Kinetic Studies of the Solution Polymerization of Trioxane Catalyzed by BF3·O(C2H5)2. VI. The Catalytic Mechanism of Boron Trifluoride Coordination Complexes in Ethylene Dichloride

Abstract

The initiation mechanism in the cationic polymerization of trioxane by the BF3 coordination complex catalyst was studied in ethylene dichloride at 30°C. The coordination complexes of BF3 with diethyl ether (Et2O), ethyl alcohol (EtOH) and acetic acid (AcOH) were used as catalysts. Under similar conditions, the rates of polymerization decreased in the order: BF3·EtOH>BF3·AcOH>BF3·Et2O, whereas the molecular weights of the polymers decreased in the order: BF3·Et2O>BF3·EtOH\simeqBF3·AcOH. The molecular weight of the polymer formed was unaffected by the addition of the same compound as the donor molecule in the BF3 coordination complex. However, on the addition of EtOH to the polymerization system catalyzed by BF3·Et2O, the rate of polymerization increased and the molecular weight of the polymer decreased. On the other hand, the addition of Et2O to the system catalyzed by BF3·EtOH decreased the rate of polymerization and increased the molecular weight of the polymer formed. The order of catalytic reactivity and the effect of the additive support the idea that the initiation reaction, is not an interaction of the BF3 molecule with trioxane but an addition of the cation produced from the BF3 coordination complex to the trioxane molecule.