Studies On Synthesis, Self-assembly And Applications Of Branched Polymers

The studies on the synthesis of branched polymers, self-assembly of branched polymers in selected solvents and application of branched polymers in preparation of metal nanoparticles, modification of carbon nanotubes and recognition of anions are the chief aims of this thesis.In the past decades, the researches on the synthesis and applications of branched polymers have been the subject of much intensive research due to potential applications of branched polymers in catalyst, molecular recognition, and energy transfer. Benefiting from their unique 3D architectural, structural, and functional features, branched polymers are poised to make significant contributions in several areas of the physical and biological sciences and engineering. The research progress of the synthesis and applications of branched polymers were reviewed in this paper. Polyesters and polyethers branched polymers were synthesized and characterized by nuclear magnetic resonance (¹H-NMR and ¹³C-NMR), Fourier transform infrared spectra (FT-IR), ultraviolet-visible spectra (UV), gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and thermal degradation (TG) technologies. The microscopic and macroscopic self-assembly behaviors were analyzed by transmission electron micrographs (TEM) and optical microscope (OMS). The applications in preparation of metal nanoparticles, modification of carbon nanotubes and recognition of anions were also investigated.Poly(benzyl ether) dendrons with hydroxyl and carboxyl groups at the focal point have been synthesized by the convergent approach. The resultant dendrons have been characterized by element analysis, ¹H-NMR, FT-IR. The analytical data confirmed to the molecular structure of dendrons. The preparation of the novel polyhedron gold nanoparticles stabilized by the poly(benzyl ether) dendrons has been described. Varying the generation number of dendrons, concentration of precursor and reduction agent, can control the size and shape of the resultant nanoparticles. This strategy provides a synthetic route to prepare mental nanoparticles. We also describe a method to modification of multiwalled carbon nanotubes (MWNTs) using highlybranched molecules covalently attached onto the surface of MWNTs. The resultant MWNTs have substantial solubility in organic solvent and the method offers a new way to modification of MWNTs.The dendritic-linear polymers, poly(benzyl ether)-poly(methyl methacrylate) (Gn-PMMA) and poly(benzyl ether)-polystyrene (Gn-PSt), were synthesized successfully using the using dendritic chloric poly(benzyl ether) (G/-C1, GrCl and GrCl) as the macroinitiator through atom transfer radical polymerization (ATRP) approach. It was found that the temperature, reaction time, molar ratio of macroinitiator to monomer and the generation number of macroinitiator have significant effects on the molecular weights, conversion and polydispersity of resultant polymers. We found that the different aggregates can be formed in a mixed solvent for their solubility difference of dendritic and PMMA or PSt segments.We have designed two kinds of hyperbranched polymers (HPs), namely hyperbranched polyethers and hyperbranched polyesters, by cationic ring-opening polymerization and melt polycondensation, respectively. Then, chemical modifications of the HPs by benzoyl and toluene-4-sulfonyl groups were carried out through substituting a controlled fraction of the terminal hydroxyl groups of HPs. Detailed analysis revealed that self-assembled structures could be formed in the mixed solvent. Interestingly, we found that the macroscopic self-assembly structures of hyperbranched benzoyl-modified poly(3-ethyl-3-oxetanethanol) can be obtained via a simple solvent volatilizing route and generated multiwalled structures with millimeters in diameter and centimeters in length. The macroscopic self-assembly structures are stable reproducible. Meanwhile, the molecular structures, the nature of the solvent, the molecular concentration, the volatilizing ratio of solvent, and self-assembly temperature are also affected the self-assembly structures. The type of self-assembly describes here offers a synthetic route to well-defined one-dimensional organic macrostructures.Hyperbranched ferrocene-based polymers (FBHPs) with controlled molecular weights and properties have been prepared by an A2 + B3 approach by reacting ferrocene-l,l'-dicarboxylic chloride and trimethylopropane. The FBHPs have been evaluated by lH-MMR and 13C-NMR in order to determine the molecular component and the degree of branching. Because the ferrocene groups having redox-active properties, this hyperbranched polymer used to investigate the recognition of H2PO4" anion in solution was also described. These studies are important indeveloping novel polymer materials and their applications in anion recognition in biological system.