02078nas a2200229 4500008004100000022001400041245013900055210006900194260007300263300001200336490000800348520116000356653001901516653002001535653005001555653002501605653001801630653003601648100002001684700002101704856012301725 2014 eng d a0926-860X00aEffects of method of preparation on catalytic activity of Co-Zn double-metal cyanide catalysts for copolymerization of CO2 and epoxide0 aEffects of method of preparation on catalytic activity of CoZn d aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcJUL a300-3080 v4823 a

Co-Zn double-metal cyanide (DMC) complexes are well-known catalysts for ring-opening polymerization of epoxides and co-polymerization of CO2 and epoxides. This work provides an insight on structure-activity relationship of DMC for poly(cyclohexene carbonate) synthesis. Seven samples of DMC were prepared by different methods and mode of reagent addition. Highly active catalyst could be synthesized even without using a co-complexing agent. CO2 adsorption studies revealed that higher the guest-host interaction higher would be the catalytic activity. High density and strength of Lewis acid sites, moderate crystallinity, low crystal symmetry (rhombohedral/monoclinic), Cl- ions and coordinated tert.-butanol (complexing agent) control the catalytic activity for polycarbonates. Chloride in the structure avoided induction period by increasing acidity of the catalyst and thereby, improving the guest-host interactions. Polycarbonates with CO2 incorporation as high as 86 mol%, average molecular weight of 20900 and polydispersity index of 1.8 were prepared at complete conversion of cyclohexene oxide. (C) 2014 Elsevier B.V. All rights reserved.

10aCarbon dioxide10aCO2 utilization10aCopolymerization of CO2 and cyclohexene oxide10aDouble-metal cyanide10aPolycarbonate10aStructure-activity relationship1 aSebastian, Joby1 aSrinivas, Darbha uhttp://library.ncl.res.in/content/effects-method-preparation-catalytic-activity-co-zn-double-metal-cyanide-catalysts-001963nas a2200217 4500008004100000022001400041245011300055210006900168260010100237300001200338490000800350520108300358653002801441653002001469653003301489653002801522653002801550100002001578700002101598856012601619 2014 eng d a0974-362600aSolid, double-metal cyanide catalysts for synthesis of hyperbranched polyesters and aliphatic polycarbonates0 aSolid doublemetal cyanide catalysts for synthesis of hyperbranch aC V RAMAN AVENUE, SADASHIVANAGAR, P B \#8005, BANGALORE 560 080, INDIAbCatalysis Soc IndiacMAR a499-5090 v1263 a

Fe-Zn and Co-Zn double-metal cyanide (DMC) complexes exhibit highly efficient and selective catalytic activity for synthesis of hyperbranched polyesters (glycerol succinic acid (G-SA) and glycerol adipic acid (G-AA)) and aliphatic polycarbonates (via., alternative co-polymerization of cyclohexene oxide and CO2), respectively. The influence of method of preparation of DMC, in particular the mode of addition of reagents, on its physicochemical and catalytic properties was investigated. Co-Zn DMC was found highly selective for polycarbonate (than polyethers) formation. Catalysts prepared using tert-butanol and PEG-4000 as complexing and co-complexing agents, respectively, were found superior to those prepared without these agents. Apart from its role as a coordinating ligand, tert-butanol activated the Lewis acidic Zn2+ sites for reactions in polyester and polycarbonate formation. Hydrophobicity, micro-mesoporosity, acid strength and the amount of coordinated complexing agent are some of the crucial factors influenced the catalytic activity of DMC complexes.

10aaliphatic polycarbonate10aCO2 utilization10aDouble-metal cyanide complex10aheterogeneous catalysis10ahyperbranched polyester1 aSebastian, Joby1 aDarbha, Srinivas uhttp://library.ncl.res.in/content/solid-double-metal-cyanide-catalysts-synthesis-hyperbranched-polyesters-and-aliphatic-001774nas a2200205 4500008004100000022001400041245013400055210006900189260007300258300001200331490000800343520094400351653002001295653004101315653002501356653001801381100002001399700002101419856012801440 2015 eng d a0926-860X00aFactors influencing catalytic activity of Co-Zn double-metal cyanide complexes for alternating polymerization of epoxides and CO20 aFactors influencing catalytic activity of CoZn doublemetal cyani aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcOCT a163-1720 v5063 a

Co-Zn double-metal cyanides (DMCs) show good catalytic activity towards copolymerization of epoxides and CO2. A deep insight into the structural aspects of the catalysts that control their catalytic performance is addressed in this work. Method of preparation of DMC catalysts was found to have influence on their structure, which in turn dictated their catalytic activity. Complexing agent (t-BuOH) and density of strong acid sites of DMC catalysts were found critical factors responsible for their activity. Selectivity of DMC towards polycarbonates depends on the amount of alkali ion content in their composition. Induction period of the catalysts was governed by the strength of acid sites and by the presence of dispersed ZnCl2 in the composition. This study provides an understanding of the prime features of DMC catalysts that can be tuned for high productivity of polycarbonates. (C) 2015 Elsevier B.V. All rights reserved.

10aCO2 utilization10aCopolymerization of epoxides and CO210aDouble-metal cyanide10aPolycarbonate1 aSebastian, Joby1 aSrinivas, Darbha uhttp://library.ncl.res.in/content/factors-influencing-catalytic-activity-co-zn-double-metal-cyanide-complexes-alternating-0