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Abstract
The copolymerization of styrene (S) and acrylonitrile (AN) in the presence of ethylaluminum sesquichloride (EASC) results in alternating copolymers except when styrene is present in considerable excess in the initial monomer feed. The molecular weight of the copolymer is highest at an equimolar monomer feed. When the concentration of EASC and the S/AN mole ratio are kept constant and the total monomer concentration is increased, the polymerization rate increases and passes through a maximum at a 2:2:1 S/AN/EASC mole ratio but the molecular weight increases and attains a limiting value. The rate of polymerization is proportional to the concentration of EASC. When the concentration of either monomer and the EASC concentration are kept constant and the concentration of the other monomer is varied, the polymerization rate passes through a maximum at an equimolar ratio, irrespective of which monomer is varied. The molecular weights of the copolymers are unchanged with conversion when the EASC concentration is low but, at a higher EASC concentration, the molecular weight decreases with conversion and attains a limiting value.