Hou Zhaomin group of Japan Institute of science and chemistry and Luo Yi group of Dalian University of Technology

Compared with linear polymer, ring polymer has unique structure and performance Therefore, the synthesis of cyclic polymers has been widely concerned in both academic and industrial fields However, the synthesis methods of cyclic polymers are limited, especially the successful synthesis of functionalized and micro structured cyclic polymers Recently, the research group of Professor Hou Zhaomin of Japan Institute of science and chemistry has prepared functionalized cyclic polymers with high selectivity through controllable polymerization of functional α, ω - diene In cooperation with Professor Luo Yi of Dalian University of technology, the detailed mechanism of the polymerization has been revealed at the molecular level (j.am.chem.soc., 2019, DOI: 10.1021/jacs.9b04275) Introduction to Professor Hou Zhaomin, Professor Hou Zhaomin, director of the Research Office of mechanochemistry in Japan, Deputy director of the center of sustainable resources science, director of advanced catalysis research room of the center of sustainable resources science, chairman of Japan rare earth Association, distinguished professor of Dalian University of technology, Chair Professor of Yangtze River scholar, visiting professor of Tokyo University of technology, Kyoto University, Saitama University, Peking University, etc Hou Zhaomin group carried out a series of research work in the field of organometallic chemistry around new catalysts, new reactions and new materials, and achieved a series of important results In particular, breakthroughs have been made in olefin catalytic polymerization A number of rare earth catalysts and new materials with good application prospects have been developed Some products have completed industrial scale-up experiments and entered the industrialization stage At present, more than 250 papers have been published, of which more than 70 have been published in journals with more than 10 influencing factors, such as Science, Nature and Nature Chem., and nearly 60 have been published in the international top journals of chemistry, i.e Journal of American Chemical Society and German applied chemistry More than 12000 papers have been cited, and more than 30 papers have been cited more than 100 times for a single paper, with an H-index of 65 For his outstanding contributions in the field of organometallic chemistry, Professor Hou Zhaomin has successively won the Japanese Society for academic revitalization award, Mitsui chemical catalysis science award, Japanese Minister of science and technology award, Japanese Rare Earth Society Award, Japanese polymer Society Award, and "Huang yaozeng Metal Organic Chemistry Award" of Chinese chemical society , Nagoya Silver Award, Japan Chemical Society Award and other honors and awards Leading scientific research achievements: scandium catalyzed high area and high stereoselective cyclization polymerization of α, ω - diene and its controlled copolymerization with ethylene A series of functionalized poly (α - olefins) and ethylene polar α - olefin copolymers containing heteroatoms (oxygen, sulfur, selenium, nitrogen, phosphine) were successfully and selectively synthesized by the strategy of polymerization (hop) (SCI Adv 2017, 3, E1701011), and through the cooperation with Luo Yi, Professor of Dalian University of technology, the micro mechanism of heteroatom assisted olefin polymerization was revealed based on DFT calculation Subsequently, the group successfully synthesized high molecular weight, high polar monomer content ethylene substituted propylene copolymers by using scandium catalyst to realize high-efficiency copolymerization of ethylene and anisole propylene Surprisingly, this kind of copolymer is a kind of intelligent polymer material with high strength, high tensile strength, shape memory and rapid self-healing performance Its self-healing ability is almost unaffected by the environment, and it can be effectively healed in air, water, acid and alkali solutions, with a broad potential application prospect (j.am.chem.soc., 2019, 141, 3249) On this basis, through the ingenious design of monomers and the coordination of heteroatoms (oxygen and sulfur) in the functional group with the metal center of the catalyst, the selective coordination insertion of two C = C double bonds in α, ω - diene was realized, and the ternary ring structure containing 1,2,4-cis (containing oxygen polymer) and 1,2-trans-1 were prepared respectively, 4 cyclic polymer with CIS trisubstituted five membered ring structure (sulfur containing polymer) (Fig 1) In this polymerization process, through the coordination of heteroatom and metal in the end ring-forming monomer, the selectivity of coordination insertion of the second molecular monomer was successfully induced, and the high stereoregularity of the polymer chain was achieved The copolymers with high molecular weight and controllable structure were successfully prepared (j.am.chem.soc., 2019, 141, 12624-12633; doi: 10.1021/jacs.9b04275) Fig 1 Scandium catalyzed functionalized polymerization of α, ω - diene and copolymerization with ethylene (source: J am Chem SOC.) the author first used 4-benzyloxy-1,6-heptadiene as monomer to study the catalytic polymerization performance of three scandium catalysts with different cyclopentadienyl ligands The results