Formation of hydroxyl endgroups in polymers and their detection by dye tests

Abstract

The following possibilities of introducing hydroxyl endgroups in polymers have been experimentally realized: (1) redox initiation by ferrous sulfate + H₂O₂ (Fenton's reagent), N₂H₄, H₂O + H₂O₂, FeCl₃ + H₂O₂; photoinitiation by Fe(OH)⁺⁺ + light, H₂O₂ + ultraviolet light or sunlight, and initiation by unstable Ag⁺⁺⁺ complex in dark; (2) copolymerization with a trace of allyl alcohol or with traces of vinyl acetate and allyl acetate and subsequent hydrolysis; (3) chain transfer with butyl alcohols. The method of detection consists in first converting hydroxyl endgroups to carboxyl endgroups by refluxing with phthalic anhydride or 3-nitrophthalic anhydride in benzene and pyridine medium or with maleic anhydride in benzene medium and testing the resulting polymer for carboxyl endgroup by the dye-interaction test with rhodamine 6GX dye extract. The hydroxyl endgroup was also quickly converted to a strong acid endgroup like OSO₃H by reacting the polymer with chlorosulfonic acid in chloroform medium under controlled conditions and tested by the dye-interaction test or a dye-partition test with methylene blue. This test is not entirely satisfactory, as the reagent attacks the thermal polymers slightly.