Semi‐Batch Copolymerization of Propylene Oxide and Carbon Dioxide

Abstract

Summary: A nanoscopic heterogeneous catalyst system based on zinc glutarate is used to prepare poly(propylene carbonate) (PPC) from CO 2 and propylene oxide (PO). The catalyst was exposed to a defined humid atmosphere. The water uptake resulted in a deactivation to a minimum of 25% of the original activity, depending on time of exposure and water concentration. In addition, the progress of the copolymerization at constant pressure was monitored by measuring the CO 2 uptake. It is shown that the rate is linear with time after an initial phase and that this rate is in linear correlation with the amount of catalyst. The copolymerization was also performed in several modes of discontinuous addition of PO. The productivity of the catalyst was in the range of 1.6-2.0 kg PPC/g Zn, the highest productivity reported for the zinc carboxylate catalyst system so far. High molecular weights of around 220 kg/mol (M w ) and low polydispersities of 2.2-2.5 were achieved in all experiments.

Catalytic Chain Transfer Copolymerization of Propylene Oxide and CO2 using Zinc Glutarate Catalyst

“…The evaluation of the data thus is elaborate. For that reason rate constants were not extracted although this is fundamentally possible …”

“…Similar is observed for the activity of the system under CCTC conditions after the induction time has passed. The monomer depletion does not appear to significantly influence the TOF at conversions lower than a critical value, like was found in previous studies of the nanoscopic ZnGA catalyst . Deactivation of the catalyst was not of importance in that regard, and as it now turns out, molecular weight and concomitant inherent changes in the medium may influence the rate of copolymerization.…”

“…For that reason rate constants were not extracted although this is fundamentally possible. [102] Data from both methods of reaction-monitoring indicate an initial period of little or no monomer conversion. The propagation rate increases substantially after this phase of inactivity.…”

“…The monomer depletion does not appear to significantly influence the TOF at conversions lower than a critical value, like was found in previous studies of the nanoscopic ZnGA catalyst. [102] Deactivation of the catalyst was not of importance in that regard, and as it now turns out, molecular weight and concomitant inherent changes in the medium may influence the rate of copolymerization. It is found that the TOF in the first phase generally remains longer at the higher initial level, corresponding to a higher PO conversion upon addition of BPA.…”

DMC-Mediated Copolymerization of CO2 and PO—Mechanistic Aspects Derived from Feed and Polymer Composition

“…DMCs as catalyst for copolymerization of PO and CO 2 may form cyclic propylene carbonate (cPC) as a side product. The amount of cPC in the final polymer is therefore dependent on process conditions such as temperature, type, and amount of catalysts [82,83]. The dominant formation is a result of a backbiting (unzipping) reaction of a corresponding, free uncoordinated alcohol chain, and proceeds from the chain end.…”