Mass spectroscopy polymerization

The effects of the feed ratio in the lipase CA-catalyzed polymerization of adipic acid and 1,6-hexanediol were examined by using NMR and MALDI-TOF mass spectroscopies. NMR analysis showed that the hydroxyl terminated product was preferentially formed at the early stage of the polymerization in the stoichiometric substrates. As the reaction proceeded, the carboxyl-terminated product was mainly formed. Even in the use of an excess of the dicarboxylic acid monomer, the hydroxy-terminated polymer was predominantly formed at the early reaction stage, which is a specific polymerization behavior due to the unique enzyme catalysis. 

The degrees of polymerization determined by mass spectroscopy are corroborated by vapor pressure osmometry and gel permeation chromatography studies (21). 

In this study, we extend the range of inorganic materials produced from polymeric precursors to include copper composites. Soluble complexes between poly(2-vinylpyridine) (P2VPy) and cupric chloride were prepared in a mixed solvent of 95% methanol 5% water. Pyrolysis of the isolated complexes results in the formation of carbonaceous composites of copper. The decomposition mechanism of the complexes was studied by optical, infrared, x-ray photoelectron and pyrolysis mass spectroscopy as well as thermogravimetric analysis and magnetic susceptibility measurements. 

A range of tetradentate Schiff-base ligands have also been employed to prepare discrete aluminum alkoxides. The most widely studied system is the unsubstituted parent system (256), which initiates the controlled ROP of rac-LA at 70 °C in toluene. The polymerization displays certain features characteristic of a living process (e.g., narrow Mw/M ), but is only well behaved to approximately 60-70% conversion thereafter transesterification causes the polydispersity to broaden.788 MALDI-TOF mass spectroscopy has been used to show that even at low conversions the polymer chains contain both even and odd numbers of lactic acid repeat units, implying that transesterification occurs in parallel with polymerization in this system.789... 

Wentrup et al. demonstrated the formation of imidoylketene (1214), methyleneketene (1215), and ethynamine (1216) during the flash vacuum pyrolysis (10-5 torr) of isopropylidene aminomethylenemalonate by collision activation mass spectroscopy and 1R spectroscopy (88JA1337). The imidoylketene (1214) appeared first at a pyrolysis temperature of 390°C. As the temperature was increased, the imidoylketene (1214) was rapidly converted into methyleneketene (1215). The formation of ethynamine (1216) was prominent in the temperature range 680-740°C, and it was accompanied by a sharp decrease in the signal of methyleneketene (1215), whereas the imidoylketene (1214) was less affected. Compounds 1214-1216 were stable at -196°C, but they polymerized on warm-up. 

The evidence for this mechanism is based on mass spectroscopy of the gas-phase radiolysis of isobutylene, which may not be applicable to the typical liquid-phase polymerization system. Initiation in condensed systems may follow the same course as electroinitiation— coupling of radical-cations to form dicarbocations. 

Other electrochemical processes of organic compounds on Pb electrodes or electrodes with UPD Pb have been studied - formaldehyde [323], oxalic acid [386], trichloro- and trifluoroethane [387], 1-phenylethylamine [388], 3-hydroxychi-nuclidine [388], dichlorodifluoromethane [389], polychlorobenzenes [390], 1-propa-nol [391], pyrrole polymerization [392], and inorganic compounds - phosphine [388] and sulfate(IV) ions [393]. Simultaneous catalytic or inhibiting influence of organic solvents - acetonitrile, dimethyl-sulfoxide, and Pb + presence on electrooxidation of small organic molecules on Pt electrodes has been studied using on-line mass spectroscopy [394],... 

