EFFECTS OF ACRYLIC-ACID ON NUMBER DENSITY OF POLYMER PARTICLES IN EMULSIFIER-FREE EMULSION COPOLYMERIZATION OF STYRENE AND ACRYLIC-ACID

An end-chain extension model for number density of polymer particles i s derived in this work. This model shows that the logarithmic value of the number density of polymer particles is proportional to the concen tration of acrylic acid in aqueous solution in emulsifier-free emulsio n copolymerization of styrene and acrylic acid. The end chains on poly mer particles are composed of acrylic acid segments from nucleating ol igomers and radicals absorbed by polymer particles. The end chains of hydrophilic segments extend into aqueous solution with surface charge at their terminals. This effect lowers the capture radical ability of polymer particles and increases the number density of polymer particle s. The experimental results confirm the extension model with the conte nt of acrylic acid ranging from 1.156 to 5.064 gl(-1) at 80 degrees C.