The Unique Versatility of the Double Metal Cyanide (DMC) Catalyst: Introducing Siloxane Segments to Polypropylene Oxide by Ring‐Opening Copolymerization

Abstract

The combination of hydrophobic polydimethylsiloxane (PDMS) blocks with hydrophilic polyether segments plays a key role for silicone surfactants. Capitalizing on the double metal cyanide (DMC) catalyst, the direct (i.e., statistical) copolymerization of cyclic siloxanes and epoxides is shown to be feasible. The solvent‐free one‐pot copolymerization of hexamethylcyclotrisiloxane and propylene oxide results in the formation of gradient propylene oxide (PPO)‐PDMS copolymers. Copolymers with up to 46% siloxane content with low dispersities (Ð < 1.2) are obtained in the molecular weight range of 2100–2900 g mol–1. The polymerization kinetics are investigated by pressure monitoring and in situ 1H and in situ 29Si NMR spectroscopy. Contact angle measurements reveal the impact of siloxane incorporation manifest in strongly increased hydrophobicity of PPO‐PDMS copolymers and a glass transition of −95 °C for 46% SiO content. This unusual copolymerization offers promise for the synthesis of silicone/polyether polyols.

Unexpected Random Copolymerization of Propylene Oxide with Glycidyl Methyl Ether via Double Metal Cyanide Catalysis: Introducing Polarity in Polypropylene Oxide

“…Initially, we investigated the pressure progression of the DMC-catalyzed copolymerization of PO and GME, initiated by 2-(benzyloxy)­ethanol. In situ pressure monitoring enabled us to obtain one data point per 100 ms. Fast data collection is crucial, taking the explosive pressure increase during DMC catalysis known in the literature into account. , All polymerizations were performed at 120 °C using the same amount of the volatile PO for all polymerizations. This procedure enabled the use of a constant reaction volume, which ensures comparability of all pressure curves.…”

“…Nevertheless, one has to keep in mind that induction periods in DMC-catalyzed polymerizations are independent of reaction parameters to some extent. They depend on several factors and have been observed to vary extensively from 5 min up to 1 h . Induction times of polymerizations can be decreased not only by the increase of temperature and catalyst level but also by the fragmentation rate of the catalyst particles. ,, Hence, the polymerizations were analyzed by their curve progression, maximum pressure p max , the rate of pressure increase after the turning point indicating the induction period Δ t ind and the slope of the pressure decrease m rather than the induction time t max (Table ).…”

Borane catalysis for epoxide (co)polymerization

“…Especially copolymerization with CO 2 , generating polycarbonates, 29–33 and with anhydrides, yielding polyesters, 34,35 will be a point of interest in this review, but many more examples could be mentioned. 36–41…”

Borinane Boosted Bifunctional Organocatalysts for Ultrafast Ring-Opening Polymerization of Cyclic Ethers

“…The aluminum-based Vandenberg catalyst which implies monomer coordination before insertion affords high molar mass PPO but the polymerization is not well controlled. Even zinc/cobalt double metal cyanide (DMC) − catalyst which is employed for PPO production in industries is not without drawbacks such as long induction time, specific equipment to meet harsh polymerization conditions (high temperature and pressure buildup during polymerization), high molar mass impurities (100–400 kg/mol), necessity of specific chain transfer agents (CTAs), and unsuitability for ring-opening polymerization (ROP) of EO. Other outstanding metallic catalysts have been specially designed for the synthesis of PPO by Coates − and Deffieux, − respectively.…”