SOME OBSERVATIONS IN THE AQUEOUS POLYMERIZATIONS OF METHYL-METHACRYLATE (MMA) INITIATED BY THE REDOX SYSTEMS FE2-S2O82- AND FE2+-H2O2()

It has been observed in the aqueous polymerizations of methyl methacry late (MMA) initiated by the redox system, ferrous ammonium sulphate (F AS)-potassium persulphate (KPS), that at 10 degrees C or below, the se parating polymer phase is always a milky white precipitate remained su spended in the aqueous phase, while above 20 degrees C, the polymer ph ase is a stable colloid and is yellow in colour (light or deep, depend ing on the concentration of the reactants, 10(-5) to 10(-3) mol/dm(3)) . The colloid stability of the latex solutions increases with the rise in temperature in the range 20 to 50 degrees C. Between 10 to 20 degr ees C, the separating polymer phase is partly colloidal and partly coa rse precipitate. If the polymerization is initiated by the Fenton's re agent (Fe2+-H2O2), under identical experimental conditions,the polymer phase is always a precipitate in the temperature range 4 to 50 degree s C. At or below 10 degrees C, the latex particles are milky white, bu t above 10 degrees C the particles are yellowish. It is suggested that the complex ions [Fe(H2O)(5)OH](2+), [Fe(H2O)(4)(OH)(2)](+) and [Fe(H 2O)(4)(OH)(2)(H2O)(4)Fe](4+), produced in the systems during the react ions (depending on temperature and pH of the solution), are strongly a dsorbed by the polymer molecules (PMMA)/latex particles, having sulpha te (-0-SO3-) end groups (polymer from the KPS-MMA-FAS system), through the electrostatic interactions, and act as peptisers to the lyophobic polymer colloids. In the Fe2+-MMA-H2O2 system, the polymers having ne utral OH end groups, do not adsorb strongly the positively charged fer ric ion complexes. The purified polymers (PMMA) are found to contain i ron.