Morphology of poly-p-phenylene formed during the polymerization of benzene by molybdenum pentachloride or ferric chloride

The morphology of poly-p-phenylene(PPh) formed during the polymerization of benzene by molybdenum pentaehloride(MoCl5) or ferric chloride(FeCl3) has been studied. It has been found that well-developed fibrillar structures are formed during the polymerization by MoCl5. Electron diffraction confirms that the molecular axes of PPh are oriented parallel to the fibril axis. These fibrillar structures suggest that the nascent PPh possesses a predominantly para structure. It is thought that the fibrillar structures result from simultaneous polymerization and crystallization. The reflections in electron diffraction patterns can be indexed by assuming a monoclinic unit cell with dimensions a = 7.78 Å, b = 5.62 Å, c = 4.26 Å, (fiber axis), and β = 79%. It can be assumed that the most likely space group is P21a. Aggregates of many crystalline fragments with an indefinite shape were formed during the polymerization by FeCl3. They give electron or x-ray diffraction pattern having broad Debye rings. It is thought that subsequent reaction of the polymer with benzene to form polyphenyl side chains or polynuclear structures occurs much more frequently during the polymerization by FeCl3. These side reactions may prevent the formation of the fibrillar structures with higher crystallinity.