Macrocycles, 22

Abstract

AbstractThe phosgenation of bisphenol A with diphosgene in the CH2Cl2/NaOH system was studied using the pseudo‐high‐dilution method either with triethylamine, with triethylbenzyl ammonium chloride (TEBA‐Cl), or with tetraphenylphosphonium chloride as catalyst. For Ph4PCl, only low‐molecular‐weight polycarbonates containing various by‐products were obtained. With the TEBA catalyst, the fraction of cycles and the average molecular weights increased with higher feed ratios of the catalyst. Both the fraction of cycles and the molecular weights steeply decreased at higher temperatures. With triethylamine as catalyst both the fraction of cycles and molecular weight passed through a maximum at low catalyst concentration, when the feed ratio of triethylamine was varied. Higher temperatures favored slightly lower fractions of cycles and lower molecular weights. Samples containing ≥ 95 mol‐% of cycles were obtained. The cycles were identified by matrix‐assisted laser desorption ionization time‐of‐flight (MALDI‐TOF) mass spectrometry up to 22 000 Da in the case of virgin samples, and up to 55 000 Da after fractionation by size exclusion chromatography (SEC). Selected samples were characterized by SEC measurements and evaluated by the triple‐detection method. High polydispersities and a tendency towards a bimodal mass distribution were found, when triethylamine was used as catalyst.MALDI‐TOF mass spectrum of a polycarbonate prepared by triethylamine‐catalyzed phosgenation at 20 °C by the pseudo‐high‐dilution method.magnified imageMALDI‐TOF mass spectrum of a polycarbonate prepared by triethylamine‐catalyzed phosgenation at 20 °C by the pseudo‐high‐dilution method.