Effects of acrylic acid on radical penetration length and conversion in emulsifier-free emulsion copolymerization of styrene and acrylic acid

A changeable radical penetration length model is presented in this work for emulsifier-free emulsion copolymerization of styrene and acrylic acid. Radical penetration length in polymer particles varies with the content of acrylic acid. When monomer droplets are present, the radical penetration length is proportional to the number density of polymer particles in solution at the stage of shell region polymerization. However, the radical penetration length keeps constant at this stage in a batch reaction. The 2/3 power of conversion is proportional to the reaction time and 2/3 power of the number density of polymer particles. When the content of acrylic acid is 1.156 to 5.064 gl(-1) under our experimental conditions, the logarithmic value of the slope obtained from 2/3 power of conversion versus reaction time is proportional to the concentration of acrylic acid in aqueous solution.