Azobisisobutyronitrile in a Dilatometer

Example 3.6 Bulk Polymerization of Styrene with 2,2 -Azobisisobutyronitrile in a Dilatometer 

Safety precautions Before 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. 

K is a constant that can be calculated from the specific volumes of the monomer and polymer at the appropriate temperature. One can, however, also determine the relationship between U and At/ by direct experiment. 

The following amounts of 2,2 -azobisisobutyronitrile (AIBN) are weighed into 4 graduated 25-ml flasks 35, 110, 180, and 250 mg (0. 21, 0.67, 1.10, and 1.52 mmol). The flasks are filled to the mark with destabilized styrene (at 20°C) and the amount of styrene divided by 25 ml gives the density at 20°C (neglecting the partial volume of AIBN). 

The dilatometers are emptied as follows. The dilatometer, cooled in ice to below 10°C, is inclined carefully over a small beaker, the capillary is lifted from the dilatometer, the polymer solution poured into a beaker and the capillary and dilatometer bulb washed out several times with small amounts of toluene. The polymer solutions are each added dropwise to an 8- to 10-fold excess of methanol. The amounts of polymers precipitated are determined gravimetricaUy. 

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