Synthesis of end‐functionalized polystyrenes with organosilicon end‐capping reagents via living cationic polymerization

The end‐functionalization of living polymers with bases (methanol, benzylamine, diethyl sodiomalonate, and sodium methoxide) and organosilicon compounds [X  Si(CH3)3;X : CH2C(CH3)COO, CH3COO, CH2CHCH2, C6H5] was investigated in the living cationic polymerization of styrene initiated with the 1‐phenylethyl chloride/SnCl4/nBu4NCl system in CH2Cl2 at −15°C. The four bases and C6H5SiMe3, independent of their structures, were apparently incapable of reacting with the living end and invariably led to polystyrenes with the ω‐end chlorine [∼ ∼ ∼ CH2CH(Ph)Cl] originated from the initiating system. The number‐average end‐functionality (F̄n) of the chloride, determined by 1H‐NMR, was close to unity (F̄n > 0.9). The presence of chlorine in the polymer was also confirmed by elemental analysis. In contrast, the quenching by the trimethylsilyl compounds with X = methacryloxy, acetoxy, and allyl gave ω‐end‐functionalized polystyrenes with the corresponding terminal groups (X) for which the F̄n values were close to unity (F̄n > 0.9). The effects of the structure of silyl compounds on end‐capping are also discussed.