Polymerization of Methacrylic Acid with Potassium Peroxodisulfate in Aqueous Solution

Polymerization of Methacrylic Acid with Potassium Peroxodisulfate in Aqueous Solution 

Safety precautions More this experiment is carried out, Sect. 2.2.5 must be read as well as the material safety data sheets (MSDS) for all chemicals and products used. 

11 ml of distilled water are heated to 80 °C in a 50-ml standard apparatus (round-bottom flask, several inlets for stirrer, reflux condenser, nitrogen flux or vaccum, thermometer, heating bath) with two dropping funnels. At this temperature 6 g (0.07 mol) of methacrylic acid, purified by vacuum distillation under nitrogen, and a solution of 0.18 g (0.66 mmol) of potassium peroxodisulfate in 4 ml of water are slowly introduced dropwise into the flask over a period of 10-15 min, while stirring with a magnetic stirrer. The methacrylic acid polymerizes immediately, as may be seen from the increased viscosity of the solution. After the additions are complete, the temperature is held for another hour at 80 °C. 

After polymerization the rather viscous solution is added dropwise to 50 ml of 0.1 N HCI, whereupon the polymer precipitates.The polymer is filtered, if necessary broken up, extracted in a Soxhiet apparatus with petroleum ether for 5 h, and finally dried to constant weight in vacuum at 50 °C.The yield is quantitative. 

Poly(methacrylic acid) is soluble in water, methanol, 1,4-dioxane, and DMF.The solution viscosity of the polymer is measured in water at 20 °C, using concentrations of 0.5, 0.7,1.0,1.5,2.0,2.5,3.0,3.5, and 4.0 g/l (Ostwald viscometer, capillary diameter 0.3 mm). A plot of risp/c against c gives a curve that is typical of polyelectrolytes (see Sects. 1.3.1.2 and 2.3.3.3.1). 

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