Living cationic polymerization of p-methoxystyrene by hydrogen iodide/zinc iodide at room temperature

Summary Cationic polymerization of p-methoxystyrene initiated by HI/ZnI₂ in toluene afforded living polymers not only at low temperature (–15°C) but at room temperature (+25°C) as well. The number-average molecular weight of the polymers was directly proportional to monomer conversion and in excellent agreement with the calculated value assuming that one polymer chain forms per unit hydrogen iodide. On addition of a fresh feed of monomer at the end of the first-stage polymerization, the added feed was smoothly polymerized at nearly the same rate as in the first stage; the polymer molecular weight further increased in direct proportion to monomer conversion and was close to the calculated value for living polymer. Throughout these reactions, the molecular weight distribution of the polymers stayed very narrow (¯M_w/¯M_n<1.1). This is the first example of living cationic polymerizations of styrene derivatives that proceed even at room temperature.