Functional polymers and surfaces by atom transfer radical polymerization.

摘要

Atom transfer radical polymerization (ATRP) has been established as a powerful technique to prepare a variety of polymers with predetermined molecular weight, narrow molecular distribution, high functionality, and complex architecture. The objective of this thesis has been to further understand the polymerization mechanism and apply this technique to prepare well-defined functional polymeric materials such as novel block copolymers, bio-related materials, and functional surfaces. It was realized that the understanding of the kinetics and the mechanism of the ATRP is a key issue in applying it to the preparation of polymeric materials with the well-defined structures and designed properties. ATRP relies on the reversible reaction of a low-oxidation state metal complex with an alkyl halide generating radicals and the corresponding high-oxidation state metal complex. The transition metal complex is one of the main factors which determine the control of the polymerization. Ligands that complex with the transition metal play a crucial role in determining the nature of the catalyst including its structure, catalyst activity, and solubility. Therefore it is crucially important to understand the role ligand plays in the polymerization. My thesis work started with mechanistic studies aimed at further understanding the effects of the ligands and solvents on the polymerization and optimizing the reaction conditions and progressed toward the synthesis of unique polymers and functional surfaces by ATRP in solution or on the surface. This thesis is composed of three main subjects: mechanistic studies of ATRP and the synthesis of well-defined block copolymers (Chapters 1 to 3); the synthesis of bio-related polymeric materials, including polymers with biocompatible functional groups and degradable polymers (Chapters 4 to 5); the preparation of functional surfaces including antibacterial ones and thermo-responsive ones (Chapters 6 to 7).; Chapter 1 of this thesis summarized the kinetics of ATRP of n-butyl acrylate (nBA) using a Cu(I)Br/N,N,N',N",N"-pentamethyldiethylenetriamine (PMDETA) based catalyst system and methyl-2-bromopropionate (MBrP) as initiator.; Based on this understanding of the mechanism and optimized polymerization conditions, we used ATRP to prepare novel block copolymers. In chapter 2, well-defined styrene (S) and nBA linear and star-like block copolymers were synthesized via ATRP using di- and trifunctional alkyl halide initiators employing the Cu/PMDETA catalyst system. Initial addition of Cu(II) deactivator and utilization of halogen exchange techniques suppressed the coupling of radicals and improved cross-propagation to a large extent, resulting in good control over the polymerization.; In chapter 3, a well-defined poly(ethylene oxide) (PEO)-b-PS block copolymer and PS-poly(arylic acid) block brush were synthesized. Both polymers formed well-structured micelles in a shell-selective solvent (water or methanol). Subsequent UV irradiation of the micelles led to cross-linking of the PS core of the micelle. After pyrolysis, the cross-linked PS core was converted to partially graphic carbon while the shell was sacrificed, resulting in formation of discrete carbon nanoparticles and nanorods.; ATRP of dimethyl(1-ethoxycarbonyl)vinyl phosphate (DECVP) was investigated in the presence of different catalyst systems and initiators (Chapter 4). Polymers with controlled molecular weight and relatively low polydispersity (PDI 1.5) were obtained through ATRP initiated with ethyl 2-bromoisobutyrate (EBriBu) in the presence of Cu(I)Cl/2,2'-bipyridine (bpy).; In chapter 5, the investigation of degradable polymers with well-defined structure by combining radical ring-opening polymerization (RROP) and ATRP was described. The polymerization behavior of two types of cyclic monomers, 5-methylene-2-phenyl-1,3-dioxolan-4-one (MPDO) and 5,6-benzo-2-methylene-1,3-dioxepane (BMDO) have been thoroughly studied.; In chapter 6, ATRP was explored