control synthesis the nanomaterials. The physical and chemical properties of the nanomaterials are different with the bulk materials in many fields, such as the magnetic property, superconductive property, optical and electronic property, and the phase change temperature, etc, especially to the semiconductor, its unique optical and electronic properties have aroused many scientists extensive interests. Composite materials have many good properties, such as high intensity and high modulus, good chemical stability, good high temperature property and many others unique properties. Those good properties of composite materials could be achieved by complementing the properties of the components, which are not be processed by the components. The research work could be divided into four parts as the following:1. A series of PS-b-PEG-b-PS triblock copolymers were synthesized via atom transfer radical polymerization (ATRP). This was achieved by using the esterification of poly (ethylene glycol) with 2-Bromopropionyl bromine as macroinitiators, styrene as monomer, CuBr/2,2'-bipyridine as the catalysts at 110 ℃. The structure, the molecules weight, and the polydispersity of the products were characterized. The results revealedthat the catalytic system could well catalyze styrene to polymerize. The Mn increased with the conversion of the monomer increasing, whiling the polydispersity index (PDI) was 1.19.2. A series of PMEG-fc-PAN and PAN-6-PEG-6-PAN block copolymers were synthesized by using atom transfer radical polymerization (ATRP). This was achieved by using the esterification of poly (ethylene glycol) monomethyl ether and poly (ethylene glycol) with 2-Bromopropionyl bromine as macroinitiators respectively, acrylonitrile as monomer, CuBr/2,2'-bipyridine as the catalysts and ethylene carbonate (EC) as solvent at 70 °C. The structure, the molecules weight, and the polydispersity of the products were characterized. The Afn increased but the convension kept unchanging almost with the quantity of the monomer increasing, the possible reason was due to the predominant effect of the initiator efficiency over the effect of the increasing quantity of the monomer under the circumstances that the quantity of the macroinitiators and the solvent kept constant, but the quantity of the monomer increased. The kinetic curve revealed that the Mn increased approximately linearly and the PDI kept constant with the conversion increasing while the quanlity of the monomer kept constant, which indicated that the polymerization processing to be freely/controlled polymerization.3. Silver nanoparticles with the average diameter of 17 nm were synthesized by using amphiphilic block copolymer PAN-6-PEG-fc-PAN (PEA) based on the flexibility of the copolymer chains and the complex effect of -CN in the polyacrylonitrile with Ag+ and Ag under ultrasonic irradiation. The product was characterized by X-Ray Diffraction (XRD), Fourier Transfer Infrared Spectrometer (FT-IR), Transmission Electron Microscope (TEM), UV-Vis spectrum and Thermal Gravity Analysis (TGA). The FT-IR results revealed that the backbone of the PEA block copolymer was not be cleavage during the synthesis of the silver nanoparticles under ultrasonic irradiation. The TEM results revealed that the size and size distribution of the resulting silver nanoparticles prepared basing on the copolymer were strongly dependent on the initial concentration of the silver ion solution and the irradiation conditions. Low initial silver ion concentration allowed for yielding silver nanoparticles with a small size and the size of the silver nanoparticles increased with the concentration of the silver ion solution increasing. The silver crystal was polycrystalline with a cubic structure, as confirmed by XRD.4. CdSe nanocrystals are good semiconductors made by the group II-IVelements and widely used in the fields of the optical materials, solar materials and sensors. CdSe nanocrystals were synthesized by using amphiphilic block copolymer PAN-fe-PEG-6-PAN (PEA) as stabilizer via chemical processing. The product was characterized by X-Ray Diffraction (XRD), Fourier Transfer Infrared Spectrometer (FT-IR), High Resolution Transmission Electron Microscope (HRTEM), Thermal Gravity Analysis (TGA), UV-Vis and Fluorescence spectrum. HRTEM results revealed that the morphologies of the resulting CdSe nanocrystals were continuous crystal lattice. UV-Vis and Fluorescence results indicated that the CdSe nanocrystals blue shifted owing to their quantum size effects. TGA results revealed thermal stability of the polymer enhanced abviously after introducing the CdSe nanocrystals.