Study Of New Living/Controlled Radical Polymerization Induced By 9'9-bixanthene-diol (BIXAN)

Nowadays academics realm have recognized that controlled/living radical polymerization (LRP) is the superior method for the synthesis of structurally well-defined polymeric materials with well-controlled molecular weights and molecular weight dispersity under mild conditions, and it has a very improtant practical significance for scientific research. However the tranditonal living radical polymerization needs transiton metal as catalyst or uses colored compouneds to control the reation, there are some drawback, such as high cost, the fussy post-processing, and the harsh conditons. So the need for an effective living radical polymerization system with environmentally friend, low cost and good control is still urgent. This paper studies Cycloketyl Midiated living radical polymerization, whicn can control polymerization well under mild conditions, and it doesn't need any transition metal. This method presents important potential for practical large-scale production of industrial polymers. The main content is as follow:We improve the method of synthesis of BIXAN which is used as initiator and mediator in living radical polymerization. We confirm the most suitable ratio of THF:water= 5:3, ensuring the zinc overdose. We study various solvents on the solubility of the reagents, establish the use of ether as the solvent to dissolve and filtrate products and synthetize more than 99% purity of BIXAN initiator. By H1 NMR, we observe that the ratio of hydrogens at benzene ring and the hydroxyl is 2:1, consistent with the structure of BIXAN formula. Meantime, we use IR, MS and UV to characterize the structure of BIXAN.We study the features of bulk polymerization of MMA initiated by BIXAN, confirm the suitable temperature of polymerization is 65℃to 75℃and find that as the temperature increases, the polymerization rate increases, with narrow molecular weight distribution and improved controllability. At 70℃and 75℃, we use different concentrations of BIXAN for bulk polymerization, as the concentration of BIXAN increase, the deactivation rate accelerates, and we get good control effect. Under the condition of temperature of 75℃and the BIXAN concentration of 5%, we get the polymer of PDI close to 1.3. We find the concentration of the polymer chains increasing during the reactions, indicating that decomposition of BIXAN in the bulk polymerization is a process, with a "slow initiating" phenomenon.The decomposing of BIXAN becomes significantly faster in solution polymerization. When the conversions of monomers are over 50%, BIXAN all decomposes and changes into a polymer chain, and the concentration of polymer chains remains constant. The molecular weight increases and the distribution index decreases, linearly with the conversion. This is in line with the basic characteristics of living polymerization. By using toluene, THF, DMF and DMSO solvent respectively, we find that the low polarity of the solvent toluene could lead slow decomposition of BIXAN. And the molecular weight of polymer become much higher than the theoretical molecular weight; the decomposition rate of BIXAN increases in DMSO and DMF solvent, but the higher polarity of solvents cause too fast deactivation rate and lost the living end group of the polymer; the most suitable solvent is THF, and the polymer molecular weight increased linearly with the conversion and coincident with the theoretical molecular weight. At 70℃in THF solvent, distribution index decreases all the time, finally lower to 1.27.We carry out living radical polymerization of some other monomers, such as St, BA and MA. We also observe the molecular weights increase linearly with the conversions, and distribution index declines. In the evolution of GPC spectrum, we can see the peak positions shift to left with reaction time, which indicates the molecular weight increase. And the shape of peak becomes higher and sharper, indicating that the distribution index is decreasing. BIXAN can intiate a variety of monomers, the conditon is mild, with rapid polymerization rate, making it a very wide range of applications.By the reaction of BIXAN and macroinitiator with TEMPO, we confirm the production of free radicals and the mechanism of the polymerization belong to the dissociation/combination. We propose that BIXAN decomposes into free radicals, and the free radical initiate the first monomer, triggering the process of polymerization; we also study the formation of dormant species and the process of activation and deactivation, propose the concept of activation and deactivation constant rates, and explain the phenomenon of the molecular weight increasing and the distribution index decreasing by studing the process of activation and deactivation; by using three methods, TEMPO terminated, dynamics and formula of distribution index, we calculate the constant rate of activation, and there is no difference among the results by the three methods showing very good applicability. We also study the effect of temperature and solvent on the activation rate constant, finding that when increasing the temperatures, the constant rate of activation increases; both of the activation rate and deactivation rate in THF are relatively high. We propose a "slow initiating" effect on the polymerization and how to avoid it. Then by summing up the experimental data and experimental phenomenon, we propose a model of living radical polymerization by BIXAN initiator, and the mechanism of the effective radius maitaining the "stability" of pinacol radicals.By using two-component initiation system, we study the process of living radical polymerization with BIXAN and other common initiators, such as AIBN and ABVN. We find that the pinacol radicals can couple with propagating radicals and form polymer chain with two different end groups. By standard calibration curve of UV,we quantitatively calculate the number of living end group on polymers close to 1 and confirm that we sucessfully synthesize A-B polymer with one living end group by using two-component initiation system. In two-component initiator system, the polymer molecular weight increases linearly with the conversion, the distribution index gradually decreases. The conversion increases faster, which can reach 99% during the 300 minutes. By studing the different decomposition rate of AIBN and ABVN, we find that the initiator must have similar decomposition rate with BIXAN, so that we can get good control.One of the purposes of living radical polymerization is to synthesize the block copolymers, designing molecular structure. First, we study the effects of different concentration of initiator, monomer and solvent on the synthesis of the macroinitiators. In THF solvent,1% BIXAN,30% MMA, at 70℃, we synthesize the macroinitiator with the molecular weight 10596, and distribution index PDI 1.39. By 1H-NMR and UV, we prove that both ends of the polymer have the living fragment and the number is 2.036. Using the PMMA-BXIAN, we carry out the chain extension reaction of MMA and block copolymerization of BA, and the resulting polymer molecular weight increases linearly with the conversion, distribution index continuously decreases, close to 1.2 at last. During the polymerization, GPC spectra appears unimodal, indicating that all the polymer chains are involved in chain extension and block reaction and piancol remains stable.By studying the radical polymerization with BIXAN, we propose a new living radical polymerization method, with mild conditions, high activity and relatively stable. This new Cycloketyl radical polymerization initiated by BIXAN can control polymerization well, free from metal, presenting important potential for practical large-scale production of industrial.