Synthesis And Properties Of Amphiphilic Copolymers With Special Architectures Based On The PEO-Supported Multifunctional-initiating System

Design and synthesis of amphiphilic copolymer with complex architecture are always pursued by polymer chemists in past decades. Thanks to the development of living polymerization, combining the living radical polymerization with ionic polymerization, some linear and nonlinear (such as comb-like, star, dendritic, hyperbranch) copolymers are synthesized. These special architectural copolymers may form abundant morphologies in selective solvent or in bulk and have potential applications in chemistry, physics and biology. In these amphiphilic copolymers, poly(ethylene oxide) (PEO) is an important composition for its good solubility in both water and most organic solvents. However, most of amphiphilic graft copolymers were composed of hydrophobic backbone and hydrophilic side chains. The inverse architecture was scarcely reported due to the synthesis difficulty. On the other hand, or the amphiphilic multiblock copolymers, the synthesis is solely confined in polycondesation of prepolymers. It is still a challenge to explore a simple and effective way to synthesize these copolymers via living polymerization. Herein, by means of PEO-supported multifunctional-initiating system, some novel well-defined amphiphilic copolymers with complex architectures are synthesized and their properties are explored. The main results have been obtained as follows:1. A heterofunctional monomer 4-glycidyl-2,2,6,6-tetramethyl piperidyl-1-oxyl, (GTEMPO) was synthesized and copolymerized with ethylene oxide (EO) using 2-(2-methoxyethoxyl) ethanol potassium as initiator. The resultant copolymer poly(GTEMPO-co-EO) with many pending TEMPO groups was used to monitor the graft polymerization of styrene. A serial amphiphilic graft copolymers with different molecular weight named as PEO-g-PS were prepared. The investigation ofkinetics of the grafting polymerization of styrene confirmed that the polymerization was under control. However the coupling of propagation radical was observed in the long polymerization time and the high conversion.2. GTEMPO and EO were copolymerized using di(ethylene glycol) potassium as initiator. Linear α, ω-didydroxyl poly(GTEMPO-co-EO) was obtained. Then in the presence of powdery KOH, cyclization reaction was carried out in pseudo-high-dilute CH₂Cl₂ solution and l-poly(GTEMPO-co-EO) was converted to c-poly(GTEMPO-co-EO). After purification, c-poly(GTEMPO-co-EO) was used to control the polymerization of styrene and the target amphiphilic macrocyclic graft copolymer c-PEO-g-PS was obtained. The cmc of c-PEO-g-PS was determined by using pyrene as fluorescence probe. The morphologies of copolymer c-PEO-g-PS in water were observed and the diameter of spheric micelle was about 200 nm. UV-Vis spectra confirmed that macrocyclic graft copolymer c-PEO-g-PS showed the higher extraction efficiency for the dyes from the aqueous solution than that of PEO-g-PS and comb-like graft copolymer PEO-g-PS.3. The multiblock PEO macro-RAFT agent with embedded BDATC (PEO-b-CTA)_n was synthesized via the condensation of α,ω-dihydroxyl PEO with BDATC-acetyl chloride, and styrene was polymerized then by using this macro-RAFT agent, and a serial of (AB)_n type binary multiblock copolymer (PEO-b-PS)_n with different molecular weight was obtained. The (PEO-b-PS)_n can be continuously used as macro-RAFT agent to monitor the polymerization of t-butyl acrylate to give the (ABCB)_n type ternary multiblock copolymer (PEO-b-PS-b-PtBA-b-PS)_n. After hydrolysis of PtBA blocks, amphiphilic multiblock copolymer (PEO-b-PS-b-PAA-b-PS)_n was obtained. It was confirmed that the polymerization of styrene in the presence of (PEO-b-CTA)_n was under control. It was found that the self-assembly morphologies of binary copolymer (PEO-b-PS)_n in water were strongly depending on the component of the (PEO-b-PS)_n, and water content also affected the morphologies and induced the variation of morphology in diameter and shape. Ternary amphiphilic multiblock copolymer (PEO-b-PS-b-PAA-b-PS)_n was used as templates to fabricate the silver nanoparticles. After the addition of the copolymer, silver can form the spherical nanoparticles with uniform diameter.