The molecular weight of polycarbonate formed by the carbonate‐ester interchange reaction of bisphenol‐A diacetate (BPAC2) and dimethyl carbonate (DMC) was found to depend on the composition of the oligomer formed in its first stage. At a [DMC] : [BPAC2] ratio of 2, an oligomer with relatively higher acetate end group concentration was formed. This upon further polycondensation yielded a polycarbonate of inherent viscosity, 0.2‐0.25 dL/g. Upon addition of DMC at a later stage in the oligomer‐forming reaction, an oligomer containing relatively higher carbonate end groups could be obtained. These oligomers gave polycarbonates higher inherent viscosity, 0.4‐0.5 dL/g. It is therefore proposed that oligomers having carbonate end groups are more reactive in self‐polycondensation than those containing acetate end groups. © 1995 John Wiley & Sons, Inc.

SynopsisChanges in degree of polymerization (DP) of cellulose during the viscose process were investigated by determining the number aver%e molecular weight (an), weight average molecular weight (ai,), and polydispersity (ai,/Mn) giving molecular weight distribution (MWD). In general, a reduction in DP from the pulp stage to the final filament stage was noticed. Maximum degradation was observed to take place during xanthation and not during aging as sometimes claimed. Among the four methods used for gel permeation chromatography (GPC), Universal calibration HDV method, not involving viscosity measurement, gave the best and most reproducible values.

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