Controlled/Living Cationic Polymerization of <i>p</i>-Methoxystyrene Using Tellurium-Based Chalcogen Bonding Catalyst─Discovery of a New Water-Tolerant Lewis Acid Catalyst
Koji Takagi, Nao Sakakibara, Tomoki Hasegawa, Shuhei Hayashi
Abstract
The cationic polymerization of p-methoxystyrene (pMOS) was briefly investigated using TeOTe-TfO having the dicationic ditelluroxane structure as a chalcogen bonding (ChB) organocatalyst. With the HCl adduct of pMOS (pMOS·HCl) as an initiator, under appropriate conditions, the polymer molecular weight could be roughly controlled by the monomer feed ratio. We have subsequently performed the polymerization using the mononuclear telluronium cation TeMe-TfO as an organocatalyst and various alcohols as an initiator. For example, by using the H2O adduct of pMOS (pMOS·H2O) and under the condition of [pMOS·H2O]/[TeMe-TfO]/[pMOS] = 10:5:500 in mM concentration at 0 °C, poly(pMOS) with Mn = 6930 and Mw/Mn = 1.47 was obtained. Polymerizations with varying monomer feed ratios, monomer re-addition experiments, the careful analysis of the polymer chain ends by the 1H nuclear magnetic resonance (NMR) spectra, and polymerizations in the presence of water revealed that the cationic polymerization of pMOS proceeds in the living mechanism through the reversible activation of a carbon–hydroxy bond by the ChB interaction. By using the 125Te NMR spectra, it was confirmed that TeMe-TfO can be recovered without decomposition.