High-Throughput Automated Parallel Evaluation of Zinc-Based Catalysts for the Copolymerization of CHO and CO 2 to Polycarbonates Wouter J. van Meerendonk, 1 Robbert Duchateau, 1 Cor E. Koning, 1 Gert-Jan M. Gruter* 2 1 Laboratory of Polymer Chemistry, Eindhoven University of Technology and Dutch Polymer Institute, P.O. Box 513, 5600 MB Eindhoven, The Netherlands 2 Avantium Technologies, Zekeringstraat 29, 1014 BVAmsterdam, The Netherlands Fax: þ31(0)20-5868085; E-mail: gert-jan.gruter@avantium.nl Received: November 11, 2003; Revised: November 21, 2003; Accepted: November 24, 2003; DOI: 10.1002/marc.200300255 Keywords: carbon dioxide; catalysis; copolymerization; high-throughput experimentation; parallel synthesis Introduction Although the physical properties of aliphatic polycarbonates do not yet approach the good impact strength, heat resistance and transparency of commercially available poly-(bisphe- nol-A carbonate), [1] they are accessible by a very attractive route, a metal-catalyzed copolymerization of CO 2 and an oxirane. [2] This process is much more environmentally friendly than the two routes currently used for the com- mercial production of aromatic polycarbonates. [1] Carbon dioxide (Scheme 1) is a readily available, cheap, nonflamm- able, nontoxic and renewable monomer. [3] The chain-growth mechanism of this process allows a much higher control of the molecular weight and unlike step-growth processes con- versions do not have to approach 100% in order to obtain high-molecular-weight products. Since the discovery by Inoue et al., [4] extensive effort has been put into the develop- ment of more active catalysts that allow a better control over the polymerization process. [5] Good examples are the zinc phenoxide complexes developed by Darensbourg et al. [6] and the aluminum and chromium porphyrine complexes developed by the group of Inoue and Mang and co-workers, respectively. [7] A system of specific interest was developed by the group of Coates and consists of b-diiminato zinc complexes. [8] These species show high activity and selecti- vity in CHO–CO 2 copolymerizations. More importantly, relatively low pressures (5 –10 bar) are required as compar- ed with the 80–120 bar needed for most other systems. [5] In this communication we like to demonstrate that a high-throughput approach towards further development and fine tuning of these copolymerizations is feasible with the current state of the art equipment available on the market, allowing a significant efficiency increase. Experimental Part Materials Cyclohexene oxide (Aldrich) was dried over CaH 2 , distilled and stored under argon on molsieves (4 A ˚ ) prior to use. Carbon dioxide (> 99.9993% pure) was purchased from HoekLoos. Toluene was dried over an alumina column and stored on molsieves. The b-diiminato (BDI) zinc catalysts [HC(C(CH 3 )- N-2,6-R-C 6 H 3 ) 2 ]Zn–N(SiMe 3 ) 2 (R ¼ Et (1), iPr (2)) were syn- thesized according to literature procedures. [9] Instruments 1 H NMR spectra were recorded on a Varian Gemini 2000 (300 MHz) and a Varian Mercury Vx (400 MHz) spectrometer. Size Exclusion Chromatography (SEC) spectra were recorded Summary: Copolymerization of CO 2 and oxiranes using high-pressure autoclaves typically allows one experiment per reactor per day. As a high-throughput approach for this chemistry would be extremely valuable, a parallel setup has been validated for the copolymerization of CO 2 and cyclohexene oxide (CHO) with two b-diiminato zinc complexes. Molecular weights, polydispersities and acti- vities were found to be comparable with literature values. Polycarbonate from cyclohexene oxide (CHO) and CO 2 . Macromol. Rapid Commun. 2004, 25, 382–386 DOI: 10.1002/marc.200300255 ß 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 382 Communication