In this study,a novel iron-based catalyst system,Fe(acac)3/(isocyanoimino)triptenylphosphorane(IITP)/AlR3,was employed for the synthesis of syndiotactic 1,2-polybutadiene in hexane.This catalyst system exhibits remark...In this study,a novel iron-based catalyst system,Fe(acac)3/(isocyanoimino)triptenylphosphorane(IITP)/AlR3,was employed for the synthesis of syndiotactic 1,2-polybutadiene in hexane.This catalyst system exhibits remarkably high catalytic activity,achieving a polymerization activity of 762 kgpolymer·molcatalyst^(-1)·h^(-1)at 50℃with a[BD]/[Fe]molar ratio of 20000.Furthermore,living polymerization characteristic were observed during the investigation of the polymerization kinetics of 1,3-butadiene polymerization.These characteristics were well demonstrated by a narrow molecular weight distribution(PDI≈2.0)of the resulting polybutadiene and a linear relationship between-ln(1-c)and polymerization time as well as number average molecular weight and polymer yield.The resultant polymer showed a 1,2-selectivity of approximately 76%and stereoregularity ranging from 62%to 73%(rrrr).Additionally,through kinetic studies on polymerization reaction,an apparent activation energy Ea value of this catalytic system was calculated to be 84.98 kJ·mol^(-1),which suggests that high polymerization temperature favors efficient polymerization.展开更多
The crystalline syndiotactic 1,2-polybutadiene was synthesized with a catalytic system consisting of iron acetylacetonate , triisobutylaluminum and diethyl phosphite (DEP), and its single crystal structure was studied...The crystalline syndiotactic 1,2-polybutadiene was synthesized with a catalytic system consisting of iron acetylacetonate , triisobutylaluminum and diethyl phosphite (DEP), and its single crystal structure was studied by transmission electron microscopy (TEM) and electron diffraction (ED) techniques. The polymer with melting point 179 ℃ was found to have 89.3% 1,2 content and 86.5% sydiotacticity based on 13C NMR measurement. The single crystals of the polymer were achieved by melt crystallization of the solution cast thin films at 150 ℃ for 2 h. Bright field electron micrograph shows that the single crystal exhibits a hexagonal prism shape with its long axis along the crystallographic b-axis, as revealed by the corresponding ED pattern. The strong (hk 0) reflections of the ED pattern indicate that the single crystal possesses a very good crystallographic orientation with the c-axis perpendicular to the film plane. According to the orthorhombic packing of the planar zigzag chains, all of the diffraction points can be indexed, and the unit cell parameters calculated from the ED result are a=1.102 nm and b=0.664 nm. In order to obtain the unit cell parameter c, α highly oriented thin film of the polymer was prepared with a special melt drawn technique. The TEM bright field image indicates that the melt drawn thin films contain highly oriented lamellae with their growing direction perpendicular to the drawing direction. The corresponding ED pattern reveals the molecular chains are highly oriented, with the c-axis parallel to the drawing direction. The unit cell parameter c is 0.513 nm, as calculated from the (hk 0) reflections.展开更多
The crystalline syndiotactic 1,2-polybutadiene was synthesized in a catalytic system consisting of iron acetylacetonate [Fe(acac) 3], triisobutylaluminum [Al(i-Bu) 3] and diethyl phosphite (DEP), and its morphological...The crystalline syndiotactic 1,2-polybutadiene was synthesized in a catalytic system consisting of iron acetylacetonate [Fe(acac) 3], triisobutylaluminum [Al(i-Bu) 3] and diethyl phosphite (DEP), and its morphological structure was investigated by transmission electron microscopy (TEM). The polymer with a melting point 179 ℃ was found to have 89.3% 1,2 polybutadiene and 86.5% syndiotacticity based on 13C NMR measurements. The bright field electron micrograph shows that the solution cast film of syndiotactic 1,2-polybutadiene consists of lamellae with lateral scale in micron size. It should be noted that the lamellae have no branching and they are almost parallel each other in localized areas. The lamellar growing direction is along b axis. Surprisingly, the electron diffraction pattern of the film only exhibits strong (hko) reflections, which indicate that the lamellae possess a single crystal-like orientation, i.e., with their c axis perpendicular to the film plane, while a and b axes in the film plane. According to the orthorhombic packing of plane zigzag chains, the cell parameters calculated from the electron diffraction pattern are a=1.102 nm, b=0.664 nm, respectively, which are completely consistent with the results reported by Natta et al..展开更多
基金This work was financially supported by the National Key R&D Program of China(No.2022YFB3704700).
