Bai-Xiang Li

Ethylene polymerization by 2-iminopyridylnickel halide complexes: synthesis, characterization and catalytic influence of the benzhydryl group

A series of 2-(2-benzhydrylbenzenamino)pyridine ligands (L1–L13) was synthesized and used as bidentate N^N ligands with nickel halides to afford the corresponding nickel dihalide complexes L(2)Ni(2)Cl(4) C1–C13 and L(2)NiBr(2) D1–D13. All ligands and complexes were characterized by IR and NMR spectroscopy, and by elemental analysis. The molecular structures of the representative complexes C1·2CH(3)OH, C5·2H(2)O, D4, D7 and D9 were confirmed by single-crystal X-ray diffraction studies. Upon activation with either methylaluminoxane (MAO) or ethylaluminium sesquichloride (Et(3)Al(2)Cl(3), EASC), these nickel pre-catalysts exhibited high activities (up to the range of 10(7) g mol(-1) (Ni) h(-1)) towards ethylene polymerization, producing branched polyethylenes with narrow polydispersity.

CURRENT RESEARCH, KEY PERFORMANCES AND FUTURE DEVELOPMENT OF SEARCH AND RESCUE ROBOT

A survey of the research status for search and rescue robots in Japan,USA,China,and other countries is provided. According to current research,the experience,and the lessons learned from application,there are four key performances for search and rescue robot,which are,survivability,mobility, sensing,communicability,and operability.It is proved that, research of search and rescue robot is converted to practice from experiment gradually,Multi-technique fusion and multi-agent intelligent network are considered to be the future development requirement of the search and rescue robot.Dis- aster prevention,disaster reduction,and disaster rescue are important parts of the national public safety.And they are also crucial issues in the safety of citizens and their estates. Search and rescue robotic technique is an urgently needed, strategic,and core technique for national development.It will have important and strategic effect on the national economy and the national safety.

Synthesis, characterization and ethylene (co-)polymerization behavior of half-titanocene 2-(1-(arylimino)ethyl)quinolin-8-olate chlorides

The series of half-titanocene 2-(1-(arylimino)ethyl)quinolin-8-olate dichlorides, Cp′TiCl2L (Cp′ = η5-C5H5 or η5-C5Me5, L = 2-(1-(2,6-R1-4-R2-phenylimino)ethyl)quinolin-8-olate), was synthesized via the stoichiometric reaction of Cp′TiCl3 with the corresponding potassium salt, viz.2-(1-(2,6-R1-4-R2-phenylimino)ethyl)quinolin-8-olate. All compounds were characterized by elemental analysis, 1H and 13C NMR spectroscopy. The molecular structures of complexes C2 and C4 were determined by single-crystal X-ray diffraction. When activated with methylaluminoxane (MAO), all half-titanocene pre-catalysts exhibited high activities for ethylene polymerization and co-polymerization with α-olefins or norbornene.

Synthesis of Polyethylene Containing Allene Groups: A Simple and Efficient Route to Functional Polyethylene

Allene groups are first employed as the reactive moiety in the simple and efficient synthesis of well-defined functional polyethylene. By copolymerization of ethylene with allene group substituted norbornene, the allene group is successfully introduced into the polyethylene with a high content. The retained allene groups are demonstrated to be highly reactive in following photoinduced functionalized reactions and can be efficiently converted into the functional groups without the multi-step, time consuming processes that have generally been required in previous reports, providing the side group-functionalized polyethylene with a wide range of functional group content.

DEVELOPMENT OF A SHAPE-SHIFTING MOBILE ROBOT FOR URBAN SEARCH AND RESCUE

A portable shape-shifting mobile robot system named as Amoeba II (A-II) is developed for the urban search and rescue application.It is designed with three degrees of freedom and two tracked drive systems.This robot consists of two modular mobile units and a joint unit.The mobile unit is a tracked mechanism to enforce the propulsion of robot.And the joint unit can transform the robot shape to get high environment adaptation.A-If robot can not only adapt to the environment but also change its body shape according to the locus space.It behaves two work states including the linear state (named as I state) and the parallel state (named as II state).With the linear state the robot can climb upstairs and go through narrow space such as the pipe,cave,etc.The parallel state enables the robot with high mobility on rough ground.Also,the joint unit can propel the robot to roll in sidewise direction.Two modular A-II robots can be connected through jointing common interfaces on the joint unit to com...

Living syndiospecific polymerization of propylene with sterically encumbered titanium complexes activated by MMAO

A series of sterically encumbered (salicylaldiminato)(β-enaminoketonato)titanium complexes [3-tBu-2-OC6H3CHN(C6F5)][RNC(CF3)CHC(tBu)O]TiCl2 [1a: R = Ph, 1b: R = C6H4F(p), 1c: R = C6H4Cl(p), 1d: R = C6H4Br(p), 1e: R = C6H4Br(o)] were synthesized and tested to be efficient catalysts for syndiospecific polymerization of propylene in the presence of modified methylaluminoxane at room temperature. The introduction of a bulky bromine atom ortho to the imine nitrogen of the β-enaminoketonato ligand not only successfully improved the pentad syndiotacticity (rrrr) of the resulting polypropylenes from 88.5% to 97.2%, but also provided better protection of the active site from attack of free AlR3 or monomers and thus contributed to the living polymerization nature, while keeping high catalytic activity. More importantly, compared with the famous pentafluorinated FI-Ti/MAO catalyst system, the sterically congested complex 1e with the bromine atom ortho to a N-aryl group displayed almost two times higher catalytic activity (14.5 vs. 28.0 kg mol−1 h−1), producing polypropylenes with even higher pentad syndiotacticity (rrrr = 97.2% vs. 96.0%) and similar narrow molecular weight distributions (Mw/Mn = 1.12–1.26). In addition, the polymerization proceeded with a different monomer insertion mode of 1,2-insertion and a similar chain-end control mechanism. Quantitative 13C NMR spectra revealed that polymers with various stereo structures ranging from highly syndiotactic and regioregular to atactic and regio-irregular polymers at different reaction temperatures were achieved, and the probable formation routes were proposed. The percentage of regio-irregularities of the monomer sequence arising from 2,1-insertion and 3,1-enchainment increased with the rise of reaction temperature.

ANALYSIS OF TIPOVER STABILITY FOR NOVEL SHAPE SHIFTING MODULAR ROBOT

A novel three-module robot has been introduced. It can change its configuration to adapt to the uneven terrain and to improve its tipover stability. This three-module tracked robot has three kinds of symmetry configuration. They are line type, triangle type, and row type. After the factors and the countermeasures of mobile robots tipover problem are analyzed, stability pyramid and tipover stability index are proposed to globally determinate the mobile robots static stability and dynamic stability. The shape shifting robot is tested by this technique under the combined disturbance of pitch, roll and yaw in simulation. The simulation result shows that this technique is effective for the analysis of mobile robots tipover stability, especially for the reconfigurable or shape shifting modular robot. Experiments on three symmetry configurations are made under unstructured environments. The environment experiment shows the same result as that of the simulation that the triangle type config...