PREPARATION AND RING-OPENING POLYMERIZATION OF CYCLIC OLIGOMERIC AROMATIC CARBONATES

The development of an efficient and convenient means for the preparation of aromatic cyclic oligomeric carbonates has made these materials available for a wide range of polymerization and processing studies. Mechanistic studies on the cyclization reaction have resulted in optimization such that 85-90% cyclics can be routinely prepared in interfacial reactions carried out at 0. 5 M final product concentration. The mixture of cyclic oligomers obtained from such reactions have a relatively low melting point, and are significantly less viscous than conventionally prepared polycarbonates. Anionic-initiated ring-opening polymerization leads to nearly complete conversion of the cyclics to high molecular weight linear polymer. Very high molecular weight polymers (> 200,000) with low dispersivities (M(w)BAR/M(n)BAR approximately 2.2) are obtained. The polymerization reaction shares many characteristics with other ring-opening polymerization reactions, with the notable exception that the reaction is driven by entropy rather than enthalpy, yet proceeds to 99.5% completion. The scope of the cyclic process, as well as potential applications are briefly discussed.