Cationic polymerization of isobutyl vinyl ether (IBVE) was investigated using Schreiner's thiourea (STU) combined with Im-TEPB bearing a 2-iodoimidazolium cation and a noncoordinating borate anion. Both the CF 3 CO 2 H adduct and the HCl adduct of IBVE had the ability to initiate polymerization, but the number-averaged molecular weight was rather low compared with the theoretical value and the molecular weight distribution was fairly broad (M w /M n > 2.6). On the other hand, fast cationic polymerization of p-methoxystyrene (pMOS, 50 equiv relative to pMOS•HCl) proceeded using STU/Im-TEPB cocatalysts, giving rise to poly(pMOS) with M n = 4580 and M w /M n = 1.38. STU/Im-TfO exhibited decreased activity due to the coordination of a trifluoromethanesulfonate counteranion with the NH group of STU, which was supported by the NMR spectrum, DFT calculation, and UV−vis titration experiment. The molecular weight of poly(pMOS) could be roughly regulated by STU/Im-TEPB cocatalysis between M n = 2400 and M n = 7500 by the monomer feed ratio with keeping the molecular weight distribution below 1.41, although these values were lower than the theoretical ones probably due to the unignorable chain-transfer reaction. The polymerization kinetics revealed that the monomer consumption rate depends on the concentration of Im-TEPB rather than STU, which reveals the catalytic function of STU/Im-TEPB.

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 M n = 6930 and M w/M n = 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.

The cationic polymerization of p‐methoxystyrene (pMOS) was carried out at 25°C using pMOS·HCl and Sb(C6F5)3. Under the condition of [pMOS·HCl]:[Sb(C6F5)3]:[pMOS] = 10:10:500 in mM concentration, the polymerization in CH3CN/CH2Cl2 (3/1 in volume ratio) homogeneously proceeded giving rise to poly(pMOS) with Mn = 5800 and Mw/Mn = 1.50. Based on the monomer consumption rate, the catalytic activity was increased in the order of Sb(C6F5)3 (5.9 × 10−1 h−1) > Te(C6F5)2 (2.0 × 10−1 h−1) > IC6F5 (1.0 × 10−2 h−1). In the presence of nBu4NCl (0.02 equivalent relative to Sb(C6F5)3), the molecular weight distribution became narrower (Mw/Mn = 1.23), but the MALDI‐TOF/MS implied chain transfer reactions. On the other hand, the cationic polymerization of pMOS in CH2Cl2 using [MeSbPh3][TEPB] combined with nBu4NCl resulted in better molecular weight controllability (calculated Mn = 6100 and theoretical Mn = 6300), where chain transfer reactions were decreased as confirmed by the MALDI‐TOF/MS analysis. [SbPh4][TEPB] and [SbPh4][OTf] exhibited a decreased catalytic activity. [EtOCOCH2SbPh3][TEPB] with the electron‐withdrawing ester group showed the highest activity (monomer conversion reached 91% in 8 h) while maintaining narrow molecular weight distribution (Mw/Mn = 1.27). p‐Methylstyrene and styrene were also polymerized using catalyst [EtOCOCH2SbPh3][TEPB], although the polymerization was not controlled.