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
We have reported the synthesis, morphological structure and single crystal structure of crystalline syndiotactic 1,2-polybutadiene. Now we want to study the effect of self-seeding nucleation on the crystallization beh...We have reported the synthesis, morphological structure and single crystal structure of crystalline syndiotactic 1,2-polybutadiene. Now we want to study the effect of self-seeding nucleation on the crystallization behavior of it. In the report, the effects of self-seeding nucleation the crystallization behavior of syndiotactic 1,2-polybutadiene were studied by DSC and PLM techniques. The results indicated that the crystallization temperature of crystalline syndiotactic 1,2-polybutadiene increased obviously and the spherulite size decreased markedly after the process of self-seeding nucleation treatment.展开更多
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..
文摘We have reported the synthesis, morphological structure and single crystal structure of crystalline syndiotactic 1,2-polybutadiene. Now we want to study the effect of self-seeding nucleation on the crystallization behavior of it. In the report, the effects of self-seeding nucleation the crystallization behavior of syndiotactic 1,2-polybutadiene were studied by DSC and PLM techniques. The results indicated that the crystallization temperature of crystalline syndiotactic 1,2-polybutadiene increased obviously and the spherulite size decreased markedly after the process of self-seeding nucleation treatment.
