Living cationic polymerization of styrene by the 1-phenylethyl chloride/tin tetrachloride initiating system in the presence of tetra-n-butylammonium chloride

Summary

An initiating system, consisting of 1-phenylethyl chloride, tin tetrachloride, and tetra-n-butylammonium chloride [CH₃CH(Ph)C1/SnCl₄/nBu₄NCl], led to living cationic polymerization of styrene in CH₂Cl₂ solvent at-15°C; typically, CH₃CH(Ph)Cl/SnCl₄/nBu₄NCl=20/100/40 mM for 1.0 M of styrene. The living nature of the process was confirmed by an increase in the number-average molecular weight ($\bar M_n$) of the polymers in direct proportion to monomer conversion and its continuation on supplying a fresh feed of styrene after the polymerization; the observed $\bar M_n$ was close to the calculated value assuming that one molecule of CH₃CH(Ph)Cl yields one living polymer. Throughout these reactions, the polymer's molecular weight distribution (MWD) stayed very narrow ($\bar M_w /\bar M_n \leqslant 1.1$), though slightly broadening after the second monomer addition. In the absence of nBu₄NCl, the CH₃CH(Ph)Cl/SnCl₄ system yielded polystyrene with a bimodal MWD where the lower polymer fraction alone was apparently of a long lifetime. Styrene polymerization with the H₂O/SnCl₄ system was also examined, both with and without added nBu₄NCl, and a long-lived propagating species was obtained in the presence of nBu₄NCl.