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Iron-catalyzed "Green" Atom Transfer Radical Polymerization

Posted on:2017-06-09Degree:DoctorType:Dissertation
Country:ChinaCandidate:J ZhouFull Text:PDF
GTID:1311330482494196Subject:Polymer Chemistry and Physics
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Atom radical transfer polymerization (ATRP) is a kind of controlled/"living" radical polymerization (CRP/LRP) mediated by trasition metal, which is widely used for obtaining well-defined polymers with designed molecular weights (Mn) and narrow molecular weight distributions (MWDs, Mw/Mn). In order to overcome some drawbacks of ATRP, a new facile polymerization method, called activators generated by electron transfer for ATRP (AGET ATRP) was developed based on normal ATRP. On account of using reducing agent (RA), AGET ATRP can using high valent metal catalyst and be conducted in presence of limited amount of catalyst, which greatly saves the cost and simplifies the operation of polymerization and purification of resultant polymers. "Green chemistry" is one of the most concerned topic in the development of chemical industries. A lot of studies had been done to promote the "green" characters of ATRP, such as reducing the amount of cayalyst, recycling catalyst, using more low-cost, eco-friendly, hypotoxicity agents, and improving reaction efficience and acitivity.In this dissertation, a series of works based on iron-catalyzed (abundance, biocompatibility, low cost and low toxicity) ATRP/AGET ATRP had been done to establish more "green" ATRP systems.The main contents and conclusions are summarized as follows:(1) A series of polar solvents containing amide group were used for FeBr2-catalyzed ATRP of MMA as both solvents and ligands. Most of the systems showed characteristics of "living"/controlled radical polymerization in the presence of limited amount of base. The results here confirmed the coordination potential of polar solvents containing the amide group to iron salts, and the formed catalyst complexes showed good activity. The structures of the polar solvents had a great effect on their coordination abilities, which is very important for the polymerization activity. The addition of an electron donor (methyl group) in the structures improved the solvents’activity significantly, which can be seen from the results when DMF, TMU, MPy and NMP were used. It is particularly interesting that the polymerizations remained controlled even when the polar solvents were reduced to a limited amount, which is of great significance for "green" applications.(2) Exploring the potential of alcohols used as reducing agent for FeBr3/DMF-catalyzed ATRP of MMA. The systems using ethanol or ethylene glycol (EG) had high reaction rate and well activity, but the polymerizations using methanol or glycerol ran slowly. Several initiators, such as EBPA, EBiB, MBiB, PEBr, were used for the alcohol-reduced systems. Most of the reactions behaved "living" features, and system using EBPA had the best result, which was resulted from its particular structure. The systems have well "green" characters due to using of alcohols.(3) A widely known "green" solvent, DMI was used as both solvent and ligand in the iron-catalyzed ATRP of MMA. The systems showed really high reaction efficiency and well characters of "living"V/controlled radical polymerization, even in the presence of limited amount of DMI and without base. The results here confirmed the coordination potential of DMI to iron salt, and forming high active catalyst complex. Iron(III)-catalyzed AGET ATRP of MMA using alcohols as RAs in DMI was also conducted. The selected alcohols, such as methanol, ethanol and glycerol, all behaved a certain reducing ability, and the polymerizations had relatively well controllability. In particular, glycerol behaved well reducing ability in spite of its high viscosity. Studies indicated that DMI could form deep eutectic solvent (DES) through hydrogen-bond interaction which increased the dissolvability of glycerol in the reaction solution. Then, we studied the potential of DES consisted of ChCl and urea as ligand used in FeBr2-catalyzed ATRP of MMA, and the polymerizations had well controllability in both Mn and MWDs, which successfully solved the problem of bad solubleness of urea in reaction solution.(4) A novel, significant base-mediated ATRP system without ligand was presented. When conducted in the presence of Na2CO3, NaHCCb, NaOH? K2CO3, KHCO3, KOH, Na3PO4, Na2HPO4 or NaH2PO4, the polymerizations of MMA catalyzed FeBr2 can progress successfully. Analyses of kinetic mechanism and resultant polymers indicated that the polymerizations were LRP. The effect of initiator on the polymerization was investigated as well. Most of the polymerizations behaved well controllability.The influence of different amount of base on the system was also studied. The polymerization rate increased along with the amount of base, and reached stable. The systems mediated by base had outstanding superiority because of the abandon of ligand, which greatly reducing the cost and potential hazard.
Keywords/Search Tags:Atom transfer tadical polymerization (ATRP), activators generated by electron transfer for ATRP (AGET ATRP), iron catalyst, polar solvent, alcohols, ligand-free
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