Raman spectroscopy polymerization

More recently, Raman spectroscopy has been used to investigate the vibrational spectroscopy of polymer Hquid crystals (46) (see Liquid crystalline materials), the kinetics of polymerization (47) (see Kinetic measurements), synthetic polymers and mbbers (48), and stress and strain in fibers and composites (49) (see Composite materials). The relationship between Raman spectra and the stmcture of conjugated and conducting polymers has been reviewed (50,51). In addition, a general review of ft-Raman studies of polymers has been pubUshed (52). 

In aqueous solution, all the sodium peroxoborates dissociate for the most part into boric acid, or its anion, and hydrogen peroxide. Peroxoborate species are also present in these solutions, depending on the pH and the concentration for the species type. The nature of these species has been extensively examined by classical physicochemical methods (13), by nmr, and by Raman spectroscopy (14—17). Both monomeric and polymeric species are usually present. There is some evidence (18) suggesting that these peroxoborates are more reactive than hydrogen peroxide alone under similar conditions. 

Abstract Molecular spectroscopy is one of the most important means to characterize the various species in solid, hquid and gaseous elemental sulfur. In this chapter the vibrational, UV-Vis and mass spectra of sulfur molecules with between 2 and 20 atoms are critically reviewed together with the spectra of liquid sulfur and of solid allotropes including polymeric and high-pressure phases. In particular, low temperature Raman spectroscopy is a suitable technique to identify single species in mixtures. In mass spectra cluster cations with up to 56 atoms have been observed but fragmentation processes cause serious difficulties. The UV-Vis spectra of S4 are reassigned. The modern XANES spectroscopy has just started to be applied to sulfur allotropes and other sulfur compounds. 

At least five high-pressure allotropes of sulfur have been observed by Raman spectroscopy up to about 40 GPa the spectra of which differ significantly from those of a-Sg at high pressures photo-induced amorphous sulfur (a-S) [57, 58, 109, 119, 184-186], photo-induced sulfur (p-S) [57, 58, 109, 119, 184, 186-191], rhombohedral Se [58, 109, 137, 184, 186, 188, 191], high-pressure low-temperature sulfur (hplt-S) [137, 184, 192], and polymeric sulfur (S ) [58, 109, 119, 193]. The Raman spectra of two of these d-lotropes, a-S and S, were discussed in the preceding section. The Raman spectra of p-S and hplt-S have only been reported for samples at high-pressure conditions. The structure of both allotropes are imknown. The Raman spectrum of Se at STP conditions is discussed below. 

Normal transmission IRLD can also be used to characterize polymeric fibers, although scattering can induce sloping baselines. Raman spectroscopy then becomes a convenient alternative. Rutledge et al. have recently probed the orientation in electrospun nanofibers composed of a core of Bombyx mori fibroin and an outer shell of poly (ethylene oxide) [24], The orientation values were low, less than 0.1, as is often the case in electrospun fibers. 

Emulsion polymerization is used for 10-15% of global polymer production, including such industrially important polymers as poly(acrylonitrile-butadiene-styrene) (ABS), polystyrene, poly(methyl methacrylate), and poly (vinyl acetate) [196]. These are made from aqueous solutions with high concentrations of suspended solids. The important components have unsaturated carbon-carbon double bonds. Raman spectroscopy is well-suited to address these challenges, though the heterogeneity of the mixture sometimes presents challenges. New sample interfaces, such as WAI and transmission mode, that have shown promise in pharmaceutical suspensions are anticipated to help here also. 

Bauer et al. describe the use of a noncontact probe coupled by fiber optics to an FT-Raman system to measure the percentage of dry extractibles and styrene monomer in a styrene/butadiene latex emulsion polymerization reaction using PLS models [201]. Elizalde et al. have examined the use of Raman spectroscopy to monitor the emulsion polymerization of n-butyl acrylate with methyl methacrylate under starved, or low monomer [202], and with high soUds-content [203] conditions. In both cases, models could be built to predict multiple properties, including solids content, residual monomer, and cumulative copolymer composition. Another study compared reaction calorimetry and Raman spectroscopy for monitoring n-butyl acrylate/methyl methacrylate and for vinyl acetate/butyl acrylate, under conditions of normal and instantaneous conversion [204], Both techniques performed well for normal conversion conditions and for overall conversion estimate, but Raman spectroscopy was better at estimating free monomer concentration and instantaneous conversion rate. However, the authors also point out that in certain situations, alternative techniques such as calorimetry can be cheaper, faster, and often easier to maintain accurate models for than Raman spectroscopy, hi a subsequent article, Elizalde et al. found that updating calibration models after... 

C. Galiotis and J. Parthenios, Stress/strain measurements in fibers and composites using Raman spectroscopy, in Vibrational Spectroscopy of Biological and Polymeric Materials, V.G. Gregoriou and M.S. Braiman (Eds), CRC Press, Boca Raton, 2006. 

T.W. Francisco, S. Yembrick and K.W. Leffew, Semi-batch polymerization analysis by mnlti-point Raman spectroscopy, PAT - J. Process Anal. TechnoL, 3, 13-19 (2006). 

C. Bauer, B. Amram, M. Agnely, D. Charmot, J. Sawatzki, M. Dupuy and J.-P. Huvenne, On-hne monitoring of a latex emulsion polymerization by fiber-optic FT-Raman spectroscopy. Part I Cahbration, Appl. Spectrosc., 54, 528-535 (2000). 

O. Elizalde, J.R. Leiza and J.M. Asua, On-hne monitoring of all-acrylic emulsion polymerization reactors by Raman spectroscopy, Macromol. Symp., 206, 135-148 (2004). 

O. Elizalde, M. Azpeitia, M.M. Reis, J.M. Asua and J.R. Leiza, Monitoring emulsion polymerization reactors calorimetry versus Raman spectroscopy, Ind. Eng. Chem. Res., 44, 7200-7207 (2005). 

T.R. McCaffery and Y.G. Durant, Apphcation of low-resolution Raman spectroscopy to onhne monitoring of miniemulsion polymerization, J. Appl. Polym. Sci., 86, 1507-1515 (2002). 

M.M. Reis, P.H.H. Araujo, C. Sayer and R. Giudici, Development of calibration models for estimation of monomer concentration by Raman spectroscopy duiing emulsion polymerization facing the medium heterogeneity, J. Appl. Polym. Sci., 93, 1136-1150 (2004). 

HEMOGLOBINS POLYMERIZATION RESONANCE RAMAN SPECTROSCOPY HEMOGLOBIN-S POLYMERIZATION HENDERSON-HASSELBALCH EQUATION HENDERSON PLOT Henri-Brown treatment,... 

Auguste S, Edwards HGM, Johnson AF et al. (1996) Anionic polymerization of styrene and butadiene initiated by n-butyllithium in ethylbenzene determination of the propagation rate constants using Raman spectroscopy and gel permeation chromatography. Polymer 37 3665-3673... 

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