Incorporation of halogen endgroups in polymers and their detection by the dye test

Abstract

The incorporation of halogen endgroups in polymers has been established in the following cases for polymerization of styrene, methyl methacrylate and methyl acrylate: (1) chain transfer with halogenated hydrocarbons (chloroform, benzyl chloride, bromoform, ethylene dibromide, octadecyl bromide, ethyl iodide, cetyl iodide); (2) copolymerization with suitable components (vinyl bromide, tetrachloroethylene, trichloroethylene); (3) use of halogen atoms as initiators, e.g. FeCl₃ (+h_v), FeBr₃ (+h_v), HCl (+h_v) and KBr + H₂O₂ (+h_v); (4) chemical transformation of a group already present in a polymer, e.g., conversion of hydroxyl endgroup to halogen endgroup by a usual method; addition of hydrogen bromide to double bond in polymers. The method of detection consists in converting a polymer with halogen endgroups to a quaternary pyridinium halide by refluxing with pyridine, a few drops of glycerol being added in the case of chlorine endgroup to facilitate the reaction. The converted quaternary halogen endgroup is detected independently by two tests developed in this laboratory: the dyeinteraction test with rhodamine 6GX conc. (Calco) dye and also the dye-partition test for cationic group with Bromophenol Blue or Disulfine Blue VN 150 as reagents.