Herman O. Krabbenhoft

Two‐component initiator systems for the ring‐opening polymerization of oligomeric cyclic bisphenol‐A carbonates: The in situ cleavage of disulfides by triarlyphosphines

A two-component initiator system based on the in situ cleavage of phenyl disulfide by a triarylphosphine has been developed for the ring-opening polymerization of cyclic bisphenol-A (BPA) carbonate oligomers. This development has potential use in composite applications such that the prepolymer can suitably wet the composite material before being converted to high-molecular-weight polymer. The initiator precursors (phenyl disulfide and triphenylphosphine) do not independently initiate significant ring-opening polymerization of the oligomeric cyclic BPA carbonate mixture. A mixture of cyclic BPA carbonate oligomers and one of the initiator components (phenyl disulfide), combined and heated at 300°C with a mixture of the cyclics and the other initiator component (triphenylphosphine), does produce a high-molecular-weight polymer (Mw = ∼ 70,000). The polymerization-initiating species is thought to be thiophenyltriphenylphosphonium thiophenoxide. The effects of concentration of the initiator components, reaction temperature, time, and so forth on polymerization were studied; in general, the degree of polymerization ranged from about 65 to 75%.

Two‐Component initiator systems for the ring‐opening polymerization of oligomeric cyclic bisphenol‐A carbonates. Studies with in situ generated wittig salts

A two-component initiator system based on the in situ generation of Wittig salts (alkytriarylphosphonium bromides) has been developed for the ring-opening polymerization of cyclic bisphenol-A (BPA) carbonate oligomers for potential use in composite applications so that the prepolymer can suitably wet the composite material before being converted to high molecular weight polymer. The Wittig salt precursors (an alkyl bromide, such as hexadecyl bromide, and a triarylphosphine, such as triphenylphosphine) did not independently initiate significant ring-opening polymerization of the oligomeric cyclic BPA carbonate mixture. However, when the two mixtures of cyclic BPA carbonate oligomers and initiator component were combined, a high molecular weight polymer (M w = ∼65,000) was produced. The polymerization initiating species is thought to be hexadecyltriphenyl-phosphonium bromide. Consistent with this hypothesis is the observation that authentic Wittig salts did initiate ring-opening polymerization to provide high molecular weight polycarbonate. The effects of structure and concentration of the initiator components, reaction temperature, time, etc. on polymerization were studied ; in general, the degree of polymerization ranged from 65 to 85%.