Synthesis and properties of high-temperature mesomorphic polysiloxane (MEPSIL) solvents: biphenyl- and terphenyl-based nematic systems

Abstract

The synthesis and characterization of a variety of mesomorphic (liquid-crystalline) side-chain polysiloxane (MEPSIL) solvents, said to be useful as gas chromatographic stationary phases, are described and discussed. The synthetic scheme is based upon the hydrosilatlon reaction that occurs when 4-(allyloxy)benzoyl esters are contacted with poly(methylslloxane) In the presence of a dicyclopentadlenylplatinum(II) catalyst, while product characterization Is carried out by IR, NMR, GC, DSC, elemental analysis, and direct-observation hot-stage light-polarized microscopy. Selectivity of the MEPSIL phases Is shown to differ very substantially from those exhibited by all other common GC solvents. The MEPSIL found overall to be the best suited as a GC stationary liquid exhibits a melting point of 139 °C (k -n) and a nematic/isotroplc (n -*-I) transition temperature of 319 °C, while the practical operating limits of the material span 150 to in excess of 300 °C.The development and optimization of chromatographic techniques for maximal resolution in minimal time of analysis, coupled with maximum sample throughput, continue to represent a substantial problem when dealing with analytes comprised of structurally related isomers. Among the most notably difficult of these are polycyclic aromatic hydrocarbons (PAH) which are, at the very least, ubiquitous environmental pollutants produced by the incomplete combustion of organic matter. Moreover, some of the most efficient carcinogens known at present are members of, or products derived directly

Maleimido‐Terminated Self‐Assembled Monolayers

“…Catalyst for hydrosilylation: dicyclopentadienylplatinum(ii) chloride [Cp 2 PtCl 2 ]: Method adopted from reference [38]: hydrated chloroplatinic acid (0.69 g, 1.33 mmol) was dissolved in glacial acetic acid (1.5 mL) in a 25-mL flask. The solution was diluted with water (2.5 mL) and slowly heated to 70 8C.…”

Prospectives of polymeric liquid crystal stationary phases for capillary column gas chromatographic separations

“…All identifications are based on the retention times of standard compounds injected at identical conditions, the mass spectral data of compounds in the sample compared with reference mass spectra, and the elution trend of various compounds on liquid crystal stationary phases in gas chromatography. A little work has been done regarding the application of liquid crystalline stationary phases for the separation of very complex mixtures (17,19,20). Our results show the practical application of capillary columns using a polymeric liquid crystal stationary phase for the separation of a large number of organic compounds in a complex environmental sample of airborne particulate matter.…”

“…The synthesis of new liquid crystalline compounds and separation of disubstituted benzene isomers (13), insect sex pheromones (14), and the effect of the chemical structure of liquid crystalline compounds on separation potential is reported in the literature (8). Recently, polymeric liquid crystals were developed for use in capillary columns (15)(16)(17)(18)(19)(20). These phases can be coated in capillary columns by dynamic or static coating techniques.…”

Control of calcium carbonate crystallization by using anionic polymethylsiloxanes as templates

“…Styrene and MMI were used as unsaturated compounds in the hydrosilylation reaction for the synthesis of SO 3 H-PMS and CO 2 H-PMS, respectively and by using Cp 2 PtCl 2 as catalyst [40,41,77]. Briefly, styrene and/or MMI (15 or 20 mol% excess over the Si-H) was dissolved in 100 ml of sodium-dried, freshly distilled toluene together with the stoichiometric amount of PMS.…”