Catalytic-reactions of living polymers: Density functional study of reactivity of phenol and phenoxides with the cyclic tetramer of polycarbonate

The reactivity of phenol, lithium phenoxide (LiOPh), and sodium phenoxide ( NaOPh) with the cyclic tetramer of bisphenol A polycarbonate (BPA-PC) has b een investigated using density functional calculations. The potential energ y of the system is computed using a suitable reaction coordinate and relaxi ng all other degrees of freedom by Car-Parrinello molecular dynamics. Both LiOPh and NaOPh catalyze ring opening with small energy barriers (Delta E 4 .0, 2.5 kcal/mol, respectively) to a chain with a phenyl carbonate at one e nd and a phenoxide at the other, a "living polymer". The barrier is large f or phenol (Delta E > 40 kcal/mol), but the total energy differences between the reactants and the chain are very small in all three molecules. We disc uss the balance between changes in entropy and energy, and we compute the v ibrational properties of metastable intermediate species.