Polydimethylsiloxane mass

PDMS = polydimethylsiloxane. PA = polyacrylate. CW = Carbowax. DVB = divinylbenzene. FID = flame ionization detection. NPD = nitrogen-phosphorus detection. TSD = thermionic-specific detection. LOQ = limit of quantitation. LOD = limit of detection. TCA = trichloroacetic acid. PICI-MS = positive ion chemical mass spectrometry. SIM = selected ion monitoring. 

In the 1990s, Pawliszyn [3] developed a rapid, simple, and solvent-free extraction technique termed solid-phase microextraction. In this technique, a fused-silica fiber is coated with a polymer that allows for fast mass transfer—both in the adsorption and desorption of analytes. SPME coupled with GC/MS has been used to detect explosive residues in seawater and sediments from Hawaii [33]. Various fibers coated with carbowax/divinylbenzene, polydimethylsiloxane/divinylbenzene, and polyacrylate are used. The SPME devices are simply immersed into the water samples. The sediment samples are first sonicated with acetonitrile, evaporated, and reconstituted in water, and then sampled by SPME. The device is then inserted into the injection port of the GC/MS system and the analytes thermally desorbed from the fiber. Various... 

Triacetone triperoxide (TATP) is a powerful explosive manufactured in clandestine laboratories and used by terrorists. As TATP subHmes easily, analysis was performed by SPME trapping of its vapor, using polydimethylsiloxane/divinyl benzene (PDMS/DVB) fiber, followed by desorption into a GC/MS injector [10]. Figure 6 shows the TIC, mass chromatogram and the El mass spectmm of headspace from a debris sample containing TATP [11]. The El mass spectmm contains a molecular ion at m/z 222 and several fragment ions. In the chemical ionization mass spectmm of TATP [12], the m or ions were at m/z 223 (100%), 222 (20%), 133 (20%), 117 (40%), 115 (20%), 103 (75%) and 100 (50%). 

For this work, a 5 meter x 50 micron ID fused silica column, coated with a 0.25 micron polydimethylsiloxane film was introduced directly into the source chamber through the transfer line normally used for GC/FTMS. A restrictor was created at the end of the column by using a microflame to draw out the end of a 1 meter portion of deactivated but uncoated column to an inside diameter of approximately one micron. Details of the instrumentation used for SFC have been described elsewhere [19]. With the SFC interface in place, pressures in the source chamber were approximately 5 x 10 5 torr. Despite this high source cell pressure, we were able to obtain relatively high quality mass spectral data with analyzer side detection at 5 x 10"7 torr. 

A cyclic polydimethylsiloxane was also prepared by the end-to-end reaction, i.e., a,ft)-dianion-functionalized polymers, which are then cyclized simply by reaction with a difunctional electrophile to give a cyclic polymer. The cyclic polydimethylsiloxane was synthesized from a commercially available o. tw-dihydroxy-polydimethylsiloxane (M = 2.460 g/mol). The Unear precursor was deprotonated using sodium hydride in dilute THF (< 10 2 M) and then end-coupled using a dichlorosilane coupUng agent (Fig. 53). The uncy-clized anionic linear precursors are then removed by a macroporous anion exchange resin. The successful cyclization and purification is monitored by IR and 29Si NMR, GPC, and MALDI-TOF mass [176],... 

Gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) analyses GC analyses are performed on a WCOT (wall-coated open tubular) polydimethylsiloxane fused silica capillary column (1 fim film thickness, 50m x 0 32mm ID ) Shorter columns for example 25m, or columns with thinner films, for example 0 2/im, may also be used successfully Injection of the silylated sample (2/d) is performed with a moving needle-type injector, other types of capillary GC injection systems may be used after optimization of the concentration and amount of sample to be injected With a 50-m capillary... 

Abstract This paper proposes new ways of preparation of hybrid silicones, i.e. an alternated multiblock seqnence of silicone and alkyl spacers, via a polycondensation process catalyzed by the tris(pentaflnorophenyl)borane, a water-tolerant Lewis acid, between methoxy and hydrogeno fnnctionalized silanes and siloxanes at room temperature and in the open air. The protocol was first developed with model molecules which led to polydimethylsiloxane (PDMS) chains, in order to seize the best experimental conditions. Several factors were studied such as the contents of each reactants, the nature of the solvent or the rate of addition. The best conditions were then adapted to the synthesis of hybrid silicones, condensing alkylated oligo-carbosiloxanes with methoxy or hydrogeno chain-ends and complementary small molecules. A systematic limitation in final molar masses of hybrid silicones was observed and explained by the formation of macrocycles, which cannot redistribnte or condense further while formed. 

