Catalytic Reactions of Living Polymers:  Density Functional Study of Reactivity of Phenol and Phenoxides with the Cyclic Tetramer of Polycarbonate

Abstract

The reactivity of phenol, lithium phenoxide (LiOPh), and sodium phenoxide (NaOPh) with the cyclic tetramer of bisphenol A polycarbonate (BPA-PC) has been investigated using density functional calculations. The potential energy of the system is computed using a suitable reaction coordinate and relaxing all other degrees of freedom by Car-Parrinello molecular dynamics. Both LiOPh and NaOPh catalyze ring opening with small energy barriers (∆E ) 4.0, 2.5 kcal/mol, respectively) to a chain with a phenyl carbonate at one end and a phenoxide at the other, a "living polymer". The barrier is large for phenol (∆E > 40 kcal/mol), but the total energy differences between the reactants and the chain are very small in all three molecules. We discuss the balance between changes in entropy and energy, and we compute the vibrational properties of metastable intermediate species.

Ring-Opening and Branching in Polycarbonates: A Density Functional-Monte Carlo Study

“…I. 9 An attack involving the (positively charged) metal atom is most likely at the carbonate group, as confirmed by experimental studies on a number of functionalized bisphenols using a variety of catalysts. 10 Therefore, we have performed a constrained simulation using the distance Rc between the carbonyl C and the reactant Ο as the initial reaction coordinate.…”

“…shows six snapshots of the trajectory for the reaction of LiOPh ap proaching from outside the cyclic tetramer 9. The reactants interact weakly for Rc ~ 4, with steric hindrances from neighboring phenyl rings giving rise to an energy barrier of 4 kcal/mol at Rc = 3.8 Â.…”

General and Theoretical Aspects of Phenols

“…The latter can be used for the photometric detection of phenol as in the case of diazotized 4-nitroaniline. Salicylic acid (2-hydroxybenzoic acid) can be produced by the Kolbe-Schmitt reaction 26 (studied by the density functional method 27 ) from sodium phenolate and carbon dioxide, whereas potassium phenolate gives the para compound. Alkylation and acylation of phenol can be carried out with aluminium chloride as catalyst; methyl groups can also be introduced by the Mannich reaction.…”

“…Adapted from Reference 220 with permission to Subsection III.A, we can estimate its energy of formation as the energy difference between the cis ortho-and trans ortho-CPs which, at the present computational level, is 10.0 kJ mol −1 after including ZPVE corrections. It is worthwhile to deduce the order of stability of cyanophenols similar to that given in equation 12 (27) It shows that, energetically, all cyanophenols fall into the interval of stability between the cis ortho-and trans ortho-CPs. Some characteristic vibrational modes are collected in Table 25 accompanied by their assignments based on the PEDs.…”

Branching Reactions in Polycarbonate: A Density Functional Study

“…The carboxylic branching structure observed in reactive pyrolysis in MM-PC production 3 indicated that the PC chain is most susceptible to branching at the carbonate group, where transesterification occurs in PC synthesis. [4][5][6] In some cases branching is desired, because longchain branched PC modifications show special shear viscosity behavior that makes them suitable for blow molding applications. The degree of branching can be controlled by branching agents such as THPE [1,1,1-tris(p-hydroxyphenol)ethane] 7 and polyphenols.…”