Kinetics of RAFT Based Living Free Radical Polymerization and Application in Synthesis of Complex Architecture Polymer
|Course||Polymer Chemistry and Physics|
|Keywords||Polymerizable Dithioester The RAFT activity of free-radical polymerization Dynamics Coupling|
In recent years, the living radical polymerization has become one of the most popular spots for polymer synthesis. By reversible addition - fragmentation chain transfer (Reversible Addition-Fragmentation chain Transfer, RAFT) method, carry out the activity of the radical polymerization, the polymerization of the regulation effect, a relatively mild polymerization conditions, applicable to a wide range of monomers, can use a variety of polymerization method, and can be used to synthesis block, graft branched hyperbranched polymer having a specific structure. However, due to the less reagent RAFT chain transfer agent (the disulfide ester compound) product, the preparation process relates to a multi-step organic synthesis, and therefore limits its further development. The beginning of the study, as much as possible synthesis the various structures dithioester. And for the first time carried out a detailed study of different structures, different proportions of dithioester regulation living radical polymerization kinetics. The first use of the polymerization dithioester highly branched or hyperbranched polystyrene, and structural characterization. The major findings are as follows: (1) the type of the structure of the double thioester does double thioester group Z electrically negative influence on the polymerization reaction rate will affect the level of carbon-sulfur double thioester bond, thereby affecting double stability of the thioester; having a suction disulfide ester of the electron-withdrawing group will decrease the reaction rate, while double thioester push the electron-withdrawing group will accelerate the polymerization reaction, of course, not be too large electronegativity, or Z group is too large, electrically negative causes the polymerization reaction becomes uncontrollable. (2) we have found in experiments different concentrations of bis-thioester will also affect the rate of polymerization for the discovery RAFT reagent reaction intermediate to as primitives reaction to consider. Thus, we derive a new polymerization kinetics relationship, and has been consistent with the experimental results. Based on this result, we have proposed an amendment to the original RAFT polymerization theory. (3) Synthesis of polymerizable double thioester (4-vinyl benzyl dithiobenzoate), the use of the double thioester regulation polymerization of styrene, for the first time by a highly branched polystyrene with a controllable structure, obtained after degradation treatment, primary chain having a controllable molecular weight, molecular weight distribution and small characterized in living radical polymerization. (4) RAFT regulation of the polymerization reaction product the aminolysis processing, for the first time found that the product has twice the molecular weight of the polymer analyzed, it is found that the product is produced through the coupling reaction by a mercapto group-sulfur bond obtained. it is obtained by the reduction of acetic acid and zinc to obtain the same polymer molecular weight before coupling. (5) The copolymerization reaction of the polymerizable double thioester with styrene, using infrared quantitative techniques, and determination of the two monomers in the copolymerization reaction system reactivity ratio. (6) branched product was added to the styrene and the amount of initiator, can be re-growth, to obtain a high molecular weight branched product, after processing them, find its still comply with the controlled radical polymerization. (7) can be self-polymerization of the polymerizable double thioester, the hyperbranched polymer can be obtained if the reaction conversion rate exceeds a certain range, the crosslinked product is obtained. This further proves that the termination of the reaction of the intermediate radical. lt; WP = gt; (8) Synthesis of over thiodiphenyl methylthio acyloxy use it directly regulating the polymerization reaction, and found that the reaction has an induction period, but still meets the living radical polymerization. By adjusting the proportion of initiator, can eliminate the induction period to accelerate the reaction rate.