Computer simulation of the aggregation of ion pairs in the polymerization of styrene initiated by RCl/SnCl4/NRCl− systems

✍ Scribed by Ryszard Szymanski; Krzysztof Matyjaszewski

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 487 KB
• Volume: 4
• Category: Article
• ISSN: 1022-1344
• DOI: 10.1002/mats.1995.040040208

✦ Synopsis

Abstract

Computer simulations show that ion pair aggregation can be responsible for the unusual dependence of the initial rate of polymerization on the concentration of added salt in the cationic polymerization of styrene initiated by RCl/SnCl~4~/NRCl^−^. Addition of small amounts of tetraalkylammonium chloride to the system reduces the rate of polymerization due to the decrease of the concentration of propagating free cations. Subsequent salt addition leads to a small rate increase, and then the rate decreases at higher [salt]~0~/[SnCl~4~]~0~ ratio. The simulations show that the rate increase can be ascribed to the formation of aggregates of ion pairs and thus to a higher overall proportion of carbocations resulting in faster polymerization. The decrease of the polymerization rate at higher concentrations of added salt can be explained by the conversion of free SnCl~4~ to SnCl anions which are weaker Lewis acids. The effect of various equilibrium constants on the total concentration of carbocations as a function of added salt is simulated.