DMC-Mediated Copolymerization of CO<sub>2</sub> and PO—Mechanistic Aspects Derived from Feed and Polymer Composition
The influence of composition of liquid phase on composition of poly(propylene ether carbonates) in the copolymerization of CO<sub>2</sub> with propylene oxide (PO), mediated by a zinc chloride cobalt double metal cyanide, was monitored by FT-IR/CO<sub>2</sub> uptake/size excl...
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doaj-973989174bcd4daeb8834f57857312df2020-11-25T03:04:26ZengMDPI AGCatalysts2073-43442020-09-01101066106610.3390/catal10091066DMC-Mediated Copolymerization of CO<sub>2</sub> and PO—Mechanistic Aspects Derived from Feed and Polymer CompositionSarah-Franziska Stahl0Gerrit A. Luinstra1Institute for Technical and Macromolecular Chemistry, University of Hamburg, Bundesstr. 45, 20146 Hamburg, GermanyInstitute for Technical and Macromolecular Chemistry, University of Hamburg, Bundesstr. 45, 20146 Hamburg, GermanyThe influence of composition of liquid phase on composition of poly(propylene ether carbonates) in the copolymerization of CO<sub>2</sub> with propylene oxide (PO), mediated by a zinc chloride cobalt double metal cyanide, was monitored by FT-IR/CO<sub>2</sub> uptake/size exclusion chromatography in batch and semi-batch mode. The ratio of mol fractions of carbonate to ether linkages <i>F</i> (~0.15) was found virtually independent on the feed between 60 and 120 °C. The presence of CO<sub>2</sub> lowers the catalytic activity but yields more narrowly distributed poly(propylene ether carbonates). Hints on diffusion and chemistry-related restrictions were found underlying, broadening the distribution. The incorporation of CO<sub>2</sub> seems to proceed in a metal-based insertion chain process, ether linkages are generated stepwise after external nucleophilic attack. The presence of amines resulted in lower activities and no change in <i>F</i>. An exchange of chloride for nitrate in the catalyst led to a higher <i>F</i> of max. 0.45. The observations are interpreted in a mechanistic scheme, comprising surface-base-assisted nucleophilic attack of external weak nucleophiles and of mobile surface-bound carboxylato entities on activated PO in competition to protonation of surface-bound alkoxide intermediates by poly(propylene ether carbonate) glycols or by surface-bound protons. Basic entities on the catalyst may promote CO<sub>2</sub> incorporation.https://www.mdpi.com/2073-4344/10/9/1066double metal cyanide catalysisring-opening polymerizationpoly(propylene ether carbonate), PPECheterogeneous catalysispropylene oxidecarbon dioxide |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Sarah-Franziska Stahl Gerrit A. Luinstra |
spellingShingle |
Sarah-Franziska Stahl Gerrit A. Luinstra DMC-Mediated Copolymerization of CO<sub>2</sub> and PO—Mechanistic Aspects Derived from Feed and Polymer Composition Catalysts double metal cyanide catalysis ring-opening polymerization poly(propylene ether carbonate), PPEC heterogeneous catalysis propylene oxide carbon dioxide |
author_facet |
Sarah-Franziska Stahl Gerrit A. Luinstra |
author_sort |
Sarah-Franziska Stahl |
title |
DMC-Mediated Copolymerization of CO<sub>2</sub> and PO—Mechanistic Aspects Derived from Feed and Polymer Composition |
title_short |
DMC-Mediated Copolymerization of CO<sub>2</sub> and PO—Mechanistic Aspects Derived from Feed and Polymer Composition |
title_full |
DMC-Mediated Copolymerization of CO<sub>2</sub> and PO—Mechanistic Aspects Derived from Feed and Polymer Composition |
title_fullStr |
DMC-Mediated Copolymerization of CO<sub>2</sub> and PO—Mechanistic Aspects Derived from Feed and Polymer Composition |
title_full_unstemmed |
DMC-Mediated Copolymerization of CO<sub>2</sub> and PO—Mechanistic Aspects Derived from Feed and Polymer Composition |
title_sort |
dmc-mediated copolymerization of co<sub>2</sub> and po—mechanistic aspects derived from feed and polymer composition |
publisher |
MDPI AG |
series |
Catalysts |
issn |
2073-4344 |
publishDate |
2020-09-01 |
description |
The influence of composition of liquid phase on composition of poly(propylene ether carbonates) in the copolymerization of CO<sub>2</sub> with propylene oxide (PO), mediated by a zinc chloride cobalt double metal cyanide, was monitored by FT-IR/CO<sub>2</sub> uptake/size exclusion chromatography in batch and semi-batch mode. The ratio of mol fractions of carbonate to ether linkages <i>F</i> (~0.15) was found virtually independent on the feed between 60 and 120 °C. The presence of CO<sub>2</sub> lowers the catalytic activity but yields more narrowly distributed poly(propylene ether carbonates). Hints on diffusion and chemistry-related restrictions were found underlying, broadening the distribution. The incorporation of CO<sub>2</sub> seems to proceed in a metal-based insertion chain process, ether linkages are generated stepwise after external nucleophilic attack. The presence of amines resulted in lower activities and no change in <i>F</i>. An exchange of chloride for nitrate in the catalyst led to a higher <i>F</i> of max. 0.45. The observations are interpreted in a mechanistic scheme, comprising surface-base-assisted nucleophilic attack of external weak nucleophiles and of mobile surface-bound carboxylato entities on activated PO in competition to protonation of surface-bound alkoxide intermediates by poly(propylene ether carbonate) glycols or by surface-bound protons. Basic entities on the catalyst may promote CO<sub>2</sub> incorporation. |
topic |
double metal cyanide catalysis ring-opening polymerization poly(propylene ether carbonate), PPEC heterogeneous catalysis propylene oxide carbon dioxide |
url |
https://www.mdpi.com/2073-4344/10/9/1066 |
work_keys_str_mv |
AT sarahfranziskastahl dmcmediatedcopolymerizationofcosub2subandpomechanisticaspectsderivedfromfeedandpolymercomposition AT gerritaluinstra dmcmediatedcopolymerizationofcosub2subandpomechanisticaspectsderivedfromfeedandpolymercomposition |
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