In the membrane introduction ion trap MS (MIMS) technique, a membrane composed of a microporous polypropylene hollow support fiber coated with an ultrathin ca 0.5 p,m) polydimethylsiloxane layer serves as the interface between the sample and the vacuum chamber of the mass spectrometer. The simultaneous diffusion of volatile and semivolatUe compounds through the ultrathin polydimethylsiloxane MIMS membrane is one of the method s strengths, in that all the analytical information is obtained in a relatively short time (in the order of seconds to minutes). Lead and nickel / -diketonates could be detected by the MIMS technique. ... 

Calculate the variation in entropy corresponding to a polydimethylsiloxane network of mass 6.89 g, with an average molecular weight between crosslinks Me = 8.3 X 10, subjected to a reversible uniaxial extension at 25°C until the length is double its initial length. 

Investigation of a wide range of block copolymers, consisting of various flexible (polydimethylsiloxane, polybutadiene) and rigid (polycarbonate, polysulphone, polyarylate) phases [44], shows that irrespective of the chemical nature of copolymer, content and molecular weight of blocks as well as pressure and composition of the hydrocarbon mixture, sorption, and mass transfer of alkanes take place primarily in the rubbery phase. The phenomenon of plasticization of polymers by hydrocarbons was demonstrated by baromechanical methods [7,45 8]. Figure 9.13 shows baromechanical curves for the block copolymer... 

In the early 90s, a new technique called solid-phase-micro extraction (SPME), was developed (Arthur and Pawliszyn, 1990). The key-part component of the SPME device is a fused silica fiber coated with an adsorbent material such as polydimethylsiloxane (PDMS), polyacrylate (PA) and carbowax (CW), or mixed phases such as polydimethylsiloxane-divinylbenzene (PDMS-DVB), carboxen-polydimethylsiloxane (CAR-PDMS) and carboxen-polydimethyl-siloxane-divinylbenzene (CAR-PDMS-DVB). The sampling can be made either in the headspace (Vas et al., 1998) or in the liquid phase (De la Calle et al., 1996) of the samples. The headspace sampling in wine analyses is mainly useful for quantifying trace compounds with a particular affinity to the fiber phase, not easily measurable with other techniques. Exhaustive overviews on materials used for the extraction-concentration of aroma compounds were published by Ferreira et al. (1996), Eberler (2001), Cabredo-Pinillos et al. (2004) and Nongonierma et al. (2006). Analysis of the volatile compounds is usually performed by gas chromatography (GC) coupled with either a flame ionization (FID) or mass spectrometry (MS) detector. 

Dastgir et al. [141] coated a polyvinyhdenfluoride microporous support with a thin nonporous polydimethylsiloxane for SLM removal of phenol from wastewater. The choice of support material was based on favorable mass-transfer characteristics and the chemical resistance criteria. 

Values of second virial coefficient (yl2) of a polydimethylsiloxane gum of molar mass (M) 4.43x10 g/mol in several solvents are given below along with data of molar volumes (Vi) at room temperature. 

Mixtures of polymer chain belonging to the same chemical species but with different isotopic compositions (deuterated and non-deuterated) have been widely used for experimental studies of polymer structures, since good neutron beams became available. This technique, combining the preparation of adequate samples and neutron scattering experiments, enabled the experimentalists to determine the size of polymer chains (polystyrene or polydimethylsiloxane), in all kinds of polymer mixtures or concentrated polymer solutions. However, the technique relies on the fact that the deuterated and non-deuterated isotopic varieties of a same polymer are compatible with one another. It is admitted that under the experimental conditions described above, the mixture constitutes a unique phase. In fact, the mixing energy of deuterated and non-deuterated chains is probably very small. However, it is non-zero, in particular, because of differences in atomic volumes and polarizabilities. Thus, there is no doubt that demixtion may occur in mixtures of deuterated and undeuterated chains of very high molecular masses. 

AA, aromatic amine TMA, trimethylamine CINA, chloronitroanilina ClAA, chlorinated aromatic amine LMMA, low molecular mass amine HA, heterocyclic amine PE, polyethylene PS/DVB, polystyrene-divinylbenzene PDMS, polydimethylsiloxane PA, polyacrylate PAB, polyacrilonitrilbutadiene CW, carbowax TPR, templated resin F, food samples. 

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