TEMPO-controlled radical suspension polymerization of poly(styrene)-block-poly(styrene-co-acrylonitrile) and poly(styrene)-block-poly(styrene-co-butylmethacrylate)

Suspension polymerization expands the study of controlled radical polymeriz ation to high conversions and is known as a method to synthesize polymers w ith high molecular weights. The radical block copolymerizations of styrene (S) and acrylonitrile (AN) or butyl methacrylate (BUMA) controlled by 2,2,6 ,6-tetramethylpiperidine-N-oxyl (TEMPO) was performed in an oil/water press ure reactor system at a temperature of 125 degrees C. TEMPO-terminated styr ene homopolymer was employed as macroinitiator. The systems were examined b y varying the composition of the monomer mixture at a constant reaction tim e, as well as by varying the reaction time for a characteristic monomer com position to get all of the possible conversion range. The solubility effect s of acrylonitrile in the suspension medium were considered, Furthermore, t he yield of the reaction was improved through initiator addition by taking control of the reaction. The polymerizations could proceed under control up to a conversion of 80-90%. By using the copolymerization equations, the so lubility of pure acrylonitrile in the suspension medium could be calculated and was found to be 8 wt.%.