Polymerization of aromatic nuclei. VIII. Molecular weight control in benzene polymerization

The molecular weight of p ‐polyphenyl prepared from benzene—aluminum chloride—cupric chloride, was affected by solvent, concentration, and temperature. Relative molecular weights were measured by polymer solubility in chloroform, and positions of the infrared para band and ultraviolet reflectance λ max . The order of effectiveness of the solvents in reducing molecular weight was: o ‐C 6 H 4 Cl 2 > 1,2,4‐C 6 H 3 Cl 3 > SnCl 4 ∼ CS 2 > [C 6 H 6 ]. Degradative oxidation revealed that o ‐dichlorobenzene solvent was incorporated as an endgroup to only a minor extent. In general, the molecular weight of p ‐polyphenyl decreased with increasing temperature and with decreasing concentration. The theoretical aspects are treated.