220 ml of methylene chloride are added to a solution, rendered inert with nitrogen, of 8.088 g (0.04 mol.) of 4,4′-dihydroxydiphenyl ether and 1.826 g (0.01 mol.) of 4,4′-dihydroxybiphenyl (DOD) as well as 4.4 g (0.111 mol.) of sodium hydroxide in 220 ml of water. In a one-step procedure, 0.263 g (0.00175 mol. or 3.5 mol. % relative to bisphenol) of p-tert.-butylphenol (BUP) are added as chain terminator. At a pH value of 14 and at room temperature, 6.9 ml (9.88 g, 0.099 mol.) of phosgene are added in the course of 10 minutes. In order to prevent the pH value from falling below 12, 25% sodium hydroxide solution was added during the phosgenation. When the phosgenation is complete, and after rinsing with nitrogen, 0.07 ml (0.0005 mol., 1 mol. % relative to bisphenol) of n-ethylpiperidine is added as catalyst, and stirring is then carried out for one hour. The aqueous phase is separated off, and the organic phase is acidified with phosphoric acid and washed with distilled water until neutral and free of salt. Precipitation of the polymer in methanol and drying yield 8.55 g of polycarbonate.
