Pnictogen bonding‐mediated controlled cationic polymerization of styrene derivatives: Catalytic activity investigation using non‐ionic and ionic pnictogen compounds

Abstract

AbstractThe 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.