文摘In this study,a novel iron-based catalyst system,Fe(acac)3/(isocyanoimino)triptenylphosphorane(IITP)/AlR3,was employed for the synthesis of syndiotactic 1,2-polybutadiene in hexane.This catalyst system exhibits remarkably high catalytic activity,achieving a polymerization activity of 762 kgpolymer·molcatalyst^(-1)·h^(-1)at 50℃with a[BD]/[Fe]molar ratio of 20000.Furthermore,living polymerization characteristic were observed during the investigation of the polymerization kinetics of 1,3-butadiene polymerization.These characteristics were well demonstrated by a narrow molecular weight distribution(PDI≈2.0)of the resulting polybutadiene and a linear relationship between-ln(1-c)and polymerization time as well as number average molecular weight and polymer yield.The resultant polymer showed a 1,2-selectivity of approximately 76%and stereoregularity ranging from 62%to 73%(rrrr).Additionally,through kinetic studies on polymerization reaction,an apparent activation energy Ea value of this catalytic system was calculated to be 84.98 kJ·mol^(-1),which suggests that high polymerization temperature favors efficient polymerization.
文摘The crystalline syndiotactic 1,2-polybutadiene was synthesized with a catalytic system consisting of iron acetylacetonate , triisobutylaluminum and diethyl phosphite (DEP), and its single crystal structure was studied by transmission electron microscopy (TEM) and electron diffraction (ED) techniques. The polymer with melting point 179 ℃ was found to have 89.3% 1,2 content and 86.5% sydiotacticity based on 13C NMR measurement. The single crystals of the polymer were achieved by melt crystallization of the solution cast thin films at 150 ℃ for 2 h. Bright field electron micrograph shows that the single crystal exhibits a hexagonal prism shape with its long axis along the crystallographic b-axis, as revealed by the corresponding ED pattern. The strong (hk 0) reflections of the ED pattern indicate that the single crystal possesses a very good crystallographic orientation with the c-axis perpendicular to the film plane. According to the orthorhombic packing of the planar zigzag chains, all of the diffraction points can be indexed, and the unit cell parameters calculated from the ED result are a=1.102 nm and b=0.664 nm. In order to obtain the unit cell parameter c, α highly oriented thin film of the polymer was prepared with a special melt drawn technique. The TEM bright field image indicates that the melt drawn thin films contain highly oriented lamellae with their growing direction perpendicular to the drawing direction. The corresponding ED pattern reveals the molecular chains are highly oriented, with the c-axis parallel to the drawing direction. The unit cell parameter c is 0.513 nm, as calculated from the (hk 0) reflections.
文摘The crystalline syndiotactic 1,2-polybutadiene was synthesized in a catalytic system consisting of iron acetylacetonate [Fe(acac) 3], triisobutylaluminum [Al(i-Bu) 3] and diethyl phosphite (DEP), and its morphological structure was investigated by transmission electron microscopy (TEM). The polymer with a melting point 179 ℃ was found to have 89.3% 1,2 polybutadiene and 86.5% syndiotacticity based on 13C NMR measurements. The bright field electron micrograph shows that the solution cast film of syndiotactic 1,2-polybutadiene consists of lamellae with lateral scale in micron size. It should be noted that the lamellae have no branching and they are almost parallel each other in localized areas. The lamellar growing direction is along b axis. Surprisingly, the electron diffraction pattern of the film only exhibits strong (hko) reflections, which indicate that the lamellae possess a single crystal-like orientation, i.e., with their c axis perpendicular to the film plane, while a and b axes in the film plane. According to the orthorhombic packing of plane zigzag chains, the cell parameters calculated from the electron diffraction pattern are a=1.102 nm, b=0.664 nm, respectively, which are completely consistent with the results reported by Natta et al..
