Xiao-Dong Fan_PMS-BT 2019

Biography
Prof. Xiao-Dong Fan North Western Polytechnical University, China
Title: Syntheses of Butadiene Based Reactive Polymer Containing high 1,4 Unit Stereo Structure and its Related Block Copolymers via Developing Advanced Initiator Strategy
Abstract: In order to study the influence of steric structural factors of mono-lithium based anionic initiators on the total 1,4 unit content in hydroxyl terminated polybutadiene (HTPB), a series of precursors with different steric volume were designed and synthesized. The precursors were allowed to react with lithium in cyclohexane at 60 ○C to prepare mono-lithium based initiators. By using the initiators prepared, HTPB was synthesized via anionic polymerization of 1,3-butadiene in cyclohexane. The structure and 1,4 unit content were characterized by SEC-MALLS and 1H NMR. It was found that the content of the 1,4 unit in HTPB was markedly increased with an increase in the initiator's steric volume. It was the initiator’s larger steric hindrance that could block lithium’s intermolecular association with monomers during anionic polymerization; as a result, effectively increased the 1,4 unit content in HTPB. For synthesis a higher cis 1,4 unit content (over 90%) of HTPB, a novel Ni-based initiator was designed and synthesized. By investigating the effect of the butadiene skeleton structure and initiator’s counterion on initiating efficiency, it is found that [3-Ni(CH2CHCHCH2OOCH3)][BPhF ] complex is a feasible combination to constitute a complex initiator. 1H-NMR data proved that the initiator’s structure is in accordance with the original design. The data of 13C-NMR confirmed that HTPB synthesized not only gained a significant amount of cis-1,4 unit content >(90%) compared with the HTPBs by free radical and anionic polymerizations, but also its molecular weight and molecular weight distribution can be effectively controlled. A new strategy to synthesize random and alternating multiblock copolymers (MBCs) by the polycondensation of macromonomers’ terminal hydroxyl groups using [CpRu(CH3CN)3]PF6/quinaldic acid as the catalyst was studied. By using this special catalyst, the syntheses of both random and alternating α,ω-dihydroxy MBCs were conducted by using the coupling chemistry of α,ω-dihydroxy compounds. This dehydration synthesis between the two terminal hydroxyl groups not only ensures the successful preparation of MBCs, but also can guarantee to form α,ω-dihydroxy polymers. At the same time, the preparation of a hydroxyl terminated polystyrene-b-polybutadiene- b-polystyrene triblock copolymer (SBS) with high cis-1, 4 content via a novel nickel catalyst, [η3-Ni(CH2CHCHCH2OOCH3)][BPhF4] was also revealed. FT-IR, 1H-NMR, and 13C NMR indicated that the polybutadiene segment of the copolymer contains greater than 90% cis-1, 4 structure indicating achievement of this research goal. Toward the functionalization purpose, the results indicated that hydroxyl groups were successfully introduced into the terminals of the triblock copolymer (HO–SBS–OH).

Biography

Prof. Xiao-Dong Fan
North Western Polytechnical University, China

Title: Syntheses of Butadiene Based Reactive Polymer Containing high 1,4 Unit Stereo Structure and its Related Block Copolymers via Developing Advanced Initiator Strategy

Abstract:

In order to study the influence of steric structural factors of mono-lithium based anionic initiators on the total 1,4 unit content in hydroxyl terminated polybutadiene (HTPB), a series of precursors with different steric volume were designed and synthesized. The precursors were allowed to react with lithium in cyclohexane at 60 ○C to prepare mono-lithium based initiators. By using the initiators prepared, HTPB was synthesized via anionic polymerization of 1,3-butadiene in cyclohexane. The structure and 1,4 unit content were characterized by SEC-MALLS and 1H NMR. It was found that the content of the 1,4 unit in HTPB was markedly increased with an increase in the initiator's steric volume. It was the initiator’s larger steric hindrance that could block lithium’s intermolecular association with monomers during anionic polymerization; as a result, effectively increased the 1,4 unit content in HTPB.

For synthesis a higher cis 1,4 unit content (over 90%) of HTPB, a novel Ni-based initiator was designed and synthesized. By investigating the effect of the butadiene skeleton structure and initiator’s counterion on initiating efficiency, it is found that [3-Ni(CH2CHCHCH2OOCH3)][BPhF ] complex is a feasible combination to constitute a complex initiator. 1H-NMR data proved that the initiator’s structure is in accordance with the original design. The data of 13C-NMR confirmed that HTPB synthesized not only gained a significant amount of cis-1,4 unit content >(90%) compared with the HTPBs by free radical and anionic polymerizations, but also its molecular weight and molecular weight distribution can be effectively controlled.

A new strategy to synthesize random and alternating multiblock copolymers (MBCs) by the polycondensation of macromonomers’ terminal hydroxyl groups using [CpRu(CH3CN)3]PF6/quinaldic acid as the catalyst was studied. By using this special catalyst, the syntheses of both random and alternating α,ω-dihydroxy MBCs were conducted by using the coupling chemistry of α,ω-dihydroxy compounds. This dehydration synthesis between the two terminal hydroxyl groups not only ensures the successful preparation of MBCs, but also can guarantee to form α,ω-dihydroxy polymers. At the same time, the preparation of a hydroxyl terminated polystyrene-b-polybutadiene- b-polystyrene triblock copolymer (SBS) with high cis-1, 4 content via a novel nickel catalyst, [η3-Ni(CH2CHCHCH2OOCH3)][BPhF4] was also revealed. FT-IR, 1H-NMR, and 13C NMR indicated that the polybutadiene segment of the copolymer contains greater than 90% cis-1, 4 structure indicating achievement of this research goal. Toward the functionalization purpose, the results indicated that hydroxyl groups were successfully introduced into the terminals of the triblock copolymer (HO–SBS–OH).