Controlled/living cationic polymerization of styrene with BF3OEt2 as a coinitiator in the presence of water: Improvements and limitations

The controlled/living cationic polymerization of styrene using R–OH/BF3OEt2 (R–OH = 1-phenylethanol (1), 2-phenyl-2-propanol (2) and 1-(4-methoxyphenyl)ethanol (3)) at 0 °C in CH2Cl2 and in the presence of water was investigated. With 1/BF3OEt2, the poor control over molecular weight and molecular weight distribution was ascribed to a competitive protonic initiation induced by water. The molecular weight of the polymers obtained with 2/BF3OEt2 and 3/BF3OEt2 at low water content ([H2O] ⩽ 0.11 M) increased in direct proportion to the monomer conversion in agreement with the calculated values, assuming that one initiator molecule generates one polymer chain, but the molecular weight distribution was found relatively broad (Mw/Mn ∼ 1.8). 1H NMR analyses confirmed that polymerization proceeds via reversible activation of C–OH terminus, but some loss of hydroxyl functionality was revealed. Some trials using high water contents in the recipe ([H2O] ⩾ 1.6 M) produced only traces of polymer due to catalyst decomposition.