A very common and useful approach to studying the plasma polymerization process is the careful characterization of the polymer films produced. A specific property of the films is then measured as a function of one or more of the plasma parameters and mechanistic explanations are then derived from such a study. Some of the properties of plasma-polymerized thin films which have been measured include electrical conductivity, tunneling phenomena and photoconductivity, capacitance, optical constants, structure (IR absorption and ESCA), surface tension, free radical density (ESR), surface topography and reverse osmosis characteristics. So far relatively few of these measurements were made with the objective of determining mechanisms of plasma polymerization. The motivation in most instances was a specific application of the thin films. Considerable emphasis on correlations between mass spectroscopy in polymerizing plasmas and ESCA on polymer films with plasma polymerization mechanisms will be given later in this chapter based on recent work done in this laboratory. 

In this article perdeuterated MMA was polymerized with un-deuterated BuLi and the resultant polymer and oligomer were studied for the initiator fragment by using NMR spectroscopy (7a). The undeuterated monomer was also polymerized with BuLi in toluene at -78°C and chromatography and each fraction was analyzed by NMR and mass spectroscopies (7b). The formation of butane in this polymerization reaction was also studied in some detail (7c). 

The mass spectroscopy clearly demonstrated that the oligomer molecule contained one butyl isopropenyl ketone unit at the chain end. The possibility that the ketone unit locates at the chain end of the polymer may be rejected because the low molecular polymer obtained in the lOmin polymerization also contained one ketone unit similarly to the high polymer. 

G.C. analysis. All the samples have been identified by NMR, mass spectroscopy, I.R. and G.C. With this information in mind, it is believed that other systems, such as lithium morpholinide initiator, lithium morpholinide-metal alkoxide, etc., follow the same polymerization mechanism. 

Time-of-flight secondary ion mass spectroscopy (TOF-SIMS)15 has been used for observing the initiating species in anionic ring-opening polymerizations of D3. The PDMS mass spectrum shows peaks of varying intensity with local maxima every 3 silicon repeat units. This distribution is attributed to the relative concentrations of the three initiating species, II, 12 and 13, shown in equation 2 which can be determined from the peak intensities. 

The mechanisms of the oxidation of solvents such as THF and PC were studied by several groups, utilizing FTIR and XPS spectroscopy [107-109] and on-line mass spectrometry (DEMS-differential, electrochemical mass spectroscopy [110-112]). For example, using ex situ FTIR spectroscopy, Lacaze et al. [46] showed that THF in FiC104 solutions are polymerized on electrodes biased to high potentials. The proposed mechanism involves oxidation of C104 as an initial step, as shown in Scheme 7 [46,102], ESR measurements also support such a mechanism. However, there are also suggestions for possible direct oxidation... 

The ionization of an organic molecule is the basic principle of mass spectroscopy however, it should be recognized that mass spectroscopy of a simple molecule such as ethane generally shows multiple ions, covering the fragmented species to partially polymerized species, which indicates that the dissociation of the molecule and some extent of polymerization of fragmented species occurred in the mass spectrometer. The presence of the DG (cathode glow) in DC cathodic polymerization implies that the formation of chemically reactive species via ionization, as depicted by Eq. (4.1), is a very unlikely primary event under the conditions of LCVD. 

Recently two ponderous papers appeared by Kriz and Marek which purported to be model studies of the cationk polymerization of isobutylene 11,12). In the first phase of their study 11) the authors chose 1,1 -dineopentyl ethylene, a trimer of isobutylene, as their model compound and worked with AlBrj, HBr (or DBr) in n-heptane at —70° 11). They mixed these reagents by the following s uenc nC -nHBr + trimer-HAlBr3. The products were analyzed by gas chromatography, NMR (60 MHz), and mass spectroscopy. Usefiil, hard data of this research are as follows 1.1,1-dineopentylethylene rapidly isomerizes... 

Divalent samarocene complexes also show unique reactivity toward a-olefins [55]. Bis-Cp complexes of type 13 display high polymerization activity toward ethylene, but yield rather low molecular weights (M < 25 000) [56]. The polymerization mechanism was investigated using field desorption mass spectroscopy (FD-MS) and proposed as outlined in Scheme 2. A 2 1 complex of 13 with ethyl-... 

---