showed that when c5me4tms with the largest steric hindrance was used as the ligand, scandium catalyst showed better controllability of cyclization polymerization, and the ring polymer with molecular weight of 18.7-86.5 kg / mol was obtained The content of 1,2,4-cis-trisubstituted five membered ring structure in the polymer is 94% (Fig 2 A) by NMR, the single carbon spectrum signal of the main structure shows that the polymer has a high stereoregularity (MMM = 95%), and the differential scanning calorimetry (DSC) shows that the polymer is a semi crystalline material with a melting point of 122-125 ° C The polymerization of α, ω - diene containing other heteroatom functionalization was also attempted The results showed that the regioselectivity of the polymer changed obviously when the substituent group was phenylthiol group The NMR spectrum (Fig 2 B) confirmed that the polymer mainly contained 1,2 trans-1,4 CIS trisubstituted five membered ring structure (94%), and also had high stereoregularity (RRR = 95%) Differential scanning calorimetry (DSC) showed that the melting point range of the polymer was 152-156 ° C Fig 2 NMR characterization of cyclic polymers (source: J am Chem SOC.) in order to reveal the reason of high regioselective and stereoselective cyclization Polymerization Catalyzed by scandium and the mechanism of heteroatom assisted polymerization, the research group, in cooperation with Luo Yi, Professor of Dalian University of technology, conducted DFT calculation on the polymerization process of oxygen-containing and sulfur-containing monomers (Fig 3) The results show that the heteroatoms and the first double bond of the two kinds of monomers have different enantioselectivity when they coordinate with scandium When a double bond in diene is inserted, the 4-achiral carbon will produce the chiral center due to the desymmetric effect When the monomers contain phenylthio substituents, the energy of si-bs (1s, 4R) products is low after the first double bond is inserted through Si coordination and 2,1-insertion Then, the second double bond in si-bs (1s, 4R) molecule is Si coordinated, and through the transition state si-ts-cs (1s, 2S, 4R) (Δ g ≠ = 12.6 kcal / mol), a 1,2 trans-1,4 CIS substituted five membered ring si-ds (1s, 2S, 4R) is formed The second molecular monomer chain grows in the same coordination insertion mode, and the isotactic polymer is finally obtained Figure 3 DFT calculation of cyclization polymerization of phenylthiomonomers (source: J am Chem SOC.) when the monomer substituent is benzyloxy, after the first double bond 2,1-is inserted, benzyloxy monomers tend to form Si-B o (1 s, 4 R) configuration products At this time, the second double bond in Si-B o (1s, 4R) molecule has a lower coordination energy of re configuration Through the transition state of re-ts-co (1s, 2R, 4S) (Δ g ≠ = 9.7 kcal / mol), the 1,2,4 CIS substituted five membered ring structure of re-do (1s, 2R, 4S) is obtained It can be seen from the calculation that the second molecular monomer is inserted in the same mode and the isotactic polymer is finally obtained Figure 4 DFT calculation of cyclization polymerization of phenoxy monomers (source: J am Chem SOC.) Figure 5 Cyclization copolymerization of functionalized α, ω - diene and ethylene (source: J am Chem SOC.) in addition, the author also studied the cyclization copolymerization reaction of functionalized α, ω - diene and ethylene The results showed that the copolymers obtained from the reaction of O-2 and ethylene showed high activity, high ring structure content (9-25 mol%) and high molecular weight (Mn = 55.9-147.9 kg / mol) at 1 atm ethylene pressure NMR spectra showed that there was no unreacted double bond in the polymer, that is, in the presence of ethylene, all the monomers were still completely cyclized The polymer mainly contains isolated ring-shaped units, without adjacent ring-shaped unit chain segments When the comonomer is S-2 substituted by phenylthiol, the content of functionalized ring structure can be controlled by adjusting the ratio of monomer and catalyst (the content of ring structure is 19-77 mol%) The resulting copolymer structure is random copolymer In this paper, scandium complex with large resistance cyclopentadienyl coordination was used as catalyst Through the coordination of Scandium with heteroatom in monomer, the high regioselective and stereoselective polymerization of functionalized α, ω - diene and its controllable copolymerization with ethylene were successfully realized A variety of cyclic polymers and ethylene copolymers with different microstructures were synthesized This work was published on J am Chem SOC (2019, 141, 12624-12633; doi: 10.1021/jacs 9b04275) under the title of "scandium catalyzed regio - and stereo selective cyclopolymerization of functional α, ω - dienes and cyclopolymerization with ethylene" The first author is Dr Wang haobing of Japan Institute of science and chemistry, and Dr Zhao Yanan of Dalian University of technology is the co first author of the work The corresponding authors are Professor Hou Zhaomin of Japan Institute of science and chemistry and Professor Luo Yi of Dalian University of technology The research was supported by the Japan Society for academic revitalization and the National Natural Science Foundation of China (author: haobing Wang, Yanan Zhao, Masayoshi nishiura, Yang Yang, Gen Luo, Yi Luo, Zhaomin Hou).