Hyperbranched aryl polycarbonates derived from A(2)B monomers versus AB(2) monomers
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abstract
Hyperbranched aryl polycarbonates were prepared via the polymerizations of A2B and AB2 monomers, which involved the condensation of chloroformate (A) functionalities with tert-butyldimethylsilyl-protected phenols (B), facilitated by reactions with silver fluoride. The polymerization of the A2B monomer gave hyperbranched polycarbonates bearing fluoroformate chain ends, which were hydrolyzed to phenolic chain-end moieties and further elaborated to tert-butyldimethylsilyl ether groups. The polymerization of the AB2 monomer gave tert-butyldimethylsilyl ether-terminated hyperbranched polycarbonates. The polymerizations were conducted at 23-70 C in 20% acetonitrile/tetrahydrofuran in the presence of a stoichiometric excess of silver fluoride for 20-40 h to afford hyperbranched polycarbonates with weight-average molecular weights exceeding 100,000 Da and polydispersity indices of typically 2-3. The degrees of branching were determined by a reductive degradation procedure followed by high-performance liquid chromatography. Alternatively, the degrees of branching were measurable by solution-state 1H NMR analyses and agreed with the statistical 50% branching expected for the polymerization of A2B and AB2 monomers not experiencing constructive or destructive electronic effects on the reactivity of the multiple functional groups. 2002 Wiley Periodicals, Inc. J. Polym. Sci. Part A: Polym. Chem.
