Said Lubbad

Fast separation of low molecular weight analytes on structurally optimized polymeric capillary monoliths

The optimization of recently introduced tetrakis(4-vinylbenzyl)silane (TVBS)-derived capillary monoliths to suit the fast separation of small molecules was accomplished by simultaneous changes in both the stoichiometry of the polymerization mixture and in the polymerization temperature. Four types of monoliths were prepared by varying the polymerization temperature within 60 and 65 degrees C as well as by changing the monomer content between 15.0 and 20.0 wt.%. Changes in the porosity and morphology of the capillary columns were studied applying inverse size exclusion chromatography (ISEC), nitrogen sorption (BET), and scanning electron microscopy (SEM). All monoliths were used for the reversed-phase separation of various sets of low molecular weight analytes such as alkyl benzenes, aryl amines, carboxylic acids, and a mixture of phenols and carbonyl compounds. Comparable efficiency and performance towards the different sets of analytes were observed. With optimized monolith structures, the fast separation of six-alkyl benzenes was accomplished within less than 2 min. This was made possible by a high linear solvent flow (10mm/s) at low column pressure drops (<15 MPa).

Access to silica- and monolithic polymer supported CC-coupling catalysts via ROMP: applications in high-throughput screening, reactor technology and biphasic catalysis

N ,N -Di(pyrid-2-yl)norborn-2-ene-5-ylcarbamide (1) and N ,N -di(pyrid-2-yl)-7-oxanorborn-2-ene-5-ylcarbamide (3) were used for the synthesis of the corresponding dichloropalladium(II) complexes, N -(norborn-2-ene-5-ylcarboxyl)-N ,N -di(pyrid-2-yl)amine dichloropalladium(II) (2) and N -(7-oxanorborn-2-ene-5-ylcarboxyl)-N ,N -di(pyrid-2-yl)amine dichloropalladium(II) (4), respectively. The structures of 3 and 4 were determined by X-ray crystallography. Using Mo(N -2,6-Me2/C6H3)(CHCMe2Ph)(OCMe(CF3)2)2, 1 was surface-grafted onto various silica-based carriers. Poly-1 was additionally used for the coating of silica and ROMP-derived monolithic supports. Heck systems were generated by loading of the corresponding dipyridylamide-functionalized supports with Pd(II). Alternatively, monolithic Pd-loaded supports were synthesized by an in situ grafting of 4 onto a ROMPderived monolithic support. Finally, 4 was copolymerized with 7-oxanorborn-2-ene-5,6-dicarboxylic anhydride to yield a watersoluble Heck coupling-active copolymer suitable for biphasic catalysis. All supports were successfully tested in the coupling of selected aryliodides and arylbromides under various conditions including flow-through systems, cartridges, biphasic catalysis and microwave-assisted synthesis. Selected data including turn-over numbers (TONs) and frequencies (TOFs) are presented. # 2002 Elsevier Science B.V. All rights reserved.

Monolithic High‐Performance SEC Supports Prepared by ROMP for High‐Throughput Screening of Polymers

Monolithic supports for size exclusion chromatography (SEC) have been synthesized by ring-opening metathesis polymerization and were characterized by means of inverse SEC, Variations in the monoliths compositions were carried out to generate a micro-structure with continuous porosity. Good quantification of the molecular weights of nine narrow polystyrene standards used as unknowns was observed. Analysis times were less than five minutes, offering an attractive access to high-throughput polymer analysis.